Co-reporter:Yang Cui, Mei Zhang, Fu-Sheng DuZi-Chen Li
ACS Macro Letters January 17, 2017 Volume 6(Issue 1) pp:
Publication Date(Web):December 14, 2016
DOI:10.1021/acsmacrolett.6b00833
We report the straightforward synthesis of two types of H2O2-cleavable poly(ester-amide)s (P1 and P2) via the Passerini multicomponent polymerization (P-MCP) of 4-formylbenzeneboronic acid pinacol ester with 1,6-diisocyanohexane and 1,6-hexanedioic acid or a polyethylene glycol (PEG) dicarboxylic acid. The H2O2-cleavable phenylboronic acid ester was integrated into the polymer backbone by the in situ formed benzyl ester bond. GPC and 1H NMR confirmed the complete H2O2-triggered degradation of these polymers in aqueous medium by a mechanism of sequential oxidation of phenylboronic acid ester and self-immolative elimination. Compared with the hydrophobic polymer P1, the PEG-based water-soluble polymer P2 degraded much faster even at a lower H2O2 concentration. Cytocompatible nanoparticles of polymer P1 loaded with fluorescent Nile red were fabricated, and controlled release of Nile red in response to H2O2 was achieved, thus, demonstrating the utility of these polymers as potential H2O2-responsive delivery vehicles.
Co-reporter:Zi-Chen Li;Fang-Yi Qiu;Fu-Sheng Du;Mei Zhang
Macromolecules January 10, 2017 Volume 50(Issue 1) pp:23-34
Publication Date(Web):December 21, 2016
DOI:10.1021/acs.macromol.6b01883
Functional polyesters and poly(carbonate)s (PCs) with controlled and on-demand degradation properties have great advantages for biomedical and pharmaceutical applications. Herein, we report a new kind of aliphatic PC that possesses the feature of oxidation promoted degradation. Two six-membered cyclic carbonates (C1 and C2) containing phenylboronic ester group have been synthesized from serinol (1) and 2-aminomethyl-2-methylpropane-1,3-diol (2), respectively. Both monomers could undergo well-controlled ring-opening polymerization (ROP) catalyzed by an organic base, but the 5,5-disubstituted C2 has the character of equilibrium ROP and a much slower rate than the monosubstituted C1. The copolymerization of C1 or C2 with trimethylene carbonate and its derivative leads to a series of copolymers. Two series of amphiphilic block copolymers (BPC1s and BPC2s) have been prepared from C1 and C2 using poly(ethylene glycol) as the macroinitiator. They are able to form nanoparticles with the diameters less than 150 nm. The H2O2-triggered decomposition of C1, C2, and their corresponding noncyclic model compounds was studied by 1H NMR, showing the consecutive process of oxidation, 1,6-elimination, release of CO2, and intramolecular isomerization or cyclization. The degradation of the block copolymer nanoparticles, investigated by 1H NMR, GPC, laser light scattering (LLS), and Nile Red fluorescence, can also be accelerated drastically by H2O2 following the similar mechanism but is affected by steric hindrance of the polymer chain and heterogeneous microenvironment inside the nanoparticles. The results of 1H NMR and LLS reveal that the nanoparticles of BPC1 and BPC2 exhibited different degradation profiles, with a slightly faster degradation rate for BPC2. Of particular interest, BPC2 nanoparticle is sensitive to as low as 0.02 mM H2O2.
Co-reporter:Yu-Huan Wu, Jian Zhang, Fu-Sheng Du, and Zi-Chen Li
ACS Macro Letters December 19, 2017 Volume 6(Issue 12) pp:1398-1398
Publication Date(Web):December 1, 2017
DOI:10.1021/acsmacrolett.7b00863
The selective Passerini reactions of 4-formylbenzoic acid and 4-isocyanobenzoic acid with aliphatic isocyanides and aldehydes were utilized to synthesize sequence-defined uniform macromolecules. Our strategy does not involve any protecting groups or reactive group transformation steps and allows direct and consecutive propagation of sequence in each step. Introduction of diverse side groups by using different aliphatic components provided a range of sequence-defined uniform macromolecules in high yield and gram scale. The strategy also allows further Passerini self-coupling or cross-coupling of the formed sequences with other small molecules, affording polymers with up to 5098.3 Da and 20 side groups. Thus, this strategy will show promise for more efficient synthesis of new sequence-defined macromolecules.
Co-reporter:Shan Su;Fu-Sheng Du
Organic & Biomolecular Chemistry 2017 vol. 15(Issue 39) pp:8384-8392
Publication Date(Web):2017/10/11
DOI:10.1039/C7OB02188G
Maleamic acid derivatives as weakly acid-sensitive linkers or caging groups have been used widely in smart delivery systems. Here we report on the controlled synthetic methods to mono- and dialkyl substituted maleamic acids and their pH-dependent hydrolysis behaviors. Firstly, we studied the reaction between n-butylamine and citraconic anhydride, and found that the ratio of the two n-butyl citraconamic acid isomers (α and β) could be finely tuned by controlling the reaction temperature and time. Secondly, we investigated the effects of solvent, basic catalyst, and temperature on the reaction of n-butylamine with 2,3-dimethylmaleic anhydride, and optimized the reaction conditions to efficiently synthesize the dimethylmaleamic acids. Finally, we compared the pH-dependent hydrolysis profiles of four OEG-NH2 derived water-soluble maleamic acid derivatives. The results reveal that the number, structure, and position of the substituents on the cis-double bond exhibit a significant effect on the pH-related hydrolysis kinetics and selectivity of the maleamic acid derivatives. Interestingly, for the mono-substituted citraconamic acids (α-/β-isomer), we found that their hydrolyses are accompanied by the isomerization between the two isomers.
Co-reporter:Mei Zhang, Cheng-Cheng Song, Ran Ji, Zeng-Ying Qiao, Chao Yang, Fang-Yi Qiu, De-Hai Liang, Fu-Sheng Du and Zi-Chen Li
Polymer Chemistry 2016 vol. 7(Issue 7) pp:1494-1504
Publication Date(Web):14 Jan 2016
DOI:10.1039/C5PY01999K
Oxidation stress has been becoming an important target for the development of smart nanomedicines, triggering research interest in oxidation responsive polymers. Herein, we report a new type of temperature/oxidation dual responsive copolymer. They were synthesized by the sequential atom transfer radical copolymerization (ATRP) of N-isopropylacrylamide (NIPAM, M1) and a phenylboronic pinacol ester-containing acrylate (M2) and dialysis against water to remove the pinacol protecting groups. The copolymers with a small amount of phenylboronic acid units (<7%) were soluble in cold neutral phosphate buffer but showed lower critical solution temperatures in the range of 12–31 °C. The thermally induced phase transition profiles depended on both the composition and concentration of the polymers. The cloud points of the copolymers were shifted to higher temperatures upon H2O2 induced oxidation of the phenylboronic acid and the subsequent 1,6-elimination. Using PEG-Cl as the macroinitiator to initiate ATRP of M1 and M2, three block copolymers composed of a PEG block and a temperature/oxidation dual responsive segment were prepared after dialysis in water. These block copolymers had a similar ratio of NIPAM to phenylboronic acid units but different molecular weights. We have studied their thermal self-assembly and H2O2 triggered decomposition by laser light scattering, 1H NMR, and transmission electron microscopy. Upon a fast heating protocol, these block copolymers formed stable micelle-like nanoparticles (at 37 °C) that were capable of encapsulating doxorubicin (DOX) and showed H2O2 triggered release. The naked nanoparticles were cytocompatible, however the DOX-loaded ones exhibited concentration dependent cytotoxicity, in particular to cancer cells.
Co-reporter:An Lv, Yang Cui, Fu-Sheng Du, and Zi-Chen Li
Macromolecules 2016 Volume 49(Issue 22) pp:8449-8458
Publication Date(Web):November 10, 2016
DOI:10.1021/acs.macromol.6b01325
We report the novel synthesis of thermally degradable polyesters through the postpolymerization modification of an unsaturated aliphatic polyester from maleic acid via Michael addition reaction with β-amino mercaptans. A high molecular weight polyester (P0) was synthesized by the acyclic diene metathesis (ADMET) polymerization of a diene monomer, di(10-undecenyl) maleate. Postpolymerization modification of P0 with three β-amino mercaptans (2-aminoethanethiol, l-cysteine methyl ester, and 2-(butylamino)ethanethiol) and 2-mercaptoethanol via the selective and quantitative thiol–Michael addition reaction with the maleate vinylic double bonds afforded four polyesters (P1–P4). All the polyesters were characterized by 1H NMR, GPC, and MALDI-TOF-MS, and their thermal properties were studied by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The three polymers with pendant amino groups (P1–P3) subjected to thermal-induced degradation in the solid state, the driving force of which is the intramolecular cyclization at elevated temperatures with the formation of six-membered lactam derivatives. Degradation kinetics of P1–P3 in the solid states at different temperatures was studied in detail. It was found that increase of the steric hindrance and decrease of the nucleophilicity of the pendent amino groups could increase the degradation temperatures from 0 °C (P1) to 50 °C (P3). Alternatively, protonation of the amino groups of P1 and P2 with trifluoroacetic acid (TFA) could decrease the nucleophilicity of the primary amino groups, and the polymers P1-Boc and P2-Boc showed enhanced thermal stability up to 80 °C. Degradation of these two polymers via intramolecular cyclization occurred only when TFA was removed at higher temperatures. When the pendant group was a hydroxyl group as in polymer P4, no intramolecular cyclization occurred, and the polymer was thermally stable up 130 °C. Thus, the results highlight the importance of sequence, functional group, and nucleophilicity of the amino groups in determining the intramolecular cyclization and thermal degradation of these polyesters.
Co-reporter:Jian Zhang, Mei Zhang, Fu-Sheng Du, and Zi-Chen Li
Macromolecules 2016 Volume 49(Issue 7) pp:2592-2600
Publication Date(Web):March 31, 2016
DOI:10.1021/acs.macromol.6b00096
We describe a straightforward strategy for a new family of functional polycaprolactones (PCL) via the Passerini multicomponent polymerization (P-MCP) of 6-oxohexanoic acid and various isocyanides. Room temperature polymerization of tert-butyl isocyanide (1), 2,6-dimethylphenyl isocyanide (2), mOEG4 isocyanide (3), 5-isocyanopent-1-ene (4), and 5-isocyanopent-1-yne (5) with 6-oxohexanoic acid in CH2Cl2 generated PCL analogues (P1–P5) with different pendent groups amide-linked to the ε-position of PCL backbone. Furthermore, copolymerization of a mixture of isocyanides 1 and 3 in different molar ratios with 6-oxohexanoic acid produced copolymers (P6–P9) with adjustable properties. To demonstrate the high versatility of this platform polymer, polymer P4 with pendent alkene group was further modified with glucose via the thiol–ene click reaction. The structures of these (co)polymers were confirmed by 1H NMR, 13C NMR, and matrix-assisted laser desorption ionization mass spectroscopy. The thermal properties of these (co)polymers were examined by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). All these polymers are amorphous with variable glass transition temperatures (Tg) depending on the side groups. For the copolymers, the dependence of Tgs on comonomer composition was well predicted by the Fox equation. Degradation of water-soluble polymer P3 in aqueous solutions was investigated by 1H NMR and SEC. It was revealed that P3 was stable in D2O or pD = 5.8 phosphate buffer (PB) up to 15 days, while it completely degraded in basic condition over a period of 6 h and in acidic condition over a period of 24 h. Interestingly, polymer P3 even degraded steadily in pD = 7.4 PB by a random hydrolysis mechanism. Two polymer samples were examined to be nontoxic. Thus, this novel class of PCL analogues can be easily engineered to tailor its material properties and degradation behavior and may have great potential as new degradable materials to meet biomedical applications.
Co-reporter:Fang-Yi Qiu, Cheng-Cheng Song, Mei Zhang, Fu-Sheng Du, and Zi-Chen Li
ACS Macro Letters 2015 Volume 4(Issue 11) pp:1220
Publication Date(Web):October 21, 2015
DOI:10.1021/acsmacrolett.5b00533
We report a new type of oxidation-promoted fast-degradable aliphatic poly(carbonate)s (PCs) prepared by the ring-opening polymerization (ROP) of a six-membered cyclic carbonate containing a phenylboronic pinacol ester. The ROP of this monomer catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) proceeded rapidly at ambient temperature with a good control over molecular weight and polydispersity at high monomer conversion. The H2O2-induced decomposition of this cyclic monomer and its noncyclic carbonate analogue was first studied by 1H NMR in order to clearly demonstrate the degradation mechanism of the PCs. The results of 1H NMR, GPC, and Nile Red fluorescence measurements revealed that the PC nanoparticles formulated by the o/w emulsion method were stable in neutral buffer, but upon triggering with H2O2, they underwent rapid surface degradation via the consecutive processes of oxidation, 1,6-elimination, release of CO2, and intramolecular cyclization. The degradation rates of the nanoparticles were dependent on the concentration of H2O2, and the nanoparticles were even sensitive to 0.5 mM of H2O2.
