Co-reporter:Jianbing Huang, Hanjun Zhu, Hui Liang and Jiang Lu
Polymer Chemistry 2016 vol. 7(Issue 29) pp:4761-4770
Publication Date(Web):24 Jun 2016
DOI:10.1039/C6PY00794E
Salicylaldehyde-functionalized diblock copolymer nano-objects were synthesized by polymerization induced self-assembly (PISA) via RAFT dispersion polymerization of a newly designed core-forming monomer, 3-formyl-4-hydroxybenzyl methacrylate (FHMA), using the poly(2-hydroxypropyl methacrylate) (PHPMA) macromolecular chain transfer agent as a steric stabilizer in methanol at 65 °C. A range of PHPMA-b-PFHMA block copolymer morphologies including spheres, worms and vesicles could be accessed by adjusting the degree of polymerization of the core forming PFHMA block. Since the salicylaldehyde groups of core-forming PFHMA blocks could react with hydrazine in a 2:1 stoichiometry to form salicylaldazines with aggregation-induced emission, one-step post-modification of the PISA nano-objects using hydrazine enabled their inherent nanostructures to be stabilized via covalent cross-linking and simultaneously conferred luminescent features on the resulting stabilized nanoparticles. Solid nano-objects, obtained easily via precipitation into diethyl ether, could be re-dispersed well in methanol and THF. The nano-objects could also be re-dispersed in water to form colloidal dispersions at a low concentration (≤1% w/w). Thanks to the stability imparted by the cross-linking, the morphologies of the preformed PISA nano-objects remained intact even after re-dispersing these cross-linked nano-objects in THF (a good solvent for both blocks). The stabilized nano-objects displayed strong orange fluorescence in water, organic solvents or solid state. This work opens the possibility for simultaneous functionalization and stabilization of PISA-generated block copolymer nano-objects.
Co-reporter:Jianbing Huang, Hui Liang, Du Cheng and Jiang Lu
Polymer Chemistry 2016 vol. 7(Issue 9) pp:1792-1802
Publication Date(Web):27 Jan 2016
DOI:10.1039/C5PY01656H
A facile synthetic pathway to polypeptide–PEG miktoarm star copolymers with a fluorescently labeled core has been developed by combination of the reversible addition-fragmentation chain transfer (RAFT) arm-first technique and an aldehyde–aminooxy click reaction. A star polymer backbone with a fluorescently labeled and aldehyde-functionalized core was prepared via the cross-linking of a PEG macro-RAFT agent using an aldehyde-bearing divinyl monomer, 6,6′-(ethane-1,2-diylbis(oxy))bis(3-vinylbenzaldehyde), in combination with a fluorescent aluminum tris(8-hydroxyquinoline)-bearing cross-linker. The aldehyde groups on the core were then coupled with the newly designed aminooxy terminated poly(γ-benzyl-L-glutamate) (PBLG-ONH2) to generate the fluorescently labeled PBLG–PEG miktoarm star copolymer. Further aminolysis of the benzyl groups of PBLG arms with β-hydroxyethylenediamine endowed the miktoarm star polymer with the ability to capture negatively charged siRNA via electrostatic interactions. Owing to the biocompatible polypeptide and PEG arms, the obtained miktoarm star polymer exhibited low cytotoxicity. The miktoarm star polymer/siRNA complexes (formed at N/P ratio = 16) showed a relatively small particle size and appropriate positive zeta potentials, facilitating the cellular uptake. Besides, with its fluorescent property, the star polymer could serve as a probe for cellular tracing. This multifunctional star polymer would thus be of particular interest because of its promising potential in, for example, simultaneous gene delivery and bioimaging.
