Co-reporter:Hai-Jie Ben;Wen-Zhu Cui;Cheng-Qi Ji;Fa Cheng
Industrial & Engineering Chemistry Research November 5, 2014 Volume 53(Issue 44) pp:17362-17369
Publication Date(Web):Publication Date (Web): October 13, 2014
DOI:10.1021/ie502676w
Aqueous core–shell latexes were synthesized through two-step emulsion copolymerization of vinylidene chloride (VDC) with ethyl acrylate (EA) and butyl acrylate (BA), respectively. First, seed latexes of EA-VDC85 copolymers with 85% VDC content were prepared by the binary emulsion copolymerization of VDC with EA. Subsequently, EA-VDC85 seed latexes were employed in the seed emulsion copolymerization of VDC with BA and the resulting BA-VDC80 copolymers with 80% VDC content covered onto EA-VDC85 seed latexes to form the core–shell latexes. Transmission electron microscopy and dynamic light scattering characterization demonstrated that the size and size uniformity of seed latexes were influenced markedly by the content of emulsifiers in the copolymerization, and higher emulsifier content led to smaller and more uniform latexes. Furthermore, only the utilization of homogeneous seed latexes in the seed emulsion polymerization could lead the majority of the formed latexes to bear the core–shell structure. These aqueous latexes were employed as coating films for the heavy-duty anticorrosion of metal. After 500 h of harsh salt-spray corrosion, electrochemical impedance spectroscopy measurement, corrosion evaluation around the scribe and adhesion tests demonstrated that the coating films (ca. 50 μm in thickness) formed by the optimal core–shell latexes could still protect steel plates well, and the adhesions of the coating films to steel plates were still the best. After 500 h of corrosion, the coating film formed by the best seed latex still showed good barrier properties; however, it lost adhesion to the steel plate. As for the coating film formed by the BA-VDC80 shell copolymer, both its barrier property and adhesion to steel sheet became poor after 500 h of corrosion. Therefore, it could be deduced that such aqueous core–shell latexes had more excellent comprehensive anticorrosion performances than the normal latexes composed of only the core or shell copolymers, and designing a suitable core–shell structure is also a good way to promote the heavy-duty anticorrosion performances of water-borne acylate-VDC copolymer latexes.
Co-reporter:Fa Cheng;Ce Fu;Tong-Xian Zhang;Wen-Zhu Cui
Industrial & Engineering Chemistry Research March 26, 2014 Volume 53(Issue 12) pp:4534-4543
Publication Date(Web):2017-2-22
DOI:10.1021/ie403396e
Aqueous latexes of copolymers of vinylidene chloride (VDC) with an acrylate, namely, methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), or 2-ethylhexyl acrylate (EHA), were employed to form a double-layer coating film for the heavy-duty anticorrosion of metal. Measurements of the water-vapor transmission rate and oxygen-gas transmission rate and electrochemical impedance spectroscopy (EIS) demonstrated that the barrier properties of MA–VDC and EA–VDC films were better than those of BA–VDC and EHA–VDC films. Among the MA–VDC and EA–VDC coatings, EA–VDC85 showed better comprehensive properties and, thus, was selected as the top layer of the designed double-layer coating film. Adhesion tests demonstrated that the BA–VDC and EA–VDC coatings had better adhesion to tinplates than the MA–VDC and EA–VDC coatings and, thus, were suitable for use as the bottom layer of the designed double-layer coating film. The characterizations of the double-layer coating films by adhesion tests and EIS showed that BA–VDC75 was the optimal bottom layer. Under harsh salt-spray corrosion conditions, the optimal double-layer coating film (ca. 50-μm thickness) with EA–VDC85 as the top layer and BA–VDC75 as the bottom layer could protect tinplate well for at least 800 h, and the adhesion of the coating film to the tinplate was still excellent even after 1000 h of corrosion. Scanning electron microscopy, differential scanning calorimetry, and Fourier-transform infrared spectroscopy were used to evaluate the corroded double-layer coating films.