Co-reporter:Ran Ji, Jing Cheng, Cheng-Cheng Song, Fu-Sheng Du, De-Hai Liang, and Zi-Chen Li
ACS Macro Letters 2015 Volume 4(Issue 1) pp:65
Publication Date(Web):December 24, 2014
DOI:10.1021/mz5007359
We demonstrate a new type of acid-sensitive amphiphilic polypseudorotaxanes (PPRs) formed via inclusion complexation between Pluronic F127 and the hydrophobic β-cyclodextrin (CD) derivative in alcoholic solvents. The 6-OH ortho ester-substituted hydrophobic β-CD derivative (EMD-CD) was prepared by “click” reaction of β-CD with 2-ethylidene-4-methyl-1,3-dioxalane under mild conditions. The water-insoluble EMD-CD (host) is capable of forming PPRs with F127 (guest) in ethanol or methanol but not in water, which is confirmed by 1H NMR, wide-angle X-ray diffraction, small-angle X-ray scattering, and the time-dependent threading kinetics. Depending on the host/guest ratio, the PPRs self-assembled into sheet-like structure or vesicular nanoparticles with different sizes in water. These PPR assemblies were stable at pH 8.4 but quickly dissociated into biocompatible products in neutral or in acidic buffers due to the hydrolysis of the ortho ester groups. Good biocompatibility, ease of fabrication, and extremely pH-sensitive character make the PPRs promising carriers for anticancer drug delivery. Moreover, the present work provides an alternative method for the preparation of PPRs composed of water-insoluble CD derivatives.
Co-reporter:Fang-Yi Qiu;Mei Zhang;Ran Ji;Fu-Sheng Du
Macromolecular Rapid Communications 2015 Volume 36( Issue 22) pp:2012-2018
Publication Date(Web):
DOI:10.1002/marc.201500349
Co-reporter:Zichen Li, Yongming Chen
Polymer 2015 Volume 64() pp:193-195
Publication Date(Web):1 May 2015
DOI:10.1016/j.polymer.2015.03.031
Co-reporter:Yao-Zong Wang, Lei Li, Fu-Sheng Du, Zi-Chen Li
Polymer 2015 Volume 68() pp:270-278
Publication Date(Web):26 June 2015
DOI:10.1016/j.polymer.2015.05.032
•Photo-labile polymers are synthesized by Passerini multicomponent polymerization.•These polymers show dual functions, substrate adhesiveness and UV degradation.•The adhesion performance can be tuned by varying the catechol contents.We report a facile synthetic approach to a new type of catechol containing UV dimantlable adhesive. A series of linear polymers containing pendent catechol moieties and main chain o-nitrobenzyl ester groups were synthesized by the Passerini multicomponent polymerization (MCP) of a di-o-nitrobenzaldehyde, 1,6-diisocyanohexane, 3-(3,4-dihydroxyphenyl) propionic acid, and undecanoic acid. The content of the catechol moieties was adjusted by varying the molar ratio of 3-(3,4-dihydroxyphenyl) propionic acid to undecanoic acid. The thermal properties of these polymers were investigated, they are stable up to 250 °C, and the glass transition temperatures (Tg) are in the range of 17–70 °C. Increasing the catechol content will increase the Tg and slightly decrease the thermal stability. The pendent catechol groups and the in situ formed o-nitrobenzyl ester linkages in the polymer main chain endow the polymer with dual functions, substrate adhesiveness and UV degradation. The UV degradation process was monitored by 1H NMR, GPC, UV–Vis and FTIR. Lap shear strength tests revealed that the adhesion performance of these polymers could be tuned by varying the catechol contents. UV irradiation could cleave the polymer chains, thus decreasing the adhesion strength.
Co-reporter:Cheng-Cheng Song, Fu-Sheng Du and Zi-Chen Li
Journal of Materials Chemistry A 2014 vol. 2(Issue 22) pp:3413-3426
Publication Date(Web):04 Mar 2014
DOI:10.1039/C3TB21725F
Reactive oxygen species (ROS) play key roles in many physiological processes, such as cell signaling and host innate immunity. However, when they are overproduced, ROS may damage biomolecules in vivo and cause diseases such as cardiovascular or neurodegenerative diseases, cancer, and so forth. Oxidative stress is usually implicated in various inflammatory tissues, representing an important target for the development of various therapeutic strategies. Therefore, various probes for the in vitro detection of ROS or the in vivo diagnosis of the oxidative stress-relevant diseases have been developed. Oxidation-responsive polymers have also attracted great interest due to their potential applications in biomedical fields. In this feature article, we summarize six types of oxidation-responsive polymers based on different oxidation-responsive motifs. Poly(propylene sulfide)s, selenium-based polymers, aryl oxalate- and phenylboronic ester-containing polymers are discussed in detail, while poly(thioketal)s and proline-containing polymeric scaffolds are briefly introduced.
Co-reporter:Xin-Xing Deng, Fu-Sheng Du, and Zi-Chen Li
ACS Macro Letters 2014 Volume 3(Issue 7) pp:667
Publication Date(Web):June 20, 2014
DOI:10.1021/mz500207z
Synthesis of dendrimers has been directed toward process efficiency and structural diversity. We report a divergent approach to the preparation of dendrimers with both ABC and ABB branching structures from nonbranching monomers by combination of efficient orthogonal ABC Passerini multicomponent reaction (MCR) and ABB thiol–yne MCR. Two kinds of dendrimers were synthesized efficiently: (1) dendrimers with two generations in three steps and (2) dendrimers with two generations containing one kind of internal functional group and two kinds of surface functional groups in five steps. This new synthetic method offers an efficient access to dendrimers with structural diversity.
Co-reporter:Xin-Xing Deng, Yang Cui, Fu-Sheng Du and Zi-Chen Li
Polymer Chemistry 2014 vol. 5(Issue 10) pp:3316-3320
Publication Date(Web):28 Feb 2014
DOI:10.1039/C3PY01705B
A new synthetic approach to prepare functional highly branched polymers (HBPs) is demonstrated via the multicomponent polymerization (MCP) of easily accessible hexanedioic acid (A2), hexane-1,6-dial (B2), 1,6-diisocyanohexane (C2) and 10-undecenoic acid (A). Both the degree of branching (DB) and the degree of additional functionalization (DF) were regulated by simply varying the ratio of A2 to A.
Co-reporter:Chun-Hao Wang;Zi-Yuan Song;Xin-Xing Deng;Li-Jing Zhang;Fu-Sheng Du
Macromolecular Rapid Communications 2014 Volume 35( Issue 4) pp:474-478
Publication Date(Web):
DOI:10.1002/marc.201300721
Co-reporter:Ting Yang, Ran Ji, Xin-Xing Deng, Fu-Sheng Du and Zi-Chen Li
Soft Matter 2014 vol. 10(Issue 15) pp:2671-2678
Publication Date(Web):08 Jan 2014
DOI:10.1039/C3SM53059K
A novel glucose-responsive hydrogel system based on dynamic covalent chemistry and inclusion complexation was described. Hydrogels are formed by simply mixing the solutions of three components: poly(ethylene oxide)-b-poly vinyl alcohol (PEO-b-PVA) diblock polymer, α-cyclodextrin (α-CD) and phenylboronic acid (PBA)-terminated PEO crosslinker. Dynamic covalent bonds between PVA and PBA provide sugar-responsive crosslinking, and the inclusion complexation between PEO and α-CD can promote hydrogel formation and enhance hydrogel stability. The ratios of the three components have a remarkable effect on the gelation time and the mechanical properties of the final gels. In rheological measurements, the hydrogels are demonstrated to possess solid-like behaviour and good structural recovery ability after yielding. The sugar-responsiveness of the hydrogels was examined by protein loading and release experiments, and the results indicate that this property is also dependent on the compositions of the gels; at a proper component ratio, a new glucose-responsive hydrogel system operating at physiological pH can be obtained. The combination of good biocompatibility of the three components and the easy preparation of hydrogels with tunable glucose-responsiveness may enable an alternative design of hydrogel systems that finds potential applications in biomedical and pharmaceutical fields, such as treatment of diabetes.
Co-reporter:Xiao-Wei Kan;Xin-Xing Deng;Fu-Sheng Du
Macromolecular Chemistry and Physics 2014 Volume 215( Issue 22) pp:2221-2228
Publication Date(Web):
DOI:10.1002/macp.201400264
Co-reporter:Ran Ji, Jing Cheng, Ting Yang, Cheng−Cheng Song, Lei Li, Fu-Sheng Du, and Zi-Chen Li
Biomacromolecules 2014 Volume 15(Issue 10) pp:
Publication Date(Web):August 21, 2014
DOI:10.1021/bm500711c
We report a new type of pH-sensitive supramolecular aggregates which possess a programmable character of sequential dePEGylation and degradation. As a platform of designing and building multifunctional supramolecular nanoparticles, a family of 6-OH ortho ester-modified β-cyclodextrin (β-CD) derivatives have been synthesized via the facile reaction between β-CD and cyclic ketene acetals with different alkyl lengths. These asymmetric acid-labile β-CD derivatives formed amphiphilic supramolecules with adamantane-modified PEG through host–guest interaction in polar solvents such as ethanol. The supramolecules can self-assemble in water to form acid-labile supramolecular aggregates. The results of TEM and light scattering measurements demonstrate that the size and morphology of the aggregates are influenced by the alkyl or PEG length and the host–guest feed ratio. By carefully balancing the alkyl and PEG lengths and adjusting the host–guest ratio, well-dispersed vesicles (50–100 nm) or sphere-like nanoparticles (200–500 nm) were obtained. Zeta potential measurements reveal that these supramolecular aggregates are capable of being surface-functionalized via dynamic host–guest interaction. The supramolecular aggregates were stable at pH 8.4 for at least 12 h as proven by the 1H NMR and LLS measurements. However, rapid dePEGylation occurred at pH 7.4 due to the hydrolysis of the ortho ester linkages locating at the interface, which resulted in aggregation of the dePEGylated hydrophobic inner cores. Upon further decreasing the pH to 6.4, the hydrophobic cores were further degraded due to the acid-accelerated hydrolysis of the ortho esters. The incubation stability of the acid-labile supramolecular aggregates in neutral buffer could be improved by incorporating hydrophobic poly(ε-caprolactone) into the core of the aggregates.
Co-reporter:Lei Li, Xin-Xing Deng, Zi-Long Li, Fu-Sheng Du, and Zi-Chen Li
Macromolecules 2014 Volume 47(Issue 14) pp:4660-4667
Publication Date(Web):July 1, 2014
DOI:10.1021/ma501019c
We report the first example of realizing the multifunctionalization of photodegradable polymers for the preparation of reactive micropatterns. Three o-nitrobenzaldehyde monomers (M1, M2, and M3) with allyl, propargyl, and epoxy groups were synthesized in high yields by the simple reactions of 5-hydroxy-2-nitrobenzaldehyde with allyl bromide, propargyl bromide, and epichlorohydrin, respectively. Passerini multicomponent polymerization (Passerini MCP) of M1, M2, or M3 with 1,6-hexanedioic acid and 1,6-diisocyanohexane generated three poly(ester–amide)s (P1, P2, and P3), the ester linkages of which were o-nitrobenzyl derivatives with functional groups from the corresponding monomers. Therefore, these polymers are photodegradable and can also be further modified by efficient click reactions like thiol–ene, copper catalyzed azide–alkyne cycloaddition (CuAAC), and epoxy–amine reaction. Furthermore, Passerini MCP of M1, M2, and M3 with 1,6-hexanedioic acid and 1,6-diisocyanohexane could yield a photodegradable triply functional polymer (P4) containing all the three functional side groups which can be further modified by sequential click reactions. All the polymers were thoroughly characterized by 1H NMR and GPC. Degradation of the polymers in solution under UV irradiation was investigated by UV–vis and GPC, and they can all be photocleaved into oligomers and small molecules in 30 min. These functional polymers are extremely useful as positive photoresists to create reactive micropatterns. As an example, the triply functional polymer film was fabricated and cross-linked by epoxy–amine reaction. After photoirradiation under a mask, reactive patterns with allyl and propargyl groups were obtained. Sequential modification of the reactive sites by CuAAC and thiol–ene reactions afforded multifunctional patterned surfaces with tunable properties as confirmed by scanning electron micrograph (SEM) and confocal fluorescence microscopy.
Co-reporter:Zi-Long Li, An Lv, Fu-Sheng Du, and Zi-Chen Li
Macromolecules 2014 Volume 47(Issue 17) pp:5942-5951
Publication Date(Web):August 19, 2014
DOI:10.1021/ma5013732
We demonstrate that monomer sequence is important to regulate the vinyl copolymer thermal properties by intrachain cyclization. This is exemplified by the spontaneous intrachain cyclization with the formation of γ-butyrolactone by dihydroxylation of the internal alkenes of a designed periodic copolymer. A structurally symmetric α,ω-diene monomer 1 containing two tail-to-tail connected ethyl acrylate units was synthesized via a two-step approach. The acyclic diene metathesis (ADMET) polymerization of monomer 1 was conducted with a Hoveyda–Grubbs second generation catalyst in the presence of p-benzoquinone to get well-defined polymer (P1) with high molecular weights as revealed by GPC, NMR, and MALDI-TOF-MS characterizations. Dihydroxylation of P1 using hydrogen peroxide as the oxidant was successfully conducted to afford HP1. Characterization of HP1 by NMR and IR spectra indicated that it contained γ-butyrolactone units in the polymer main chain. Control experiments with four different polymers indicated that the formation of this ring structure was the outcome of the specific sequence of vinyl alcohol–ethyl acrylate formed by dihydroxylation of P1. The cyclization efficiency of P1 was calculated to be 77%. The Tgs of all the modified polymers were increased compared to those of the unsaturated samples; significantly, the Tg of HP1 was drastically elevated by 160 °C as compared to that of P1.