Co-reporter:Jianbing Huang, Lvhuan Lin, Hui Liang and Jiang Lu
Polymer Chemistry 2015 vol. 6(Issue 21) pp:4020-4029
Publication Date(Web):21 Apr 2015
DOI:10.1039/C5PY00436E
A facile synthetic route to branched graft copolymers has been developed by combination of self-condensing vinyl polymerization (SCVP), reversible addition–fragmentation chain transfer (RAFT) polymerization and aldehyde–aminooxy reaction. RAFT polymerization of 2-(dimethylamino)ethyl methacrylate (DEM) in the presence of a newly designed aldehyde-containing chain-transfer monomer, 6-(2-formyl-4-vinylphenoxy)hexyl-2-(dodecylthiocarbonothioylthio)-2-methylpropanate (FHDM), led to branched polyDEM (BPDEM) bearing aldehyde functionalities on its branching points. The degree of branching and the average branch length of the resulting BPDEM can be readily tuned by manipulation of the DEM/FHDM feed ratio. The aldehyde groups on the branching points of BPDEM were then reacted with aminooxy-terminated poly(ethylene oxide)s (PEO-ONH2), affording the structurally well-defined branched graft copolymer BPDEM-g-PEO with a branched polyDEM backbone and PEO grafted chains. The thermo-induced micellization behavior of BPDEM-g-PEO in water was investigated. Opportunities are open for BPDEM-g-PEO to form either multimolecular micelles or unimolecular micelles via simply adjusting the chain length of grafted PEO. Further modification of BPDEM-g-PEO by quaternization resulted in branched cationic polyelectrolytes which are capable of capturing negatively charged guest molecules via electrostatic complexation to form in situ self-assembled nanoparticles with simultaneous encapsulation of the guests.
Co-reporter:Qiangfang He, Jianbing Huang, Hui Liang and Jiang Lu
Polymer Chemistry 2014 vol. 5(Issue 14) pp:4348-4357
Publication Date(Web):01 Apr 2014
DOI:10.1039/C4PY00053F
A well-defined block copolymer polystyrene-block-poly(2-hydroxy-5-vinylbenzaldehyde) (PS-b-PHVB) was synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization of HVB using a trithiocarbonate terminated polystyrene macro-chain transfer agent. Sequential grafting of monoamine-terminated PEG (PEG–NH2) and 2-(2-aminoethoxy)ethanol (AME) onto the HVB blocks of PS-b-PHVB via aldehyde–amine condensation afforded an amphiphilic block copolymer PS-b-(PHVB-g-PEG-and-AME) bearing a pendant salicylidene Schiff base with a precise structure. PS-b-(PHVB-g-PEG-and-AME) could self-assemble in ethanol into micelles with salicylidene Schiff base groups at the core–shell interface. Addition of Zn2+ ions into the resulting micellar solution not only endowed the micelles with fluorescent features but also enabled the resulting luminescent micelles to be stabilized through ionic cross-linking in consequence of the salicylaldimine–Zn2+ complexation. The obtained fluorescent cross-linked micelle was “light-controllable” in terms of its fluorescence emission and cross-linking structure due to the reversibility of the salicylaldimine–Zn2+ coordinative bond in response to light stimuli. The reversible fluorescence decrease and recovery could be achieved periodically upon alternative 254 nm UV irradiation and maintaining in the dark, and the micelles could be de-stabilized by UV irradiation-induced de-cross-linking. The capture of guest molecules and the light-triggered release of the guests for this Zn2+ coordinated micelle were also demonstrated using the coumarin-153 dye as a model guest molecule.