Co-reporter:Bin Wang, Ting Xiao, Xiao-Bin Fu, Ting-Ting Jiang, Yu Chen, and Ye-Feng Yao
Macromolecules December 26, 2017 Volume 50(Issue 24) pp:9647-9647
Publication Date(Web):December 6, 2017
DOI:10.1021/acs.macromol.7b01887
The influence of stereochemical difference on the phase transition of thermoresponsive polymer was studied in detail in this work. To this end, we synthesized two thermoresponsive hyperbranched polymers having the almost same chemical composition but differing in the spatial distribution of the chemical groups. These samples exhibit remarkably different low critical solution temperatures (LCSTs). A detailed NMR study on the samples revealed that before the transition the chemical groups in the two samples have very different packing arrangements. A microscopic phase separation was realized in the polymer having the densely packed structure. The origin of the different LCSTs of the polymers was well explained by the entropy change due to the dehydrate/hydrate processes in the transition.
Co-reporter:Tong-Xian Zhang, Chen Zhan, Yu Chen, Li-Ping Yu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2017 Volume 535(Volume 535) pp:
Publication Date(Web):20 December 2017
DOI:10.1016/j.colsurfa.2017.09.048
Hyperbranched polymers were successfully used as reductant and stabilizer for the synthesis of stable water-soluble fluorescent gold nanoclusters (AuNCs) through a one-step bottom-up strategy. The hyperbranched polymers having such performance were acetamide terminated hyperbranched poly(amidoamines) (HPA-Acs) with disulfide functional groups. Small sized (less than 2 nm) AuNCs were formed under the optimal conditions of 80 °C, weak acidic condition (around pH 4.3) for 15–20 h. Through adjusting the feed ratio of HAuCl4 to HPA-Ac, the emitting light could be tuned from yellow to near-infrared. The measurements of UV–vis spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy further verified the formation of AuNCs. The quantum yields of the yellow and near-infrared fluorescent AuNCs were ca. 3.6% and 1.2%, respectively. The as-prepared AuNCs showed an excellent stability in a wide pH range (pH 2–12) and possessed low cytotoxicity for cancer HeLa cell, making it a suitable candidate for bioimaging.Download high-res image (196KB)Download full-size image
Co-reporter:Chen Zhan;Xiao-Bin Fu;Yefeng Yao;Hua-Ji Liu
RSC Advances (2011-Present) 2017 vol. 7(Issue 10) pp:5863-5871
Publication Date(Web):2017/01/16
DOI:10.1039/C6RA27390D
A series of hyperbranched poly(amidoamine)s (HPAs) were synthesized from the Michael addition copolymerization of tris(2-aminoethyl) amine (TAEA) and two bisacrylamide monomers N,N′-cystamine bisacrylamide (CBA) and N,N′-hexamethylene bisacrylamide (HMBA) at room temperature. The further modification with isobutyric anhydride led to isobutyramide terminated HPA (HPA-C4). 1H NMR and 15N NMR characterizations proved the successful preparation of these polymers. Moreover, beside the contents of TAEA, CBA and HMBA units in the composition, 15N NMR spectrometry could supply more structural information than 1H NMR spectrometry, such as the ratio of different amine groups in polymers, the transformation efficiency of reactive primary and secondary amines into C4 groups. GPC measurements not only gave the information of molecular weight and polydispersity, but also proved that all the HPA-C4s containing disulfide bonds could be degraded after being treated with dithiothreitol (DTT). Turbidimetry measurements showed that HPA-C4s had thermoresponsive property in water. The cloud point temperature (Tcp) of HPA-C4s was pH-dependent. Moreover, DTT could only affect the thermoresponsive property of HPA-C4s containing disulfide bonds due to the induced polymer degradation. Although no traditional fluorophores existed in HPA-C4s, HPA-C4s could emit blue fluorescence centered at ca. 455 nm. The fluorescence intensity was influenced pronouncedly by polymer concentration, pH, oxidizing time.