Co-reporter:An Lv, Zi-Long Li, Fu-Sheng Du, and Zi-Chen Li
Macromolecules 2014 Volume 47(Issue 22) pp:7707-7716
Publication Date(Web):November 14, 2014
DOI:10.1021/ma5020066
We report a facile strategy for the synthesis, functionalization, and controlled degradation of high molecular weight polyesters based on itaconic acid (IA) and 10-undecenol. A diene monomer, di(10-undecenyl) itaconate (DUI), was synthesized from IA and 10-undecenol by esterification reaction. The acyclic diene metathesis (ADMET) polymerization of DUI was conducted with Grubbs first-generation catalyst (G-I) to afford high molecular weight polyesters (PEIA: P1 and P2). Modification of P1 with three mercaptans (3-mercapto-1,2-propanediol (MP), benzyl mercaptan (BM), and dodecyl mercaptan (DM)) and piperidine (PI) via Michael addition reaction with the itaconate vinyl groups was performed. Quantitative postpolymerization modifications with no degradation of the polyesters were achieved for all the three mercaptans and PI as revealed by NMR and GPC characterizations. One-pot sequential modification of P1 with MP and PI was also successfully conducted. Thermal properties of the modified polyesters were studied by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). All the modified polyesters are semicrystalline with variable glass transition and melting temperatures which are affected by the modified side groups. Based on a detailed model reaction study, controlled modification of the itaconate vinyl groups with primary amines (sec-butylamine and 3-pentanamine) without intramolecular cyclization was achieved. Thus, sec-butylamine was used to modify P1 to generate a secondary amine functionalized polyester (P1-BA/DM) which was stable at low temperature but undergone self-degradation in solid or solution via intramolecular cyclization with the formation of a five-membered lactam at elevated temperatures. This is a new kind of self-degradable polyester with controllable degradation rates.
Co-reporter:Lei Li, An Lv, Xin-Xing Deng, Fu-Sheng Du and Zi-Chen Li
Chemical Communications 2013 vol. 49(Issue 76) pp:8549-8551
Publication Date(Web):30 Jul 2013
DOI:10.1039/C3CC44557G
Passerini three-component reaction and multicomponent polymerization (MCP) were demonstrated to be facile methods for the preparation of photo-cleavable polymers, photo- and redox-dually cleavable polymers, as well as block copolymers.
Co-reporter:Yao-Zong Wang, Xin-Xing Deng, Lei Li, Zi-Long Li, Fu-Sheng Du and Zi-Chen Li
Polymer Chemistry 2013 vol. 4(Issue 3) pp:444-448
Publication Date(Web):03 Dec 2012
DOI:10.1039/C2PY20927F
Polyamides with various functional side groups were synthesized via Passerini reaction in a one-pot approach. The polymerization conditions and kinetics as well as the resulting polymer structures were thoroughly investigated. The facile introduction of various pendant groups, especially alkynyl and alkenyl groups, provides a platform for efficient post-polymerization modification by click chemistry.
Co-reporter:Cheng-Cheng Song, Ran Ji, Fu-Sheng Du, De-Hai Liang, and Zi-Chen Li
ACS Macro Letters 2013 Volume 2(Issue 3) pp:273
Publication Date(Web):March 8, 2013
DOI:10.1021/mz4000392
We report a versatile method to tune the hydrolysis of the ortho ester-containing block copolymers by covalently incorporating oxidation-sensitive phenylboronic ester units. A series of block copolymers which contain a polyethylene glycol (PEG) block and a hydrophobic segment composed of different amounts of pendent ortho ester and phenylboronic ester groups were synthesized. These copolymers can self-assemble into narrowly dispersed micelle-like nanoparticles in phosphate buffer. The kinetics of phenylboronic ester oxidation and ortho ester hydrolysis in the nanoparticles were studied at different pH and H2O2 concentration. The results indicated that the phenylboronic ester oxidation rate was faster than the ortho ester hydrolysis rate at neutral pH, and both processes were accelerated with increasing H2O2 concentration. Nanoparticles which are extremely sensitive to the biorelevant concentration of H2O2 (50 μM) at pH 7.4 were obtained, suggesting great promise for inflammation-specific drug delivery.
Co-reporter:An Lv, Xin-Xing Deng, Lei Li, Zi-Long Li, Yao-Zong Wang, Fu-Sheng Du and Zi-Chen Li
Polymer Chemistry 2013 vol. 4(Issue 13) pp:3659-3662
Publication Date(Web):08 May 2013
DOI:10.1039/C3PY00382E
We report a facile method for the synthesis of multi-block copolymers consisting of poly(ethylene glycol) (PEG) and poly(ester–amide) segments with an ordered side group sequence via multicomponent polymerization based on the Passerini reaction (PR). The technique involves the polymer supported liquid-phase synthesis of three PEG diacid macromonomers (M1–M3) via stepwise PR with tert-butyl isocyanoacetate and a functional aldehyde followed by selective hydrolysis, and the final multicomponent polymerization of M1–M3 with phenylacetaldehyde and 1,6-diisocyanohexane.
Co-reporter:Zeng-Ying Qiao, Jing Cheng, Ran Ji, Fu-Sheng Du, De-Hai Liang, Shou-Ping Ji and Zi-Chen Li
RSC Advances 2013 vol. 3(Issue 46) pp:24345-24353
Publication Date(Web):07 Oct 2013
DOI:10.1039/C3RA42824A
A family of amphiphilic block copolymers with pendent ortho ester groups were synthesized by modifying the double hydrophilic block copolymer PEO114-b-PVA240 with 2-ethylidene-4-methyl-1,3-dioxolane (EMD) under mild conditions (30 °C). The degree of modification (DM) of the ortho ester groups can be tuned by simply varying the feed ratio of EMD to the hydroxyl groups in the PVA block. These block copolymers are stable in an anhydrous environment. Laser light scattering (LLS) and transmission electron microscopy (TEM) measurements revealed that in weakly basic aqueous buffer, these amphiphilic block copolymers self-assembled into aggregates with different size and morphology, ranging from solid-like spherical nanoparticles to polymersomes as the DM increased. The acid-triggered dissociation behaviour of the aggregates were studied by LLS, nile red (NR) fluorescence and TEM. The copolymer aggregates dissociated faster in a buffer with the lower pH; the dissociation rate of the aggregates became faster for the copolymers with lower DM. The polymersomes can load both hydrophilic biomacromolecules like lysozyme and hydrophobic anticancer drug doxorubicin (DOX). The drug-loaded polymersomes were stable in neutral phosphate buffer for at least 6 h with a payload leakage of less than 25% in 12 h at 37 °C; however, significant acid-triggered payload release was accomplished even at a mildly acidic pH (6.0). Finally, the DOX-loaded polymersomes exhibited a concentration-dependent toxicity to MCF-7 and HeLa cells while the copolymers themselves are non-toxic.
Co-reporter:Zeng-Ying Qiao, Ran Ji, Xiao-Nan Huang, Fu-Sheng Du, Rui Zhang, De-Hai Liang, and Zi-Chen Li
Biomacromolecules 2013 Volume 14(Issue 5) pp:
Publication Date(Web):April 9, 2013
DOI:10.1021/bm400180n
A series of well-defined thermoresponsive diblock copolymers (PEO45-b-PtNEAn, n = 22, 44, 63, 91, 172) were prepared by the atom transfer radical polymerization of trans-N-(2-ethoxy-1,3-dioxan-5-yl) acrylamide (tNEA) using a poly(ethylene oxide) (PEO45) macroinitiator. All copolymers are water-soluble at low temperature, but upon quickly heating to 37 °C, laser light scattering (LLS) and transmission electron microscopy (TEM) characterizations indicate that these copolymers self-assemble into aggregates with different morphologies depending on the chain length of PtNEA and the polymer concentration; the morphologies gradually evolved from spherical solid nanoparticles to a polymersome as the degree of polymerization (“n”) of PtNEA block increased from 22 to 172, with the formation of clusters with rod-like structure at the intermediate PtNEA length. Both the spherical nanoparticle and the polymersome are stable at physiological pH but susceptible to the mildly acidic medium. Acid-triggered hydrolysis behaviors of the aggregates were investigated by LLS, Nile red fluorescence, TEM, and 1H NMR spectroscopy. The results revealed that the spherical nanoparticles formed from PEO45-b-PtNEA44 dissociated faster than the polymersomes of PEO45-b-PtNEA172, and both aggregates showed an enhanced hydrolysis under acidic conditions. Both the spherical nanoparticle and polymersome are able to efficiently load the hydrophobic doxorubicin (DOX), and water-soluble fluorescein isothiocyanate-lysozyme (FITC-Lys) can be conveniently encapsulated into the polymersome without using any organic solvent. Moreover, FITC-Lys and DOX could be coloaded in the polymersome. The drugs loaded either in the polymersome or in the spherical nanoparticle could be released by acid triggering. Finally, the DOX-loaded assemblies display concentration-dependent cytotoxicity to HepG2 cells, while the copolymers themselves are nontoxic.
Co-reporter:Li-Jing Zhang, Xin-Xing Deng, Fu-Sheng Du, and Zi-Chen Li
Macromolecules 2013 Volume 46(Issue 24) pp:9554-9562
Publication Date(Web):December 12, 2013
DOI:10.1021/ma402191r
We report the synthesis, characterization, and degradation of a new type of functional poly(4-hydroxybutyrate) (P4HB). The polyesters were obtained via the Passerini multicomponent polymerization (MCP) of (E)-4-oxobut-2-enoic acid with two different isocyanides at room temperature and the subsequent hydrogenation. The trans-double bond in the monomer was designed to inhibit the formation of five-membered lactone and promote the polymerization. Two different side groups were incorporated into the side chains of the polyesters by varying the isocyanide component. All the polymers were thoroughly characterized by a variety of methods. Degradation of the polyester under acidic and neutral conditions was investigated by 1H NMR and GPC. In both cases head-to-tail degradation via intramolecular cyclization by the attack of the hydroxyl end group to the ester carbonyl moiety occurred and yielded a nonacidic γ-butyrolactone derivative as the single degradation product. On the basis of control experiments with small model compounds and other types of polyester, we proposed the degradation mechanism. In acidic condition, random scission of the ester group occurred simultaneously at a much slower rate than that of the head-to-tail degradation, while in neutral condition, random scission did not occur and the polymers degraded in a controllable unzipping depolymerization manner.
Co-reporter:Cheng-Cheng Song, Cui-Cui Su, Jing Cheng, Fu-Sheng Du, De-Hai Liang, and Zi-Chen Li
Macromolecules 2013 Volume 46(Issue 3) pp:1093-1100
Publication Date(Web):February 1, 2013
DOI:10.1021/ma301964n
We describe an efficient approach to modulate the hydrolysis of the ortho ester-containing polymers by incorporating different amount of tertiary amino (TA) groups. The block copolymers (NE0–NE3) contain a hydrophilic poly(ethylene glycol) (PEG) segment and hydrophobic chains constituted by random methacrylate copolymers with pendent acid-labile cyclic ortho ester and TA groups and were synthesized by a two-step approach. First, atom transfer radical copolymerization of 2-hydroxyethyl methacrylate and 2-(diethylamino)ethyl methacrylate using mPEG45-Br as a macroinitiator afforded the block copolymer precursors. Then, reaction of the precursors with 2-ethylidene-4-methyl-1,3-dioxolane transformed the pendent hydroxyl groups into cyclic ortho ester groups. The hydrophobic chains are similar in degree of polymerization, but the percent molar content of TA increases from 0% for NE0 to ∼15% for NE3. In phosphate buffer at pH 8.4, all the four amphiphilic block copolymers can self-assemble into stable nanoparticles with a monomodal distribution, which have a similar hydrophilic/hydrophobic balance as revealed by using pyrene and Nile red (NR) as fluorescent probes. Kinetic measurements of the ortho ester hydrolysis in the copolymer nanoparticles were studied at different pH values by 1H NMR spectroscopy, NR fluorescence probe, and light scattering. The results indicated that all the copolymer nanoparticles exhibit the pH-dependent hydrolysis behaviors with the half-life times ranging from hundreds of minutes at pH 5.4 to several days at neutral pH. More importantly, we found that the TA units have an amphoteric effect on the hydrolysis kinetics of the surrounding pendent ortho esters in acidic media. When compared with copolymer nanoparticles of NE0 with no TA unit, the NE1 nanoparticles with a small amount of TA unit hydrolyzed much slower, whereas a faster hydrolysis was observed for the NE3 nanoparticles containing a higher amount of TA unit.