Co-reporter:Jianbing Huang;Zhongpeng Xiao;Hui Liang,
Polymer International 2014 Volume 63( Issue 6) pp:1122-1128
Publication Date(Web):
DOI:10.1002/pi.4625
Abstract
A facile synthetic pathway to a multi-arm star graft polymer has been developed via a grafting-onto strategy using a combination of a reversible addition–fragmentation chain transfer (RAFT) arm-first technique and aldehyde–aminooxy click reaction. A star backbone bearing aldehyde groups was prepared by the RAFT copolymerization of acrolein (Ac), an existing commercial aldehyde-bearing monomer, with styrene (St), followed by crosslinking of the resultant poly(St-co-Ac) macro-RAFT agent using divinylbenzene. The aldehyde groups on the star backbone were then used as clickable sites to attach poly(ethylene glycol) (PEG) side chains via the click reaction between the aldehyde groups and aminooxy-terminated PEG, leading to a structurally well-defined star graft copolymer with arms consisting of poly(St-co-Ac) as backbone and PEG as side chains. Crystalline morphology and self-assembly in water of the obtained star graft copolymer were also investigated. Opportunities are open for the star graft copolymer to form either multimolecular micelles or unimolecular micelles via control of the number of grafted PEG side chains. © 2013 Society of Chemical Industry
Co-reporter:Qiangfang He, Hui Liang and Jiang Lu
Polymer Chemistry 2013 vol. 4(Issue 5) pp:1557-1564
Publication Date(Web):04 Dec 2012
DOI:10.1039/C2PY20832F
Living/controlled polymerization of a salicylaldehyde-functionalized vinyl monomer, 2-hydrox-5-vinylbenzaldehyde (HVB), was achieved by reversible addition–fragmentation chain transfer (RAFT) polymerization with S-1-dodecyl-S′-(α,α′-dimethyl-α′′-acetic acid)trithiocarbonate as the RAFT agent in THF at 65 °C. The resulting well-defined polymer with pendant salicylaldehyde groups could react directly with mono-6-deoxy-6-aminoethyl-β-CD to yield a new β-CD-containing polymeric salicylidene Schiff base PHVB-graft-β-CD with precise structure and high solubility. PHVB-graft-β-CD was then coordinated with zinc ions to give the luminescent PHVB-graft-β-CD/Zn2+ complex which displayed intense blue fluorescence with a maximum emission peak around 452 nm in DMF. The obtained PHVB-graft-β-CD/Zn2+ tended to self-aggregate in aqueous media because of the hydrophobic nature of PHVB-graft-β-CD backbone, and therefore its fluorescence emission in water was weak as a result of the aggregation-induced fluorescence quenching. An obvious decrease of the aggregate size from 290 nm to 40 nm in aqueous media was observed after adding 1.0 equiv. (relative to β-CD moieties) of the guest molecule, sodium adamantanecarboxylate (Ad-COONa), and concomitantly a remarkable fluorescence enhancement (4.5-fold) was obtained due to a better water-dispersibility of PHVB-graft-β-CD/Zn2+. The incorporation of carboxylic groups on the PHVB-graft-β-CD/Zn2+ complex via the inclusion with Ad-COONa also endowed the resulting fluorescent nanoparticles with a further protein-binding function. Upon gradual addition of the fluorescent nanoparticle aqueous dispersion to the BSA buffer solution, the fluorescence intensity at ∼349 nm corresponding to BSA decreased, while the fluorescence intensity of the nanoparticle at ∼429 nm increased through an isoemissive point at 388 nm, indicating the occurrence of efficient fluorescence resonance energy transfer (FRET) between the fluorescent nanoparticles and protein. This novel protein sensing capability would give the fluorescent nanoparticles great potential in biotechnology.
Co-reporter:Kunmin Yang, Hui Liang and Jiang Lu
Journal of Materials Chemistry A 2011 vol. 21(Issue 28) pp:10390-10398
Publication Date(Web):08 Jun 2011
DOI:10.1039/C1JM10261C
A well-defined multifunctional star polymer consisting of reactive and thermoresponsive poly(N-isopropylacrylamide-co-acrolein) arms and an aluminum tris(8-hydroxyquinoline) (Alq3)-bearing fluorescently labeled core was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization using the “arm-first” method. Acrolein, a commercially available aldehyde-bearing monomer, was copolymerized with N-isopropylacrylamide (NIPAM) via RAFT technique in a controlled way to give well-defined linear trithiocarbonate terminated poly(NIPAM-co-acrolein) macro-RAFT agent. The preformed linear macro-RAFT agent was then cross-linked by a tri-vinyl Alq3-containing cross-linker (Alq3 cross-linker) in conjunction with N,N′-methylenebisacrylamide to give the desired reactive, thermoresponsive, and fluorescently labeled star polymer. The resultant star polymer exhibits a lower critical solution temperature at ∼29.8 °C in water, and displays intense greenish-yellow fluorescence with maximum emission peak around 520 nm in both organic solvent (i.e., THF) and water. Moreover, the highly reactive aldehyde functions in the arms of the star polymer could provide the key intermediates to conjugate biomolecules, and the conjugation with an aminooxy-functionalized BSA model protein was also demonstrated as an example of how the novel star polymer can be utilized to conjugate bioactive molecules, constructing fluorescently labeled “smart” polymer-protein conjugates.