Co-reporter:Yao Zhang;Rui-Cong Wang;Hua-Ji Liu
Soft Matter (2005-Present) 2017 vol. 13(Issue 44) pp:8136-8143
Publication Date(Web):2017/11/15
DOI:10.1039/C7SM01862B
Polymers exhibiting an abnormal thermoresponsive behaviour, in which increase in the polymer concentration in water leads to an increase in the phase transition temperature, are few, and no plausible strategy has been addressed to prepare these polymers. For illuminating a feasible common strategy to prepare polymers with an abnormal thermoresponsive behaviour, in this study, we systematically prepared a series of hyperbranched polyglycerol (HPG) derivatives through a facile esterification reaction between HPG and aliphatic acids having different carbon numbers (X). Turbidimetry measurements demonstrate that thermoresponsive HPGs can be obtained only when HPGs are conjugated with aliphatic units of X ≤ 8. The conjugation of HPG with aliphatic units of X ≤ 4 resulted in thermoresponsive HPGs with a normal thermoresponsive behaviour. For the preparation of thermoresponsive HPGs with an abnormal thermoresponsive behaviour, X should be controlled in the range of 5–8. Fluorescence measurements with nile red as the fluorescent probe demonstrate that the existence of relatively strong hydrophobic interaction is a key factor to ensure that the polymer exhibits an abnormal thermoresponsive behaviour in water. Moreover, turbidimetry and fluorescence techniques are complementary for measuring the phase transition behaviour and suitable for different polymer concentration regions.
Co-reporter:You Fan, Ya-Qian Cai, Hua-Ji Liu, Yu Chen
Sensors and Actuators B: Chemical 2017 Volume 251(Volume 251) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.snb.2017.05.070
•CdS QDs were prepared by the assistance of HPEI-g-HPGs.•HPG shell of HPEI-g-HPGs affected the fluorescence of CdS QDs markedly.•HPG shell of HPEI-g-HPGs affected the selectivity to Hg2+ markedly.A series of hyperbranched graft copolymers with hyperbranched polyethylenimine (HPEI) as core and hyperbranched polyglycerol (HPG) as shell (HPEI-g-HPG) were used as nanoreactors and stabilizers for the synthesis of CdS quantum dots (QDs). The preparation conditions were optimized to obtain CdS QDs with a stronger fluorescence. Stable CdS QDs could be prepared by using HPEI-g-HPGs or HPEI homopolymer, but not HPG homopolymer. The CdS QDs capped by HPEI-g-HPGs emitted stronger than those capped by HPEI. Moreover, the photoluminescence intensity increased pronouncedly with increasing the HPG shell content of HPEI-g-HPG stabilizer. The measurements of UV–vis spectroscopy, transmission electron microscopy and dynamic light scattering further verified the formation of CdS QDs. Compared with the CdS QDs capped by HPEI, those capped by HPEI-g-HPGs showed a better storing stability in solution at 4 °C. The as-prepared CdS QDs were only stable in the pH range of 7.0–9.0. It was found that increasing the HPG shell content of HPEI-g-HPG stabilizer could effectively raise the selectivity of the as-prepared CdS QDs towards Hg2+. As the ratiometric fluorescence sensors, CdS QDs capped by HPEI-g-HPGs were most sensitive to Hg2+ and the limit of detection was ca. 1.5 × 10−8 M.Download high-res image (145KB)Download full-size image
Co-reporter:Wu-cheng Fang;Ran Zhang;Ye-feng Yao;Hua-ji Liu 刘华姬
Chinese Journal of Polymer Science 2017 Volume 35( Issue 8) pp:1035-1042
Publication Date(Web):25 June 2017
DOI:10.1007/s10118-017-1950-5
Optically active and inactive hyperbranched polymers with specific thermoresponsive behaviours in water were reported. Through two steps hyperbranched polyethylenimine (HPEI) polymers terminated with different amount of D-phenylalanine (D-Phe), L-phenylalanine (L-Phe) or DL-phenylalanine (DL-Phe) were prepared and characterized. The analyses on the solution properties by turbidimetry, dynamic light scattering, fluorescence probe and 1H-NMR demonstrated that all the polymers exhibited specific thermoresponsive behaviours in water, including: (1) In the dilute polymer concentration region, increasing the polymer concentration led to the increase of phase transition temperature; (2) The optically inactive thermoresponsive hyperbranched polymers showed a higher cloud-point temperature (Tcp) than their corresponding optically active ones in a relatively higher polymer concentration; (3) At the same polymer concentration the hydrophobic groups of the optically inactive HPEI-DL-Phe formed more perfect hydrophobic domain than those of the optically active HPEI-L-Phe and HPEI-D-Phe.