Co-reporter:Lei Li;Xiao-Wei Kan;Xin-Xing Deng;Cheng-Cheng Song;Fu-Sheng Du
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 4) pp:865-873
Publication Date(Web):
DOI:10.1002/pola.26443
Abstract
In this article, we demonstrate the Passerini three-component reaction as a simple, effective method for the synthesis of polymers with double functional end groups, which are key precursors for the preparation of ABC miktoarm terpolymers. Thus, via the one-step Passerini reaction of monomethoxy poly(ethylene glycol)–propionaldehyde (PEG-CHO) with 2-bromo-2-methylpropionic acid and propargyl isocyanoacetamide, the PEG chain end was simultaneously functionalized with one atom transfer radical polymerization (ATRP) initiating site and one alkynyl group. The resulting PEG(-alkynyl)-Br was then used for the synthesis of three types of miktoarm ABC terpolymers via two approaches. First, we conducted ATRP of N-isopropylacrylamide (NIPAM), then click reaction with azido-terminated polystyrene (PS-N3) or poly(tert-butyl acrylate) (PtBA-N3) and obtained two ABC miktoarm terpolymers PEG(-b-PNIPAM)-b-PS and PEG(-b-PNIPAM)-b-PtBA. Alternatively, we conducted single electron transfer living radical polymerization of tBA and click reaction with PS-N3 simultaneously to give PEG(-b-PtBA)-b-PS. All the polymer precursors and miktoarm terpolymers have been characterized by 1H NMR, Fourier transform infrared, gel permeation chromatography, demonstrating that both approaches provided well-defined ABC miktoarm terpolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Co-reporter:Zi-Long Li;Lei Li;Xin-Xing Deng;An Lv;Chun-Hao Wang;Fu-Sheng Du
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 13) pp:2900-2909
Publication Date(Web):
DOI:10.1002/pola.26682
ABSTRACT
Copolymers of ethylene and ethyl acrylate have been widely used as commodity materials in many fields. In this article, a general synthetic strategy toward fine tuning the ethyl acrylate content and facile control over the monomer sequence regularity of this important type of copolymer via acyclic diene metathesis (ADMET) polymerization followed by hydrogenation is demonstrated. Three structurally symmetric diene monomers (M1–M3) were synthesized in good yields via a three-step synthetic approach; each of the monomers contains two tail-to-tail linked ethyl acrylate units connected to the terminal alkenes by a methylene spacer with specific length. ADMET homopolymerization of M1–M3 and copolymerization of these monomers with 1,9-decadiene were conducted, and after hydrogenation, a family of periodic and random copolymers of ethylene and ethyl acrylate were obtained. All the polymer samples were characterized by gel permeation chromatography and nuclear magnetic resonance, and the thermal properties of the saturated copolymers were investigated with thermal gravimetric analysis and differential scanning calorimetry. The glass transition and melting behaviors of this family of ethylene and ethyl acrylate copolymers were found to be dependent on the ethyl acrylate content and the primary structure regularity in copolymers. Copolymers with low ethyl acrylate content and periodic microstructures exhibited better crystallinity. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2900–2909
Co-reporter:Zi-long Li;Lei Li;Fu-sheng Du 李子臣
Chinese Journal of Polymer Science 2013 Volume 31( Issue 2) pp:355-362
Publication Date(Web):2013 February
DOI:10.1007/s10118-013-1227-6
Acyclic diene metathesis polymerization (ADMET) enables convenient transfer of sequential information of the designed monomers to the corresponding sequence-regulated copolymers. In this study, two structurally symmetric monomers, M1 and M2, were synthesized via atom transfer radical addition (ATRA) of diethyl meso-2,5-dibromohexanedioate with 1,5-hexadiene and 1,7-octadiene, respectively. Thus, sequenced segment of VB-EA-EA-VB (VB and EA represent vinyl bromide and ethyl acrylate, respectively) was incorporated into the ADMET diene monomers. ADMET polymerization of these two monomers with Grubbs first generation catalyst (Grubbs-I) was performed in CH2Cl2 at 40°C for 5 days under nitrogen purge. Effects of catalyst amount, monomer concentration and methanol precipitation on the Mp and PDI of polymers were investigated by GPC, and the structures of the formed polymers were characterized by NMR. Our results indicate that using 3.0 mol% of Grubbs-I to monomer can afford polymers with high Mp. Moreover, selective precipitation in methanol enables complete removal of low molecular weight components from the crude products. Meanwhile, M2 exhibits higher ADMET polymerization reactivity than M1 due to its capability of suppressing negative neighboring group effect.
Co-reporter:Cheng-Cheng Song, Ran Ji, Fu-Sheng Du, and Zi-Chen Li
Macromolecules 2013 Volume 46(Issue 21) pp:8416-8425
Publication Date(Web):October 18, 2013
DOI:10.1021/ma401656t
We report the synthesis of a new type of amphiphilic poly(amino ester)s which can be completely degraded in aqueous media via H2O2 oxidation. The polymers were prepared by the controlled Michael-type addition polymerization of a phenylboronic pinacol ester-containing diacrylate and N-aminoethylpiperazine, followed by postmodification with mPEG5K-succinimide ester. Upon oxidation, the side chain phenylboronic esters will be transformed into phenol groups which can trigger the sequential self-immolative process to degrade the polymer main chain. Meanwhile, the amino groups on the polymer main chain are capable of trapping the highly active quinone methides generated in situ during the oxidative degradation of the polymers. Based on the detailed oxidation kinetics and products of several model compounds, the H2O2-triggered degradation of nanoparticles of these copolymers was investigated by NMR spectroscopy, GPC, and Nile red fluorescence probe. The results demonstrate that the poly(amino ester) backbones were completely degraded by H2O2, resulting in the dissociation of nanoparticles. Oxidative degradation rates of the nanoparticles could be accelerated by increasing the concentration of H2O2, the PEGylation degree, or the pH of the buffer. Interestingly, the in situ formed quinone methides could be captured by secondary amines due to their higher nucleophilicity than H2O. Of potential importance, these amphiphilic oxidation-responsive copolymers are sensitive to stimulation of 200 μM H2O2; therefore, they may find application in the field of intelligent drug/gene delivery systems.
Co-reporter:Zi-Long Li, An Lv, Lei Li, Xin-Xing Deng, Li-Jing Zhang, Fu-Sheng Du, Zi-Chen Li
Polymer 2013 Volume 54(Issue 15) pp:3841-3849
Publication Date(Web):8 July 2013
DOI:10.1016/j.polymer.2013.05.037
Periodic copolymers of ethylene and vinyl alcohol (EVA) were synthesized via acyclic diene metathesis (ADMET) polymerization of a series of structurally symmetric α,ω-diene monomers that containing two vinyl acetate (VAc) units, followed by exhaustive hydrogenation and subsequent hydrolysis. This synthetic methodology provided a new type of EVA copolymer with defined sequence and ever highest VA content via ADMET. These polymer samples were characterized by gel permeation chromatography (GPC), NMR, and matrix-assisted laser desorption/ionization time-of-fight mass spectroscopy (MALDI-TOF-MS). Thermal properties of EVAc and EVA copolymers were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). EVAc copolymers exhibited two-stage decompositions on TGA traces and displayed a glass transition on DSC thermograms. Meanwhile, the EVA copolymers showed glass transition stages and sharp melting peaks on DSC thermograms, with the Tm values being comparable to that of high density polyethylene (HDPE).Figure optionsDownload full-size imageDownload as PowerPoint slide
Co-reporter:Jihan Zhou, Fuyou Ke, Yuqiong Xia, Jianbo Sun, Ning Xu, Zi-Chen Li, Dehai Liang
Polymer 2013 Volume 54(Issue 10) pp:2521-2527
Publication Date(Web):26 April 2013
DOI:10.1016/j.polymer.2013.03.024
The polyelectrolyte complexes formed by DNA and polycations have been widely used as non-viral vectors for gene delivery. The DNA complex prepared in aqueous solutions is usually controlled by kinetics. In this work, we demonstrated, by using salmon testes DNA (2000 bp), poly-(L-lysine) (PLL35), and poly(ethylene oxide)-b-Poly-(L-lysine) (PEO45-b-PLL35), that the DNA complexes formed in dimethylformamide (DMF) was milder than those formed in aqueous solutions. In DMF, no precipitation of DNA complex is observed even at the stoichiometric charge ratio. Taking advantage of the weak complexation and better solubility of complex in DMF, we premixed DNA and PLL at higher concentration in DMF, followed by quenching the mixture into a large amount of aqueous solution. This method alleviates the kinetic control to a large extent, and the complex obtained is smaller in size and lower in molar mass than those prepared solely in aqueous solution. The morphology of the complex, as studied by AFM, is also different.
Co-reporter:Xin-Xing Deng, Lei Li, Zi-Long Li, An Lv, Fu-Sheng Du, and Zi-Chen Li
ACS Macro Letters 2012 Volume 1(Issue 11) pp:1300
Publication Date(Web):October 19, 2012
DOI:10.1021/mz300456p
Multicomponent polymerization based on Passerini reaction is described. Room temperature polymerization of dicarboxyl acid, monoaldehyde, and diisocyanide leads to the formation of a new type of sequence regulated poly(ester-amide)s in an efficient one-pot process. The polymerization was confirmed to be a stepwise mechanism, and the resulting polymers were characterized and determined to be linear polymers with a sequence regulated backbone repeating unit of ester–ester–amide–amide. When functional aldehydes were used, functional side groups could be easily introduced at the same time, providing a simple way for further modification.
Co-reporter:Bo-Tao Dong, Zi-Long Li, Li-Jing Zhang, Fu-Sheng Du and Zi-Chen Li
Polymer Chemistry 2012 vol. 3(Issue 9) pp:2523-2530
Publication Date(Web):18 Jun 2012
DOI:10.1039/C2PY20319G
We report on the facile synthesis of a range of new linear functionalized polyesters by controlled atom transfer radical polyaddition reactions. One bis-styrenic type monomer, 1,2-bis(4-vinylbenzyloxy)ethane (AA), and two bis-methacrylate type ATRP initiators, 1,2-bis(2-bromoisobutyryloxy)ethane (BB) and bis[2-(2-bromoisobutyryloxy)ethyl]disulfide (BssB), were synthesized. The polymerizations of monomer AA with BB and BssB were carried out in anisole at 0 °C, using Cu/CuBr2 coupled with N,N-bis(2-pyridylmethyl)octylamine (BPMOA) as the catalyst. The polymerization kinetics were investigated and the polymers were characterized by GPC and NMR, both confirming the step-wise mechanism with the formation of the expected linear polyesters having pendent bromides. When BssB was used, additional disulfide groups were incorporated in the polyester main chain, imparting a tunable degradation mechanism to the polyester. Moreover, the pendent bromides on the polymers could serve as initiation sites or precursors to azides to prepare biodegradable graft copolymers. This has been proven by two examples, reactivating the pendent bromides at room temperature to initiate the ATRP of other methacrylates, and transforming these groups into azido-groups by substitution reaction followed by click chemistry with alkynyl-terminated polyethylene glycol.
Co-reporter:Hengjie Lai, Guangtao Chen, Peiyi Wu and Zichen Li
Soft Matter 2012 vol. 8(Issue 9) pp:2662-2670
Publication Date(Web):23 Jan 2012
DOI:10.1039/C2SM06779J
Poly(3-ethyl-N-vinyl-2-pyrrolidone) (C2PVP) is a new type of thermoresponsive polymer which exhibits phase separation in water above the lower critical solution temperature (LCST) at about 26 °C. The thermoresponsive mechanism of C2PVP during the heating–cooling cycle has been investigated by means of temperature-dependent FTIR in combination with a two-dimensional correlation (2Dcos) technique and density functional theory (DFT) calculations. Compared with a secondary-amide thermoresponsive polymer such as poly(N-isopropyl acrylamide) (PNIPAM), the unusual phenomenon of an asymmetrical-to-symmetrical transition of the CO peak shape is observed in the conventional IR spectra of tertiary-amide polymer C2PVP. 2Dcos results confirmed that two species of CO groups (CO⋯2D2O and CO⋯D2O) mainly coexist at the initial heating, and they change to the other two CO groups involving the free CO and CO⋯DOD⋯OC after heating, with the latter predominant above the LCST. A slight hysteresis is observed in the cooling process attributed to the existence of a weak “crosslinking” point originating from the structure of CO⋯DOD⋯OC. Based on 2Dcos results, the dehydration process of different groups could be described in the following order: ethyl groups > CO groups > CH2 groups in ring (“>” means prior to), and the reversible sequence is observed during hydration process. In PNIPAM system, CH2 groups usually change prior to CO groups, while for C2PVP the dehydrated rate of CH2 groups (in ring) lags behind that of CO groups because of the steric hindrance of pyrrolidone structures. It is worth noting that cononsolvency of C2PVP can be found in water/methanol mixed solvents. The LCST of C2PVP in water/methanol mixture shifts from 29.5 to 16 °C as the methanol volume fraction reaches 50% and the phase separation totally disappears when the content of methanol is higher than 60%.