Co-reporter:Naiyu Xiao, Hui Liang and Jiang Lu
Soft Matter 2011 vol. 7(Issue 22) pp:10834-10840
Publication Date(Web):10 Oct 2011
DOI:10.1039/C1SM06181J
Well-defined aldehyde-functionalized glycopolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) copolymerization of 1,2:3,4-di-O-isopropylidene-6-O-(2′-formyl-4′-vinylphenyl)-D-galactopyranose (IVDG) and 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) using dicumyl peroxide as the initiator and 1-phenylethyl phenyldithioacetate as the RAFT agent at 130 °C in anisole. The resulting copolymers were found to be hydrolytically degradable due to their main-chain polyester structures. Removal of the protective isopropylidene groups from the sugar residues resulted in a novel amphiphilic copolymer with low cytotoxicity as confirmed by MTT assay against L929 cells. The deprotected copolymer could conjugate anticancer drug DOXvia an acid-labile Schiff base linkage to form DOX-loaded micelles in a high drug loading level (∼14 wt%) with pendent galactose moieties covering the surface. The size of the DOX-conjugated polymeric micelle was determined to be about 125 nm by dynamic light scattering. The in vitro release studies demonstrated that the release of DOX from the micelles manifested a strong dependence on the environment pH due to the acid-cleavable Schiff base linkage between the DOX and micelles. The DOX release was significantly faster at pH 5.0 compared to pH 7.4.
Co-reporter:Zhong-Peng Xiao, Zhi-Hong Cai, Hui Liang and Jiang Lu
Journal of Materials Chemistry A 2010 vol. 20(Issue 38) pp:8375-8381
Publication Date(Web):24 Aug 2010
DOI:10.1039/C0JM01453B
Well-defined amphiphilic block copolymers consisting of a hydrophilic poly(ethylene oxide) (PEO) block linked to a hydrophobic block with reactive aldehyde and redox-active ferrocene groups was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-formal-4-vinylphenyl ferrocenecarboxylate (FVFC) using a monomethoxy-terminated PEO-based macro-chain transfer agent. These amphiphilic block copolymers self-assembled into spherical micelles in aqueous solution, and their size clearly depended on the molecular weight of the PFVFC hydrophobic block, which could be controlled directly via the aforementioned RAFT polymerization. The availability of the synthesized amphiphilic block copolymer to conjugate bioactive molecules was confirmed via the reaction with an aminooxy model drug O-benzylhydroxylamine (BHA). The oxidation peak potential of the conjugates in cyclic voltammetry depended on the amount of the conjugated BHA, allowing one to quantify the degree of the conjugation simply by electrochemical measurement. Also, water-soluble (NH4)Ce(NO3)6 and NaHSO3 were used as the oxidizing and reducing agents, respectively, to explore the redox-controlled responsive behaviors of BHA conjugated PEO-b-PFVFC micelles using UV-vis spectroscopy, scanning electron microscopy and dynamic light scattering. This redox-responsive behavior would provide a prerequisite for redox-controlled release of encapsulants.