Co-reporter:Jing Cheng, Ran Ji, Shi-Juan Gao, Fu-Sheng Du, and Zi-Chen Li
Biomacromolecules 2012 Volume 13(Issue 1) pp:
Publication Date(Web):December 16, 2011
DOI:10.1021/bm201410c
This work presents a facile approach for preparation of acid-labile and biocompatible polymers with pendent cyclic ortho esters, which is based on the efficient and mild reactions between cyclic ketene acetal (CKA) and hydroxyl groups. Three CKAs, 2-ethylidene-1,3-dioxane (EDO), 2-ethylidene-1,3-dioxolane (EDL), and 2-ethylidene-4- methyl-1,3-dioxolane (EMD) were prepared from the corresponding cyclic vinyl acetals by catalytic isomerization of the double bond. The reaction of CKAs with different alcohols and diols was examined using trace of p-toluenesulfonic acid as a catalyst. For the monohydroxyl alcohols, cyclic ortho esters were formed by simple addition of the hydroxyl group toward CKAs with ethanol showing a much greater reactivity than iso-propanol. When 1,2- or 1,3-diols were used to react with the CKAs, we observed the isomerized cyclic ortho esters besides the simple addition products. Biocompatible polyols, that is, poly(2-hydroxyethyl acrylate) (PHEA) and poly(vinyl alcohol) (PVA) were then modified with CKAs, and the degree of substitution of the pendent ortho esters can be easily tuned by changing feed ratio. Both the small molecule ortho esters and the CKA-modified polymers demonstrate the pH-dependent hydrolysis profiles, which depend also on the chemical structure of the ortho esters as well as the polymer hydrophobicity.
Co-reporter:Zi-Long Li, Lei Li, Xin-Xing Deng, Li-Jing Zhang, Bo-Tao Dong, Fu-Sheng Du, and Zi-Chen Li
Macromolecules 2012 Volume 45(Issue 11) pp:4590-4598
Publication Date(Web):May 25, 2012
DOI:10.1021/ma3003483
The synthesis of a new family of periodic copolymers containing γ-butyrolactones by acyclic diene metathesis polymerization (ADMET) and their thermal properties are presented. Two symmetric diene monomers, M6 and M8, were designed. Both monomers contain two γ-butyrolactone units, but they are different in the length of methylene spacers between cyclic structures and terminal alkenes. The monomers have been prepared by a two-step approach; first, the atom transfer radical addition (ATRA) of diethyl meso-2,5-diiodohexanedioate with either 1,5-hexadiene or 1,7-octadiene was conducted to yield intermediates containing two γ-iodo ester sequences; subsequently, the specific sequence was transformed into γ-butyrolactone unit via intramolecular cyclization upon heating. The two monomers were polymerized using two Grubbs catalysts (Grubbs I and Grubbs II) to produce four polymers with moderate to high molecular weights (P6-1, P6-2, P8-1, and P8-2) and hydrogenation of which gave the final saturated polymers. The expected periodic copolymers have been obtained and were characterized with a variety of methods, indicating that the γ-butyrolactone units could endure the polymerization and hydrogenation. Polymers catalyzed by Grubbs II catalyst suffer from chain heterogeneity due to severe olefin isomerization. Thermal properties of the polymers were investigated via thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA measurements show that these polymers are stable up to 350 °C. DSC results demonstrate that the glass transition and melting behaviors of the polymers are not only affected by the rigidity of γ-butyrolactone units in polyethylene chains but also dependent on the methylene spacer length and chain homogeneity. Copolymerization of M6 or M8 with 1,9-decadiene resulted in random copolymers with lower γ-butyrolactone content and less regular chain structure. These copolymers exhibit lower Tg or Tm compared with the periodic copolymers.
Co-reporter:Rui Zhang;Yang Wang;Fu-Sheng Du;Ying-Li Wang;Ying-Xia Tan;Shou-Ping Ji
Macromolecular Bioscience 2011 Volume 11( Issue 10) pp:1393-1406
Publication Date(Web):
DOI:10.1002/mabi.201100094
Co-reporter:Jihan Zhou, Fuyou Ke, Yin-yin Tong, Zi-chen Li and Dehai Liang
Soft Matter 2011 vol. 7(Issue 21) pp:9956-9961
Publication Date(Web):30 Aug 2011
DOI:10.1039/C1SM05963G
Block copolymers containg poly(ethylene oxide) (PEO) have been widely used in biomedical applications. The PEO block is generally treated as the hydrophilic moiety. In this work, we demonstrated that PEO could serve as the “hydrophobic” block under certain conditions by using PEO-b-poly(vinyl alcohol) (PEO-b-PVA) as the example. Water is a non-selective solvent for both of the blocks, however, the addition of NaCl decreases the solubility of PEO in aqueous solution while it shows no effect on the PVA block. With the solubility of PEO being deteriorated by adding NaCl, PEO-b-PVA exhibited amphiphilic feature in aqueous solution with PEO being the “hydrophobic” block. Therefore, by just adding salts, uniform gel-like particles were formed by PEO-b-PVA of proper block ratio. These solid particles formed by dual hydrophilic copolymers with excellent biocompability may have great potential in biomedical applications.
Co-reporter:Xuyan Yang, Yin-Yin Tong, Zi-Chen Li and Dehai Liang
Soft Matter 2011 vol. 7(Issue 3) pp:978-985
Publication Date(Web):06 Dec 2010
DOI:10.1039/C0SM00257G
Using poly(vinyl alcohol)-b-poly(N-isopropylacrylamide) (PVA-b-PNIPAm) as an example, we demonstrate the concept of aggregation-induced gelation of PVA in dilute solution. PVA-b-PNIPAm forms aggregates in dilute solution at temperature above the transition point of PNIPAm, which significantly increases the local concentration of PVA chains. Therefore, PVA chains have a better chance to crystallize or to generate small crystalline nuclei, which function as cross-linkers in the later stages. When the solution is cooled to room temperature, PVA-b-PNIPAm gradually forms microgels at the time scale of days. We further investigated the effects of block ratio, heating rate, and urea concentration on the gelation process. It is found that larger PVA ratio, longer aging time and less urea content facilitated the gel formation. Rheological measurement at semidilute concentration also confirms gel formation after the heating/cooling treatment. The aggregation-induced gelation offers a new approach to prepare PVA gels without the introduction of toxic chemical cross-linkers.
Co-reporter:Yang Wang, Rui Zhang, Ning Xu, Fu-Sheng Du, Ying-Li Wang, Ying-Xia Tan, Shou-Ping Ji, De-Hai Liang, and Zi-Chen Li
Biomacromolecules 2011 Volume 12(Issue 1) pp:
Publication Date(Web):December 2, 2010
DOI:10.1021/bm101005j
Linear reduction-degradable cationic polymers with different secondary amine densities (S2 and S3) and their nonreducible counterparts (C2 and C3) were synthesized by Cu(I)-catalyzed azide−alkyne cycloaddition (CuAAC) step-growth polymerization of the dialkyne-oligoamine monomers and the diazide monomers. These polymers were studied with a goal of developing a set of new gene carriers. The buffering capacity and DNA binding ability of these polymers were evaluated by acid−base titration, gel retardation, and ethidium bromide (EB) exclusion assay. The polymers with lower amine density exhibit a weaker DNA-binding ability but a stronger buffering capacity in the range of pH 5.1 and 7.4. Particle size and zeta-potential measurements demonstrate that the polymers with higher amine density condense pDNA to form polyplexes with smaller sizes, while the disulfide bond in the backbone shows a negative effect on the condensing capability of the polymers, resulting in the formation of polyplexes with large size and nearly neutral surface. The reduction-sensitive polyplexes formed by polymer S2 or S3 can be disrupted by dithiothreitol (DTT) to release free DNA, which has been proven by the combination of gel retardation, EB exclusion assay, particles sizing, and zeta potential measurements. Cell viability measurements by MTT assay demonstrate that the reduction-degradable polymers (S2 and S3) have little cytotoxicity while the nonreducible polymers (C2 and C3) show obvious cytotoxicity, in particular, at high N/P ratios. In vitro transfection efficiencies of these polymers were evaluated using EGFP and luciferase plasmids as the reporter genes. Polymers S3 and S2 show much higher efficiencies than the nonreducible polymers C3 and C2 in the absence of 10% serum; unexpectedly, the lowest transfection efficiency has been observed for polymer S3 in the presence of serum.
Co-reporter:Rui Wang, Gunag-Tao Chen, Fu-Sheng Du, Zi-Chen Li
Colloids and Surfaces B: Biointerfaces 2011 Volume 85(Issue 1) pp:56-62
Publication Date(Web):15 June 2011
DOI:10.1016/j.colsurfb.2010.11.012
Amphiphilic diblock copolymers composed of poly(ethylene glycol) (PEG) and poly(l-leucine) (PLeu) with mannose at the chain end of PEG were synthesized by a combination of ring-opening polymerization (ROP) and click chemistry. First, an α-azido, ω-amino PEG (N3-PEG-NH2) was synthesized and converted to the corresponding amine hydrochloride (N3-PEG-NH2·HCl), which was used as a macroinitiator to initiate the ROP of l-leucine-N-carboxyanhydride (Leu-NCA), yielding three amphiphilic block copolymers with different chain lengths of PLeu (N3-PEG-b-PLeu). Then, click chemistry of the alkynyl mannose with N3-PEG-b-PLeu anchored a mannose moiety to the PEG chain end of the copolymer. The self-assembly behavior of these copolymers in water was investigated using transmission electron microscopy (TEM), laser light scattering (LLS) and circular dichroism (CD). Depending on the copolymer composition and the initial concentration of the copolymer in organic solvent, different morphologies (e.g. spherical micelle, wormlike micelle) were observed. The aggregation behavior was demonstrated to be controlled by secondary structure formation and the hydrophobic interactions of the PLeu segments. With mannose moieties on the surface of the aggregates, these aggregates could bind reversibly the lectin Concanavalin A (Con A).Graphical abstractResearch highlights▶ Three amphiphilic block copolymers with different chain lengths of PLeu and a mannose end group were prepared (M-PEG-b-PLeu). ▶ They formed different self-assembled structures in water depending on the chain length of PLeu. ▶ The formed nanoparticles were covered with mannose which show reversible binding with certain protein.
Co-reporter:Rui Wang, Ning Xu, Fu-Sheng Du and Zi-Chen Li
Chemical Communications 2010 vol. 46(Issue 22) pp:3902-3904
Publication Date(Web):21 Apr 2010
DOI:10.1039/C002473B
A mannose-modified polylysine was synthesized, the self-assembly of which in aqueous solution led to the formation of spherical micelles, vesicles and rod-like micelles in a controlled manner by simply changing the solution pH and adding a surfactant to the solution.
Co-reporter:Ning Yan, Jiaguang Zhang, Yuan Yuan, Guang-Tao Chen, Paul. J. Dyson, Zi-Chen Li and Yuan Kou
Chemical Communications 2010 vol. 46(Issue 10) pp:1631-1633
Publication Date(Web):03 Feb 2010
DOI:10.1039/B923290G
Two thermoresponsive polymers based on alkyl modified poly-vinylpyrrolidone (PVP) that exhibit very sensitive and reversible temperature-dependant water solubility are described. The application of these polymers as Au nanocatalyst stabilizers leads to a “smart” thermoresponsive Au nanoparticlecatalyst.
Co-reporter:Ying Zhao, Jing Zhao, Yun Yan, Zichen Li and Jianbin Huang
Soft Matter 2010 vol. 6(Issue 14) pp:3282-3288
Publication Date(Web):25 May 2010
DOI:10.1039/C002541K
The self-assembly and molecular packing mode of a novel, unsymmetrical bolaamphiphile, sodium 4-(6-hydroxyhexyloxy) cinnamate (SHHC) was studied. Tube-like structures were obtained in SHHC aqueous solution at pH 9.2. Upon UV irradiation, the SHHC molecules in the system were found to undergo four-center-type photocyclodimerization and photoisomerization. The combination of IR, XRD and Zeta potential results suggested the formation of a tail-to-tail type bilayer membrane structure: the SHHC molecules stretched upright with the cinnamate headgroups toward the outside in each layer, whereas the tail OH groups of two layers remained inside and formed interlayer hydrogen bonds. This parallel packing mode of SHHC molecules in the membrane was also confirmed by the pH-induced self-assembly transition. With increasing pH from 9.2 to 12.0, the low-curvatured tubes transformed into spherical vesicles, which was in line with the increased outer leaflet head group area as increasing pH. Our results demonstrated that upon careful molecular design, the orientation of unsymmetrical bolaamphiphiles can be controlled; π–π interactions between cinnamoyl groups were found to be strong enough to drive the formation of well-oriented molecular assemblies.
Co-reporter:Fu-Sheng Du, Yang Wang, Rui Zhang and Zi-Chen Li
Soft Matter 2010 vol. 6(Issue 5) pp:835-848
Publication Date(Web):22 Dec 2009
DOI:10.1039/B915020J
Despite significant advances in the past two decades, gene therapy is still in the stage of clinical trials worldwide mainly due to the lack of safe and efficient delivery vehicles for therapeutic nucleic acids. Among the various attempts to develop clinically applicable gene therapy, polymer-based nucleic acid delivery systems have attracted great interest, especially for the exciting RNAi-based gene therapy. Regarding in vivo nucleic acid delivery, in particular via intravenous injection, there are many extra- and intracellular obstacles, some of which are conflicting. Virus-mimicking nucleic acid delivery systems that combine multiple and programmable functions are thought to be very promising for conquering these challenging barriers. In this review article, we highlight recent progress in stimuli-responsive polymers that have been applied in fabrication of non-viral multi-functional nucleic acid vehicles, which are categorized by the type of stimulus: reduction potential, pH, temperature, and others. In each section, intelligent pDNA delivery systems are introduced first, followed by summarizing various responsive polymer-based siRNA vehicles. Considering the great potential of RNAi-based gene therapy, we devote some space to the recent progress of multi-functional siRNA delivery systems. In addition, different requirements in designing polymer-based siRNA and pDNA carriers are also specified in this review.
Co-reporter:Fu-Sheng Du, Xiao-Nan Huang, Guang-Tao Chen, Shrong-Shi Lin, Dehai Liang and Zi-Chen Li
Macromolecules 2010 Volume 43(Issue 5) pp:2474-2483
Publication Date(Web):February 4, 2010
DOI:10.1021/ma902227g
A series of poly(meth)acrylamide derivatives with pendent six-member cyclic orthoester groups, i.e., poly(N-(2-alkyloxy-1,3-dioxan-5-yl)methacrylamide)s and poly(N-(2-alkyloxy-1,3-dioxan-5-yl)acrylamide)s, have been synthesized and characterized. The difference between these polymers lies in the type of alkyl substitutes (R3), the stereochemical structures of the pendent cyclic orthoester groups (trans vs cis), and the main chain structures (polymethacrylamide vs polyacrylamide). Aqueous solution properties and pH-dependent hydrolysis behaviors of these polymers were studied by various methods including turbidimetry, fluorescence probe, DSC, 1H NMR, microscopy, and light scattering. The results show that these polymers except PtNPM can be dissolved in water at low temperature, and all of the water-soluble polymers are thermosensitive with different lower critical solution temperatures (LCSTs) and susceptible to hydrolysis in mildly acidic conditions. Both thermosensitive properties and acid-triggered hydrolysis behaviors of the polymers are closely related to the polymer structures. In general, polymethacrylamides display higher cloud points (CPs) than polyacrylamides. In addition, the polymers with larger R3 and trans configuration have a lower CP and greater magnitude of dehydration and exhibit a liquid−solid phase transition, while those with smaller R3 and cis configuration have a smaller magnitude of dehydration and undergo a liquid−liquid phase separation. In addition, a two-stage transition process is observed for the polymers with R3 being methyl. 1H NMR results reveal that the acid-triggered hydrolysis rate of the pendent orthoesters increases as R3 changed from methyl to isopropyl, and the configuration changed from cis to trans. The synergetic effect of R3 and stereochemical structure of the pendent groups on the hydrolysis products of the polymers were also observed
Co-reporter:Lin Deng, Chunhao Wang, Zi-Chen Li and Dehai Liang
Macromolecules 2010 Volume 43(Issue 6) pp:3004-3010
Publication Date(Web):February 17, 2010
DOI:10.1021/ma902601d
Using poly(acrylic acid) (PAA) and polyacrylamide (PAAm) as an example, we studied the mechanism of hydrogen-bonding complexation in dilute solution by both static and dynamic light scattering. In 20 mM phosphate buffer at pH = 3, the condition suitable for complexation of PAA and PAAm, neither PAA nor PAAm stayed as individual polymer chains at 8.0 mg/mL. Instead, most of PAA formed “multimacroion clusters” (or slow mode) due to the negative charges, and a small portion of PAAm formed associates mainly via hydrogen bonds. After PAA and PAAm solutions were mixed at stoichiometric ratio at room temperature, the slow mode, with PAA being dominant, persisted. The hydrogen-bonding complexation induced by cooling was evolved from the slow mode rather than from the single PAA or PAAm chains. Therefore, at the temperature where phase separation occurred, a fairly large amount of free PAAm chains still existed in the system. Our study demonstrated that the growth of the hydrogen-bonding complex, as well as the optimal ratio for complex, was highly dependent on the status of the component polymers before complexation.
Co-reporter:Bo-Tao Dong, Yong-Quan Dong, Fu-Sheng Du, and Zi-Chen Li
Macromolecules 2010 Volume 43(Issue 21) pp:8790-8798
Publication Date(Web):October 7, 2010
DOI:10.1021/ma101807y
A new unsymmetrical AB* inimer, p-(2-bromoisobutyloylmethyl)styrene (BiBMS), was applied to the atom transfer radical polymerization (ATRP) to prepare a family of polymers with the topologies ranging from linear to branched. The catalyst system was Cu/CuBr2 coupled with 2,2′-bipyridine (Bipy) or N,N-bis(2-pyridylmethyl)octylamine (BPMOA) as a ligand in toluene or anisole at different temperatures, which ensured a very low catalyst (CuBr) concentration throughout the polymerization by a slow reduction process. First, BiBMS was polymerized in anisole at 0 °C using Cu/CuBr2/BPMOA as a catalyst system; at this temperature, the initiating activity of the formed A* was frozen and the polymerization was a step-growth polymerization, resulting in the formation of a linear polymer (LP1) whose main chain was linked by ester bonds. Second, BiBMS was polymerized in toluene at 20 °C using Cu/CuBr2/Bipy as a catalyst system. Under this condition, initiation from the B* of BiBMS was slow, followed by a fast radical polymerization of the BiBMS vinyl bonds and a slow deactivation, thereby affording another linear polymer (LP2), the structure of which was the same as that obtained by common free radical polymerization of BiBMS except the end groups. The conversion of BiBMS was controlled to be moderate to suppress the possible initiation from the pendant B* along the polymer main chain. Third, BiBMS was polymerized in anisole at various temperatures using Cu/CuBr2/Bipy as a catalyst system; three branched polymers (BP1, BP2, BP3) with different degree of branching (DB) were obtained, the DB of which could be easily adjusted by changing temperature (BP1, DB = 0.12 at 20 °C; BP2, DB = 0.26 at 40 °C; BP3, DB = 0.37 at 60 °C).
Co-reporter:Zeng-Ying Qiao, Fu-Sheng Du, Rui Zhang, De-Hai Liang and Zi-Chen Li
Macromolecules 2010 Volume 43(Issue 15) pp:6485-6494
Publication Date(Web):July 16, 2010
DOI:10.1021/ma101090g
Two acrylate monomers with six-member cyclic ortho ester groups, i.e., 2-(1,3-dioxan-2-yloxy)ethyl acrylate (DEA) and 2-(5,5-dimethyl-1,3-dioxan-2-yloxy) ethyl acrylate (DMDEA), were synthesized. These two monomers were copolymerized with an oligo(ethylene glycol) acrylate (OEGA) under atom transfer radical polymerization conditions to afford two series of thermoresponsive copolymers, poly(DEA-co-OEGA)s and poly(DMDEA-co-OEGA)s. All the copolymers were soluble in water to form transparent solutions at low temperature, however, some of them exhibited association behaviors below the cloud point (CP) as evidenced by 1H NMR, dynamic light scattering (DLS) and fluorescence method. The aggregation tendency of the copolymers depends on their composition as well as the structure of the ortho ester units. With a similar composition, poly(DMDEA-co-OEGA) showed a stronger aggregation tendency than poly(DEA-co-OEGA). In addition, increasing molar content of the ortho ester units in a copolymer promoted its aggregation in water. Thermally induced phase transitions of these copolymers were studied by various methods including turbidimetry, temperature-dependent 1H NMR, DLS, and microscopy. The results indicate that CP of the copolymers increased with increasing the content of OEGA units, but the changing behaviors of CP were rather different for two types of copolymers, which can be ascribed to the difference in hydrophobicity of the ortho ester units. Little hysteresis was observed for the copolymers with more OEGA units while those with more ortho ester units showed significant hysteresis probably due to the hydrophobic character of the ortho ester. The formation of coacervate droplets above CP reveals that the copolymers underwent a liquid−liquid phase separation upon heating. pH-dependent hydrolyses of the copolymers were studied by turbidimetry and 1H NMR methods. The hydrolysis rate depends greatly on pH and the hydrophilic/hydrophobic balance of the copolymers: lower pH and more hydrophilic character resulted in a faster hydrolysis rate. Finally, this type of acid-labile thermoresponsive copolymers and the acid-catalyzed hydrolysis products have low cytotoxicity.
Co-reporter:Nan Hu;Wen-Xi Ji;Yin-Yin Tong;Er-Qiang Chen
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 20) pp:4621-4626
Publication Date(Web):
DOI:10.1002/pola.24195
Abstract
The reversible addition-fragmentation chain transfer (RAFT) polymerization of N-vinylcarbazole (NVK) mediated by macromolecular xanthates was used to prepare three types of block copolymers containing poly(N-vinylcarbazole) (PVK). Using a poly(ethylene glycol) monomethyl ether based xanthate (PEG-X), the RAFT polymerization of NVK proceeded in a controlled way to afford a series of PEG-b-PVK with different PVK chain lengths. Successive RAFT polymerization of NVK and vinyl acetate (VAc) with a small molecule xanthate (X1) as the chain transfer agent was tested to prepare PVK-b-PVAc. Though both monomers can be homopolymerized in a controlled manner with this xanthate, only by polymerizing NVK first could give well-defined block copolymers. The xanthate groups in the end of PVK could be removed by radical-induced reduction using tributylstannane, and PVK-b-PVA was obtained by further hydrolysis of PVK-b-PVAc under basic conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Co-reporter:Guang-Tao Chen, Chun-Hao Wang, Jia-Guang Zhang, Yang Wang, Rui Zhang, Fu-Sheng Du, Ning Yan, Yuan Kou, and Zi-Chen Li
Macromolecules 2010 Volume 43(Issue 23) pp:9972-9981
Publication Date(Web):November 8, 2010
DOI:10.1021/ma101636m
A series of new monomers with different substituents at the 3-position of N-vinyl-2-pyrrolidone (NVP) were synthesized. The substituents include simple alkyl (methyl, ethyl, propyl, and isopropyl), ether (methoxy ethyl and ethoxy ethyl), and functional groups (e.g., aldehyde, epoxy, and acetylene). These monomers were (co)polymerized radically to produce a family of (co)polymers based on poly(N-vinyl-2-pyrrolidone) (PVP), and the copolymer compositions could be controlled through varying comonomer feed ratio. When the monomers are substituted with ethyl-, methyl-, or ether-containing alkyl chains, their homopolymers are soluble in cold water but display sensitive and reversible phase transition upon heating to a cloud point temperature (CP). Control over CP of homopolymers was achieved by changing the hydrophilicity of the substituents. CP could also be tuned by copolymerization of different monomers or adding NaCl to the polymer aqueous solution. The mechanism of the thermoresponsive properties was studied by temperature-dependent 1H NMR and microcalorimetry. The results confirmed that the phase transitions of (co)polymers bearing ether substituents were less cooperative with lower phase transition enthalpy and less dehydration even at temperatures well above the CP, and the transition is predominately liquid to liquid. In addition, aldehyde, epoxy, and acetylene groups were introduced to the (co)polymer chains as reactive groups; model reactions of these groups with other molecules were very efficient and simple. Thus, these polymers can subsequently be modified to impart additional functionality to be used as thermoresponsive polymers for bioconjugation. Finally, these polymers are demonstrated to be at least as biocompatible as PVP.