Co-reporter:Zhao-Mian Wu;Hui Liang;Wen-Li Deng
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 15) pp:3323-3330
Publication Date(Web):
DOI:10.1002/pola.24116
Abstract
A facile synthetic pathway to miktoarm star copolymers with multiple arms has been developed by combining reversible addition–fragmentation chain transfer (RAFT) arm-first technique and aldehyde–aminooxy “click” coupling reaction. Star polystyrene (PS) with aldehyde functionalized core was initially prepared by RAFT arm-first technique via crosslinking of the preformed linear macro-RAFT agents using a newly designed aldehyde-containing divinyl compound 6,6′-(ethane-1,2-diylbis(oxy))bis(3-vinylbenzaldehyde) (EVBA). It was then used as a multifunctional coupling agent for the subsequent formation of the second generation poly(ethylene glycol) (PEG) arms via the click coupling reaction between its aldehyde groups and aminooxy-terminated PEGs. The possible formation of PS-PEG miktoarm star copolymer with Janus-like segregated structure in cyclohexanone was also investigated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3323–3330, 2010
Co-reporter:Zhong-Peng Xiao;Kun-Min Yang;Hui Liang
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 3) pp:542-550
Publication Date(Web):
DOI:10.1002/pola.23752
Abstract
A reversible addition-fragmentation chain transfer (RAFT) agent was directly anchored onto Fe3O4 nanoparticles in a simple procedure using a ligand exchange reaction of S-1-dodecyl-S′-(α,α′-dimethyl-α″-acetic acid)trithiocarbonate with oleic acid initially present on the surface of pristine Fe3O4 nanoparticles. The RAFT agent-functionalized Fe3O4 nanoparticles were then used for the surface-initiated RAFT copolymerization of N-isopropylacrylamide and acrolein to fabricate structurally well-defined hybrid nanoparticles with reactive and thermoresponsive poly(N-isopropylacrylamide-co-acrolein) shell and magnetic Fe3O4 core. Evidence of a well-controlled surface-initiated RAFT copolymerization was gained from a linear increase of number-average molecular weight with overall monomer conversions and relatively narrow molecular weight distributions of the copolymers grown from the nanoparticles. The resulting novel magnetic, reactive, and thermoresponsive core-shell nanoparticles exhibited temperature-trigged magnetic separation behavior and high ability to immobilize model protein BSA. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 542–550, 2010
Co-reporter:Zhaomian Wu, Hui Liang and Jiang Lu
Macromolecules 2010 Volume 43(Issue 13) pp:5699-5705
Publication Date(Web):May 26, 2010
DOI:10.1021/ma100800b
A facile synthetic pathway to poly(N-isopropylacrylamide) (PNIPAM)−poly(ethylene glycol) (PEG) miktoarm star copolymers with multiple arms has been developed by combining reversible addition−fragmentation chain transfer (RAFT) polymerization and aldehyde−aminooxy “click” coupling reaction. Star PNIPAM with aldehyde functionalized core was initially prepared by the RAFT arm-first technique via cross-linking of the preformed linear macro-RAFT agents using a newly designed aldehyde-containing divinyl compound 6,6′-(ethane-1,2-diylbis(oxy))bis(3-vinylbenzaldehyde) (EVBA). It was then used as a multifunctional coupling agent for the subsequent formation of the second-generation PEG arms via the click coupling reaction between its aldehyde groups and aminooxy-terminated PEGs. The thermoresponsive micellization behavior of PNIPAM−PEG miktoarm star copolymer with different PEG arm numbers in water was also investigated. Opportunities are open for thermoinduced intermolecular or intramolecular micellization of PNIPAM−PEG miktoarm star copolymers via controlling the content ratio of PNIPAM and PEG, forming multimolecular micelles and unimolecular micelles, respectively.
Co-reporter:Nai-Yu Xiao, An-Long Li, Hui Liang and Jiang Lu
Macromolecules 2008 Volume 41(Issue 7) pp:2374-2380
Publication Date(Web):March 8, 2008
DOI:10.1021/ma702510n
A new aldehyde-functionalized glycomonomer, 1,2:3,4-di-O-isopropylidene-6-O-(2′- formyl-4′-vinylphenyl)-d-galactopyranose (IVDG), was designed and prepared. The “living”/controlled radical polymerization of IVDG was successfully achieved using 2,2′-azobis(isobutyronitrile) as the initiator and 1-phenylethyl dithiobenzoate as the reversible addition−fragmentation chain transfer (RAFT) agent at 60 °C in tetrahydrofuran. The polymerization followed first-order kinetics, the number-average molecular weight of the obtained polymers increased in direct proportion to the monomer conversion, and the molecular weight distribution was narrow (polydispersity index <1.1). Removal of protective isopropylidene groups from the sugar residue in polyIVDG was carried out quantitatively using 88% formic acid at room temperature, yielding a novel amphiphilic polymer containing both galactopyranose and aldehyde functionalities. These amphiphilic polymers self-assembled into well-defined aldehyde-bearing polymeric micelles in aqueous solution without recourse to any surfactant. The size of the micelles increased almost linearly with the molecular weight of polyIVDG precursor, which could be controlled directly via the aforementioned RAFT polymerization process. Protein-bioconjugated nanoparticles were also successfully prepared by the immobilization of bovine serum albumin (as a model protein) onto the aldehyde-functionalized micelles.