Co-reporter:Chao Zhang, Shijuan Gao, Wei Jiang, Song Lin, Fusheng Du, Zichen Li, Wenlin Huang
Biomaterials 2010 31(23) pp: 6075-6086
Publication Date(Web):
DOI:10.1016/j.biomaterials.2010.04.042
Co-reporter:Yong-Quan Dong, Bo-Tao Dong, Fu-Sheng Du, Jian-Qiang Meng, Zi-Chen Li
Polymer 2009 50(1) pp: 125-132
Publication Date(Web):
DOI:10.1016/j.polymer.2008.10.046
Co-reporter:Yin-Yin Tong;Yong-Quan Dong;Fu-Sheng Du
Journal of Polymer Science Part A: Polymer Chemistry 2009 Volume 47( Issue 7) pp:1901-1910
Publication Date(Web):
DOI:10.1002/pola.23288
Abstract
A methodology for the synthesis of well-defined poly(ethylene oxide)-block-poly(vinyl alcohol) (PEO-b-PVA) and PVA-b-PEO-b-PVA polymers was reported. Novel xanthate end-functionalized PEOs were synthesized by a series of end-group transformations. They were then used to mediate the reversible addition–fragmentation chain transfer polymerization of vinyl acetate to obtain well-defined poly(ethylene oxide)-b-poly(vinyl acetate) (PEO-b-PVAc) and PVAc-b-PEO-b-PVAc. When these block copolymers were directly hydrolyzed in methanol solution of sodium hydroxide, polymers with brown color were obtained, which was due to the formation of conjugated unsaturated aldehyde structures. To circumvent these side reactions, the xanthate groups were removed by adding a primary amine before hydrolysis and the products thus obtained were white powders. The polymers were characterized by gel permeation chromatography, 1H NMR spectroscopy and FT-IR. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1901–1910, 2009
Co-reporter:Yin-Yin Tong;Rui Wang;Ning Xu;Fu-Sheng Du
Journal of Polymer Science Part A: Polymer Chemistry 2009 Volume 47( Issue 18) pp:4494-4504
Publication Date(Web):
DOI:10.1002/pola.23502
Abstract
A new azide-functionalized xanthate, S-(4-azidomethylbenzyl) O-(2-methoxyethyl) xanthate, was synthesized and used to mediate the reversible addition fragmentation chain transfer polymerization of vinyl acetate. The polymerization was demonstrated to be controlled, and well-defined PVAc with α-azide, ω-xanthate groups were obtained, the xanthate groups of which were further removed by radical-induced reduction with lauroyl peroxide in the presence of excess 2-propanol. Hydrolysis of α-azide-terminated PVAc (N3-PVAc) led to the formation of the corresponding α-azide-terminated PVA (N3-PVA). Finally, end-modification of N3-PVA by click chemistry with alkyne-end-capped poly(caprolactone) (A-PCL), alkynyl-mannose, and alkynyl-pyrene was carried out to obtain a new block copolymer PCL-b-PVA, and two PVA with mannose or pyrene as the end functional groups. The polymers were characterized by gel permeation chromatography, 1H NMR spectroscopy, and FTIR. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4494–4504, 2009
Co-reporter:Xiaonan Huang, Fusheng Du, Jing Cheng, Yongquan Dong, Dehai Liang, Shouping Ji, Shrong-Shi Lin and Zichen Li
Macromolecules 2009 Volume 42(Issue 3) pp:783-790
Publication Date(Web):January 16, 2009
DOI:10.1021/ma802138r
An orthoester-containing monomer, trans-N-(2-ethoxy-1,3-dioxan-5-yl)acrylamide (tNEA), was synthesized. Atom transfer radical polymerization of tNEA using a poly(ethylene glycol) (PEG) macroinitiator afforded three acid-labile thermoresponsive block copolymers: PEG-b-PtNEA27, PEG-b-PtNEA56, and PEG-b-PtNEA73. These block copolymers are water-soluble at low temperatures (<13 °C). Thermally induced phase transition behaviors, including the critical aggregation temperatures (CATs), of these polymers were investigated by light scattering and 1H NMR. The results indicated that the longer the PtNEA chain length, the lower the CAT. Upon heating above the CATs, all the three polymers underwent a phase transition and formed polymeric micelles or micelle-like nanoparticles with PEG as the shell and PtNEA block as the core. Both the sizes and morphologies of the micelles were found to be affected by the heating rate and the salt concentration in the buffers. The micelles, formed through a fast heating procedure in the buffer with a relatively high salt concentration, have a smaller size and a more compacted structure. pH-dependent destabilization of the polymeric micelles prepared from PEG-b-PtNEA73 was studied by using light scattering and Nile Red fluorescence. The results demonstrated that hydrophobic Nile Red could be loaded in the micelles that were stable at pH 7.4, but destabilized in mildly acidic media. The dissociation of the micelles and the subsequent release of Nile Red were induced by the acid-triggered hydrolysis of the orthoester groups, which was proved by the 1H NMR spectra.
Co-reporter:Yong-Quan Dong, Yin-Yin Tong, Bo-Tao Dong, Fu-Sheng Du and Zi-Chen Li
Macromolecules 2009 Volume 42(Issue 8) pp:2940-2948
Publication Date(Web):March 19, 2009
DOI:10.1021/ma802361h
Amphiphilic tadpole-shaped copolymers consisting of a polystyrene (PS) ring and a poly(ethylene oxide) (PEO) tail were synthesized via atom transfer radical polymerization (ATRP) and click chemistry. First, PEO with a propargyl group and an ATRP initiating group was prepared via click chemistry and esterification. Then, a diblock copolymer, PEO-b-PS, which contained a propargyl group at the junction point and an azide group at the PS chain end, was prepared via ATRP of styrene, followed by transformation of the PS bromo end to an azide group. Finally, cyclization of the PS segment via click chemistry in dilute solution led to the formation of cyclic PS-b-linear PEO (c-PS-b-PEO). Because both the chain length of PEO and the ring size of cyclic PS can be easily tuned, a series of c-PS-b-PEOs was prepared. All of the polymers were characterized with gel permeation chromatography, NMR spectroscopy, FTIR, and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS). c-PS-b-PEOs showed smaller hydrodynamic volumes compared with their linear precursors. Self-assembly of one c-PS-b-PEO sample and its linear precursor in water was preliminarily investigated by transmission electron microscopy. We found that vesicles were the main morphologies for both polymers, but they were different in size; those from c-PS-b-PEO were much larger.
Co-reporter:Yin-Yin Tong, Yong-Quan Dong, Fu-Sheng Du and Zi-Chen Li
Macromolecules 2008 Volume 41(Issue 20) pp:7339-7346
Publication Date(Web):September 27, 2008
DOI:10.1021/ma800799x
The synthesis of well-defined poly(vinyl acetate)-b-polystyrene (PVAc-b-PSt) by combination of atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization was described. Two difunctional compounds, S-(2-chloropropionoxyethoxycarbonylmethyl) O-ethyl xanthate (2) and S-(2-bromo-2-methylpropionoxyethoxycarbonylmethyl) O-ethyl xanthate (3), with an activated halide group and a xanthate group in the molecule were synthesized. The activated halide group was used as an ATRP initiator to initiate polymerization of St, and the xanthate group was used as a RAFT agent to mediate polymerization of VAc. Thus, 2 was first used to mediate the radical polymerization of VAc, followed by ATRP of St, while 3 was used first to initiate the ATRP of St, followed by the RAFT polymerization of VAc. Both approaches indicate that either the radical polymerization of St or that of VAc is controlled, and well-defined PVAc-b-PSt is obtained as confirmed by gel permeation chromatography and NMR measurements.
Co-reporter:Wenxi Ji, Jingjing Yan, Erqiang Chen, Zichen Li and Dehai Liang
Macromolecules 2008 Volume 41(Issue 13) pp:4914-4919
Publication Date(Web):2017-2-22
DOI:10.1021/ma8005312
The polymerization-induced micellization of poly(ethylene oxide)-b-poly(styrene-alt-maleic anhydride) (PEO-b-P(S-alt-MAn)) in CHCl3 was monitored in situ by laser light scattering. Reversible addition−fragmentation chain transfer (RAFT) polymerization was used to grow the P(S-alt-MAn) block onto the PEO macromolecular chain transfer agents (macro-CTAs) at 55 °C. The whole process underwent three stages over time: the induction period, the formation of loose aggregates, and the formation of micelles. The polymerization process and the micellization process were affected mutually: the increase in the degree of polymerization induced the micellization of PEO-b-P(S-alt-MAn); meanwhile, the formation of core−shell micelles retarded the polymerization rate. At higher polymer concentrations, the mutual effect was even stronger, where smaller size micelles with higher density were obtained.
Co-reporter:Song Lin, Fusheng Du, Yang Wang, Shouping Ji, Dehai Liang, Lei Yu and Zichen Li
Biomacromolecules 2008 Volume 9(Issue 1) pp:
Publication Date(Web):December 19, 2007
DOI:10.1021/bm7008747
Intelligent gene delivery systems based on physiologically triggered reversible shielding technology have evinced enormous interest due to their potential in vivo applications. In the present work, an acid-labile block copolymer consisting of poly(ethylene glycol) and poly(2-(dimethylamino)ethyl methacrylate) segments connected through a cyclic ortho ester linkage (PEG-a-PDMAEMA) was synthesized by atom transfer radical polymerization of DMAEMA using a PEG macroinitiator with an acid-cleavable end group. PEG-a-PDMAEMA condensed with plasmid DNA formed polyplex nanoparticles with an acid-triggered reversible PEG shield. The pH-dependent shielding/deshielding effect of PEG chains on the polyplex particles were evaluated by ζ potential and size measurements. At pH 7.4, polyplexes generated from PEG-a-PDMAEMA exhibited smaller particle size, lower surface charge, reduced interaction with erythrocytes, and less cytotoxicity compared to PDMAEMA-derived polyplexes. At pH 5.0, ζ potential of polyplexes formed from PEG-a-PDMAEMA increased, leveled up after 2 h of incubation and gradual aggregation occurred in the presence of bovine serum albumin (BSA). In contrast, the stably shielded polyplexes formed by DNA and an acid-stable block copolymer, PEG-b-PDMAEMA, did not change in size and ζ potential in 6 h. In vitro transfection efficiency of the acid-labile copolymer greatly increased after 6 h incubation at pH 5.0, approaching the same level of PDMAEMA, whereas there was only slight increase in efficiency for the stable copolymer, PEG-b-PDMAEMA.
Co-reporter:Xiaonan Huang, Fusheng Du, Dehai Liang, Shrong-Shi Lin and Zichen Li
Macromolecules 2008 Volume 41(Issue 14) pp:5433-5440
Publication Date(Web):June 21, 2008
DOI:10.1021/ma800783v
Two acid-labile, thermoresponsive poly(methacrylamide)s with the pendant cyclic orthoester moieties of trans and cis configurations, PtNEM and PcNEM, were synthesized via free radical polymerization of the corresponding trans and cis isomers of N-(2-ethoxy-1,3-dioxan-5-yl)methacrylamide (NEM). The thermally induced phase transition/separation behaviors of both polymers as well as the aqueous solution properties below and above their phase transition temperatures were investigated by means of turbidimetry, DSC, 1H NMR, microscopy, fluorescence probe, and dynamic light scattering. Both PtNEM and PcNEM showed aggregation behaviors below their respective LCSTs, and the former formed more hydrophobic microdomains which had greater capability to solvate pyrene molecules compared with PcNEM. These two polymers exhibited thermally induced sensitive and reversible phase transitions in aqueous solution. PtNEM showed a little lower cloud point but much greater phase transition enthalpy compared to PcNEM. The results of DSC, 1H NMR, and microscopy measurements revealed that PcNEM exhibited a liquid−liquid phase separation while PtNEM likely underwent a liquid−solid transition. Furthermore, the pH-dependent hydrolyses of both polymers were studied by the 1H NMR and turbidimetric approaches. The results indicated that both PtNEM and PcNEM showed acid-triggered hydrolysis behaviors, and the hydrolysis products were affected by the configurations of the pendant cyclic groups. On the basis of these results, we can conclude that the stereochemical structures of the pendant cyclic orthoester groups in these poly(methacrylamide)s greatly affect their aqueous solution properties as well as their hydrolysis behaviors.
Co-reporter:Fusheng Du;Xiaonan Huang;Rong Ju;Zichen Li
Macromolecular Rapid Communications 2007 Volume 28(Issue 5) pp:597-603
Publication Date(Web):12 MAR 2007
DOI:10.1002/marc.200600798
Novel acid-labile, thermoresponsive methacrylamide-based (co)polymers with pendent ortho ester groups were prepared by free radical polymerization of N-(2-methoxy-1,3-dioxan-5-yl) methacrylamide (NMM) and N-(2-ethoxy-1,3-dioxan-5-yl)methacrylamide (NEM). These polymers are both thermoresponsive and acid-sensitive in aqueous solution, which was proved by transmittance measurements, fluorescence, and 1H NMR spectroscopy. The LCSTs of the (co)polymers were shifted to higher temperature by increasing the content of the more hydrophilic NMM units. All of these polymers can be hydrolyzed under acidic condition and the hydrolysis rate increased with the decrease in the pH value.
Co-reporter:Ning Xu;Feng-Zhu Lu;Fu-Sheng Du
Macromolecular Chemistry and Physics 2007 Volume 208(Issue 7) pp:730-738
Publication Date(Web):5 APR 2007
DOI:10.1002/macp.200600533
Maleimido-terminated PCL (M-PCL) and alkyne-terminated PCL (A-PCL) are prepared by the ring-opening polymerization of ε-caprolactone with N-hydroxyethyl maleimide and 4-pentyn-1-ol as initiators catalyzed by tin(II) trifluoromethane sulfonate at 25 °C, respectively. A series of saccharide-terminated PCLs have also been synthesized under mild conditions by two chemical strategies: 1). Michael addition of M-PCL and amino-containing maltose, and 2). a ‘click’ reaction of A-PCL and azide-containing saccharide. The amphiphilic nature of these maltose-terminated PCLs make self-assembly into aggregates in water possible. These aggregates have been characterized by transmission electron microscopy and dynamic light scattering measurements.