Co-reporter:Yi Wang;Qing Chen;Hui Liang
Polymer International 2007 Volume 56(Issue 12) pp:
Publication Date(Web):13 APR 2007
DOI:10.1002/pi.2294
The feasibility of the radical copolymerizations of β-pinene with three N-substituted maleimides, i.e. N-phenylmaleimide (PhMI), N-methylmaleimide (MeMI), and N-ethylmaleimide (EtMI), was clarified for the first time. The copolymerization rates decreased in the order PhMI > MeMI > EtMI. A marked penultimate effect on the activity of the N-substituted maleimide-terminated radicals was found in these copolymerizations. The penultimate monomer reactivity ratios evaluated by the nonlinear method were r1 = 0.10, r′1 = 8.30, r2 = r′2 = 0 for PhMI–β-pinene, r1 = 0.20, r′1 = 7.09, r2 = r′2 = 0 for MeMI–β-pinene, and r1 = 0.16, r′1 = 6.50, r2 = r′2 = 0 for EtMI–β-pinene. Furthermore, the possible controlled copolymerizations of β-pinene and N-substituted maleimides were then attempted via the reversible addition-fragmentation chain transfer (RAFT) technique. In the presence of RAFT agent 1-phenylethyl phenyldithioacetate, the copolymerization of β-pinene with MeMI or EtMI was retarded severely. However, much smaller retardation was observed in the RAFT copolymerization of β-pinene with PhMI, and, more importantly, the copolymerization exhibited typical features of a controlled system. The solvent effect on the RAFT copolymerization of β-pinene and PhMI was also investigated using matrix-assisted laser desorption ionization time-of-fight mass spectrometry (MALDI-TOF-MS) analysis. The results clearly indicated that copolymerization in tetrahydrofuran suffered from competitive transfer and termination side-reactions arising from the solvent in spite of the presence of the RAFT agent. Copyright © 2007 Society of Chemical Industry
Co-reporter:Peng Yu;An-Long Li;Hui Liang
Journal of Polymer Science Part A: Polymer Chemistry 2007 Volume 45(Issue 16) pp:3739-3746
Publication Date(Web):6 JUL 2007
DOI:10.1002/pola.22124
A series of easily accessible and stable Schiff-base nickel complexes (complex 1–4) in conjunction with methylaluminoxane (MAO) were employed for the synthesis of relatively high molecular weight β-pinene polymers at high temperature with high productivity. The ligand structure of the complex had a substantial effect on the polymerization in terms of the productivity and the molecular weight. With complex 4 in the presence of MAO, high molecular weight polymers of β-pinene (Mn ∼ 10,900) were obtained at 40 °C with an extremely high productivity up to 1.25 × 107 g polyβ-pinene/mol of Ni. 1H NMR analyses showed that the obtained β-pinene polymer was structurally identical to that formed by conventional cationic Lewis acid initiators. The polymerization was presumably initiated by the nickel cation formed by the reaction of the schiff-base nickel complex and MAO, while the propagation proceeded in a manner typical for a conventional carbocationic polymerization process. Direct evidence for the carbocationic polymerization was offered by the fact that quenching of the polymerization with methanol at a low monomer conversion resulted in incorporation of a methoxyl end group into the polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3739–3746, 2007
Co-reporter:An-Long Li, Xiao-Yan Wang, Hui Liang, Jiang Lu
Reactive and Functional Polymers (May 2007) Volume 67(Issue 5) pp:
Publication Date(Web):1 May 2007
DOI:10.1016/j.reactfunctpolym.2007.03.002
The feasibility of the radical copolymerization of β-pinene and n-butyl acrylate (n-BA) was clarified for the first time. β-pinene was found to undergo degradative chain transfer during the copolymerization. This degradative chain transfer became less competitive with the copolymerization by the addition of EtAlCl2, and the copolymer yield, β-pinene incorporation and molecular weight of the copolymer increased remarkably compared with the case in the absence of EtAlCl2. The monomer reactivity ratios evaluated by the nonlinear least-squares method were rβ-pinene ∼ 0 and rn-BA ∼ 2.2 in the absence of EtAlCl2, rβ-pinene ∼ 0 and rn-BA ∼ 0.86 in the presence of EtAlCl2 in bulk at 70 ˚C. Furthermore, the possible controlled copolymerization of β-pinene and n-butyl acrylate was then attempted via the reversible addition-fragmentation transfer (RAFT) technique. The copolymerization (fβ-pinene = 0.20) using 2-cyanopropyl-2-yl dithiobenzoate as the RAFT agent displayed the typical features of a controlled system, such as the first-order kinetics and the linear increase in molecular weight with the overall conversion. The livingness of the copolymer chains was further proved by using them as the macroinitiator for the chain extension with styrene by RAFT process.
Co-reporter:Kunmin Yang, Hui Liang and Jiang Lu
Journal of Materials Chemistry A 2011 - vol. 21(Issue 28) pp:NaN10398-10398
Publication Date(Web):2011/06/08
DOI:10.1039/C1JM10261C
A well-defined multifunctional star polymer consisting of reactive and thermoresponsive poly(N-isopropylacrylamide-co-acrolein) arms and an aluminum tris(8-hydroxyquinoline) (Alq3)-bearing fluorescently labeled core was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization using the “arm-first” method. Acrolein, a commercially available aldehyde-bearing monomer, was copolymerized with N-isopropylacrylamide (NIPAM) via RAFT technique in a controlled way to give well-defined linear trithiocarbonate terminated poly(NIPAM-co-acrolein) macro-RAFT agent. The preformed linear macro-RAFT agent was then cross-linked by a tri-vinyl Alq3-containing cross-linker (Alq3 cross-linker) in conjunction with N,N′-methylenebisacrylamide to give the desired reactive, thermoresponsive, and fluorescently labeled star polymer. The resultant star polymer exhibits a lower critical solution temperature at ∼29.8 °C in water, and displays intense greenish-yellow fluorescence with maximum emission peak around 520 nm in both organic solvent (i.e., THF) and water. Moreover, the highly reactive aldehyde functions in the arms of the star polymer could provide the key intermediates to conjugate biomolecules, and the conjugation with an aminooxy-functionalized BSA model protein was also demonstrated as an example of how the novel star polymer can be utilized to conjugate bioactive molecules, constructing fluorescently labeled “smart” polymer-protein conjugates.
Co-reporter:Zhong-Peng Xiao, Zhi-Hong Cai, Hui Liang and Jiang Lu
Journal of Materials Chemistry A 2010 - vol. 20(Issue 38) pp:NaN8381-8381
Publication Date(Web):2010/08/24
DOI:10.1039/C0JM01453B
Well-defined amphiphilic block copolymers consisting of a hydrophilic poly(ethylene oxide) (PEO) block linked to a hydrophobic block with reactive aldehyde and redox-active ferrocene groups was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-formal-4-vinylphenyl ferrocenecarboxylate (FVFC) using a monomethoxy-terminated PEO-based macro-chain transfer agent. These amphiphilic block copolymers self-assembled into spherical micelles in aqueous solution, and their size clearly depended on the molecular weight of the PFVFC hydrophobic block, which could be controlled directly via the aforementioned RAFT polymerization. The availability of the synthesized amphiphilic block copolymer to conjugate bioactive molecules was confirmed via the reaction with an aminooxy model drug O-benzylhydroxylamine (BHA). The oxidation peak potential of the conjugates in cyclic voltammetry depended on the amount of the conjugated BHA, allowing one to quantify the degree of the conjugation simply by electrochemical measurement. Also, water-soluble (NH4)Ce(NO3)6 and NaHSO3 were used as the oxidizing and reducing agents, respectively, to explore the redox-controlled responsive behaviors of BHA conjugated PEO-b-PFVFC micelles using UV-vis spectroscopy, scanning electron microscopy and dynamic light scattering. This redox-responsive behavior would provide a prerequisite for redox-controlled release of encapsulants.