Co-reporter:Zi-Chen Li;Ning Xu;Fu-Sheng Du
Journal of Polymer Science Part A: Polymer Chemistry 2007 Volume 45(Issue 10) pp:1889-1898
Publication Date(Web):29 MAR 2007
DOI:10.1002/pola.21949
A series of poly(L-lysine)s grafted with aliphatic polyesters, poly(L-lysine)-graft-poly(L-lactide) (PLy-g-PLLA) and poly(L-lysine)-graft-poly(ϵ-caprolactone) (PLy- g-PCL), were synthesized through the Michael addition of poly(L-lysine) and maleimido-terminated poly(L-lactide) or poly(ϵ-caprolactone). The graft density of the polyesters could be adjusted by the variation of the feed ratio of poly(L-lysine) to the maleimido-terminated polyesters. IR spectra of PLy-g-PCL showed that the graft copolymers adopted an α-helix conformation in the solid state. Differential scanning calorimetry measurements of the two kinds of graft copolymers indicated that the glass transition temperature of PLy-g-PLLA and the melting temperature of PLy-g-PCL increased with the increasing graft density of the polyesters on the backbone of poly(L-lysine). Circular dichroism analysis of PLy-g-PCL in water demonstrated that the graft copolymer existed in a random-coil conformation at pH 6 and as an α-helix at pH 9. In addition, PLy-g-PCL was found to form micelles to vesicles in an aqueous medium with the increasing graft density of poly(ϵ-caprolactone). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1889–1898, 2007
Co-reporter:Xin Zhang, Zi-Chen Li, Kai-Bo Li, Song Lin, Fu-Sheng Du, Fu-Mian Li
Progress in Polymer Science 2006 Volume 31(Issue 10) pp:893-948
Publication Date(Web):October 2006
DOI:10.1016/j.progpolymsci.2006.08.009
This review describes two classes of vinyl monomers bearing chromophores and their polymers based on the electron-accepting (A) or electron-donating (D) properties of vinyl double bonds, i.e., electron-poor vinyl monomers bearing electron-donating chromophores ([A(=)]n–D), and electron-rich vinyl monomers bearing electron-accepting chromophores ([D(=)]n–A). These D/A monomers generally display no or weak fluorescence, while their saturated analogs and polymers show strong fluorescence at the same chromophore concentration. This fluorescence structural self-quenching effect is attributed to an intramolecular charge transfer interaction. The polymerizable double bonds play a key role in the structural self-quenching. The fluorescence structural self-quenching is strongly correlated with the interaction strength and spacer length between A and D units, and solvent properties. Emphasis is laid on a special class of vinyl monomers with strong electron-accepting ability, i.e., maleimides, and their synthesis, polymerization, and photochemical and photophysical properties. Various macromolecular architectures of maleimides are described in detail. Several practical applications exemplify the photochemical and photophysical behavior of these D/A monomers and their polymers.
Co-reporter:Zi-Chen Li;Xin Zhang;Hao-Ling Sun;Zheng He;Kai-Bo Li;Liu-He Wei;Fu-Sheng Du;Song Lin;Fu-Mian Li;Zhe-Ming Wang
Journal of Polymer Science Part A: Polymer Chemistry 2006 Volume 44(Issue 1) pp:304-313
Publication Date(Web):14 NOV 2005
DOI:10.1002/pola.21113
Mono-, bis-, and trismaleimides (MM-2, BM-4, and TM-6, respectively) bearing electron-donating chromophores generally displayed strong fluorescence quenching. The quenching mechanism of fluorescence was revealed by electrochemical studies. On the basis of the electrochemical data, an energy level diagram was established for these maleimides. The electron-donating ability increased in the order of TM-6 < BM-4 < MM-2. The electron-accepting ability increased in the opposite order, that is, from MM-2 to BM-4 to TM-6. The copolymerization of multimaleimides with diamine could be well monitored by fluorescence spectroscopy. Compared with fluorescence probe techniques, the fluorescence monitoring could directly reflect the consumption of CC bonds. Furthermore, a novel trismaleimide resin was preliminarily studied, in which TM-6 was a dual-purpose functional monomer acting not only as a crosslinker but also as an intrinsic fluorophore to monitor its crosslinking or cure process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 304–313, 2006
Co-reporter:Feng-Zhu Lu;Jian-Qiang Meng;Fu-Sheng Du;Bao-Yan Zhang
Macromolecular Chemistry and Physics 2005 Volume 206(Issue 4) pp:
Publication Date(Web):14 FEB 2005
DOI:10.1002/macp.200400354
Summary: A pyrene end-labeled amphiphilic block copolymer, poly(ε-caprolactone)-block-poly[6-O-(4-vinylbenzyl)-D-galactose] (Py-PCL-b-PVBG), was synthesized by a four-step method. The aggregation behavior of the diblock copolymer in solution was studied by monitoring the fluorescence of pyrene. TEM measurements revealed that the aggregates obtained by first dissolving the copolymer in N,N-dimethylformamide (DMF), followed by the addition of water, were primarily spheres with the PCL blocks in the core. The PVBG corona was then crosslinked with glutaraldehyde. Final removal of the PCL core was accomplished by degradation under basic conditions, which resulted in the formation of hollow glycopolymer nanospheres.
Co-reporter:Jian-Qiang Meng;Ya-Shu Liu;Fu-Sheng Du
Journal of Polymer Science Part A: Polymer Chemistry 2005 Volume 43(Issue 4) pp:752-762
Publication Date(Web):5 JAN 2005
DOI:10.1002/pola.20568
A detailed exploration of the atom transfer radical polymerization (ATRP) of a sugar-carrying monomer, 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene-D-galactopyranose (MAIPGal) was performed. The factors pertinent to ATRP, such as initiators, ligands, catalysts, and temperature were optimized to obtain good control over the polymerization. The kinetics were examined in detail when the polymerization was initiated by methyl 2-bromoisopropionate (2-MBP), ethyl 2-bromoisobutyrate (2-EBiB), or a macroinitiator, [α-(2-bromoisobutyrylate)-ω-methyl PEO] (PEO–Br), with bipyridine (bipy) as the ligand at 60 °C or by 2-EiBB with N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) as the ligand at room temperature (23 °C). The effects of the catalysts (CuBr and CuCl) were also investigated. We demonstrate that the successful ATRP of MAIPGal can be achieved for 2-EBiB/CuBr/bipy and 2-MBP/CuCl/bipy at 60 °C and for 2-EBiB/CuBr/PMDETA at room temperature. The initiation by 2-EBiB at room temperature with PMDETA as the ligand should be the most optimum operation for its moderate condition and suppression of many side reactions. Chain extension of P(MAIPGal) prepared by ATRP with methyl methacrylate (MMA) as the second monomer was carried out and a diblock copolymer, P(MAIPGal)-b-PMMA, was obtained. Functional polymers, poly(D-galactose 6-methacrylate) (PGMA), PEO-b-PGMA, and PGMA-b-PMMA were obtained after removal of the protecting groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 752–762, 2005
Co-reporter:Zi-Chen Li, Yu-Zeng Liang and Fu-Mian Li
New Journal of Chemistry 2002 vol. 26(Issue 12) pp:1805-1810
Publication Date(Web):29 Oct 2002
DOI:10.1039/B110614G
Polystyrene-block-poly[2-(β-D-glucosyloxy)ethyl acrylate]
(PS-b-PGEA) can form a variety of molecular assemblies in aqueous media when initially dissolved in water-soluble organic solvents, such as N,N-dimethylformamide (DMF), THF, etc. The morphologies of these molecular assemblies are affected by the copolymer composition, the nature of the solvent and the initial copolymer concentration. Thus, morphological transformations can be realized by varying the above parameters. In this paper, the effects of additives, such as glucose, HCl, Concanavalin A
(Con A), and CaCl2, on the aggregates of PS-b-PGEA in dilute aqueous solutions have been investigated. PS77-b-PGEA6 yielded predominantly spheres in water when initially dissolved in DMF at a concentration of 0.1–0.2 wt %. A transformation of the morphology to bilayer structures upon addition of different amounts of glucose, HCl, Con A or CaCl2 was observed. The morphological transitions can be ascribed to the decrease of the repulsive interactions among corona-forming blocks.
Co-reporter:Xiang-Yuan Xiong;Wei He;Fu-Mian Li
Chinese Journal of Chemistry 2001 Volume 19(Issue 11) pp:
Publication Date(Web):26 AUG 2010
DOI:10.1002/cjoc.20010191118
Three double-chain amphiphiles with amino acid groups as hydrophilic moiety were synthesized. These amphiphiles can be easily dispersed in buffer solution to form transparent dispersion. Examination of the dispersion by transmission electron microscopy (TEM) showed the formation of stable vesicular aggregates, which was also confirmed by the ability to encapsulate water-soluble dyes. Since amino acid groups are located on the surface of the vesicles, water-soluble carbodiimide can induce the condensation of these groups to form peptide. The phase transition temperatures of these vesicles were estimated by differential scanning calorimetry (DSC), and a decrease of phase transition temperature was observed after polycondensation due to the disturbance of the ordered arrangement of the hydrophobic chains. The leakage rate of the vesicles before and after condensation was studied by monitoring the increase of fluorescence intensity of water-soluble dye. These vesicles belong to the least permeable ones and the leakage rate can be controlled by varying the degree of condensation or the temperature.
Co-reporter:Lei Li, An Lv, Xin-Xing Deng, Fu-Sheng Du and Zi-Chen Li
Chemical Communications 2013 - vol. 49(Issue 76) pp:NaN8551-8551
Publication Date(Web):2013/07/30
DOI:10.1039/C3CC44557G
Passerini three-component reaction and multicomponent polymerization (MCP) were demonstrated to be facile methods for the preparation of photo-cleavable polymers, photo- and redox-dually cleavable polymers, as well as block copolymers.
Co-reporter:Cheng-Cheng Song, Fu-Sheng Du and Zi-Chen Li
Journal of Materials Chemistry A 2014 - vol. 2(Issue 22) pp:NaN3426-3426
Publication Date(Web):2014/03/04
DOI:10.1039/C3TB21725F
Reactive oxygen species (ROS) play key roles in many physiological processes, such as cell signaling and host innate immunity. However, when they are overproduced, ROS may damage biomolecules in vivo and cause diseases such as cardiovascular or neurodegenerative diseases, cancer, and so forth. Oxidative stress is usually implicated in various inflammatory tissues, representing an important target for the development of various therapeutic strategies. Therefore, various probes for the in vitro detection of ROS or the in vivo diagnosis of the oxidative stress-relevant diseases have been developed. Oxidation-responsive polymers have also attracted great interest due to their potential applications in biomedical fields. In this feature article, we summarize six types of oxidation-responsive polymers based on different oxidation-responsive motifs. Poly(propylene sulfide)s, selenium-based polymers, aryl oxalate- and phenylboronic ester-containing polymers are discussed in detail, while poly(thioketal)s and proline-containing polymeric scaffolds are briefly introduced.
Co-reporter:Li-Jing Zhang ; Bo-Tao Dong ; Fu-Sheng Du
Macromolecules () pp:
Publication Date(Web):October 31, 2012
DOI:10.1021/ma3016213
Three types of linear polyesters containing monodisperse methoxy oligo(ethylene glycol)s (mOEG, x = 6, 7, or 8) side chains (P1-mOEG, P2-mOEG, and P3-mOEG) have been synthesized by atom transfer radical polyaddition and click chemistry. Degradable disulfide and ketal groups were incorporated into the polymer backbone of P2-mOEG and P3-mOEG respectively. All of these three series of mOEG-grafted polyesters are water-soluble and display reversible thermoresponsive properties with tunable cloud point (CP). Aqueous solution properties and thermo-induced phase transitions were studied by 1H NMR, turbidimetry, DLS, and fluorescence probe method. The results indicate that these polyesters mainly adopt single chain conformations in aqueous solution below CP. OEG length has a significant effect on the CP, the CP increases by ca. 10 °C when the repeating units of OEG side chains increase from 6 to 7, and by ca. 6 °C when they increase from 7 to 8. The main chain structures also affect the CP values, which decrease from P1-mOEG to P3-mOEG due to the increased hydrophobicity of the backbone. Degradation of the polymers was conducted under basic, reductive and mild acidic conditions, respectively. The degradation products also show thermoresponsive behaviors, but the CP values vary from the precursor polymers depending on the alteration of hydrophilic/hydrophobic balance and shielding effect of the OEG side chain.
Co-reporter:Ning Yan, Jiaguang Zhang, Yuan Yuan, Guang-Tao Chen, Paul. J. Dyson, Zi-Chen Li and Yuan Kou
Chemical Communications 2010 - vol. 46(Issue 10) pp:NaN1633-1633
Publication Date(Web):2010/02/03
DOI:10.1039/B923290G
Two thermoresponsive polymers based on alkyl modified poly-vinylpyrrolidone (PVP) that exhibit very sensitive and reversible temperature-dependant water solubility are described. The application of these polymers as Au nanocatalyst stabilizers leads to a “smart” thermoresponsive Au nanoparticlecatalyst.
Co-reporter:Rui Wang, Ning Xu, Fu-Sheng Du and Zi-Chen Li
Chemical Communications 2010 - vol. 46(Issue 22) pp:NaN3904-3904
Publication Date(Web):2010/04/21
DOI:10.1039/C002473B
A mannose-modified polylysine was synthesized, the self-assembly of which in aqueous solution led to the formation of spherical micelles, vesicles and rod-like micelles in a controlled manner by simply changing the solution pH and adding a surfactant to the solution.
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