Co-reporter:Cuiyun Zhang, You Fan, Yunyi Zhang, Cong Yu, Hongfei Li, Yu ChenIan W. Hamley, Shichun Jiang
Macromolecules 2017 Volume 50(Issue 4) pp:
Publication Date(Web):February 10, 2017
DOI:10.1021/acs.macromol.6b02331
The self-assembly process of amphiphilic dendritic copolymers (ADPs) with a hydrophilic core and a hydrophobic shell was investigated via laser light scattering. The self-assembly occurs via a fast step and a slow step with different relaxation times. At the critical micelle concentration (CMC), the fusion of small micelles results in the rapid increase of the micelle size in the fast step. The slow step is associated with equilibrium through the fission and fusion of the micelles. The micelle size increases with the unimer concentration, which leads to a lower micelle concentration. The lower micelle concentration makes the relaxation time of the fast step increase with increasing unimer concentration. However, the fusion of larger micelles at higher concentration is more efficient to increase micelle size. The fusion of small micelles with large micelles at higher concentration accelerates the approaching equilibrium of the micelles except for the fission and fusion of micelles. With the increasing degree of amidation (DA), the relaxation time in the fast step increases and in the slow step it decreases.
Co-reporter:Bin Wang, Hua-Ji Liu and Yu Chen
RSC Advances 2016 vol. 6(Issue 3) pp:2141-2148
Publication Date(Web):22 Dec 2015
DOI:10.1039/C5RA20640E
Poly(N-vinylimidazole) (PVIm) that contains a large amount of bio-active imidazole units was used as the sole carbon source to synthesize PVIm-dot through a one-pot hydrothermal method without any further modification and surface passivation. The measurements of X-ray photoelectron spectroscopy, dynamic light scattering, transmission electron microscopy and X-ray diffraction proved that only a slight carbonization occurred during the hydrothermal treatment of PVIm. The characterizations of 1H NMR, FTIR and thermogravimetric analysis verified that the obtained PVIm-dot well inherited the chemical structure of its precursor PVIm. Unlike PVIm, the obtained PVIm-dot showed an obvious excitation-dependent photoluminescence (PL) behavior, and its PL features were quite stable at different pH values and ionic strength. The PVIm-dot possessed low cytotoxicity and could enter cancer cells, making it a suitable candidate for bio-imaging. Moreover, the PVIm-dot still kept the catalytic activity of its imidazole units. With the catalytic hydrolysis of p-nitrophenyl acetate as the model reaction, it was found that the PVIm-dot showed good catalytic activity in this reaction and its catalytic efficiency was better than PVIm. What's more, the variation of PL intensity during the reaction could be used as a luminescent sensor to monitor the progress of the hydrolysis reaction.
Co-reporter:You Fan, Ya-Qian Cai, Xiao-Bin Fu, Yefeng Yao, Yu Chen
Polymer 2016 Volume 107() pp:154-162
Publication Date(Web):19 December 2016
DOI:10.1016/j.polymer.2016.11.018
•Core-shell type hyperbranched grafting copolymers were prepared.•HPEI-g-HPGs could emit blue fluorescence.•The luminogen of HPEI-g-HPGs was assumed to be tertiary amine oxide.Hyperbranched polyethylenimine (HPEI) was modified with glycidol, resulting in hydroxyl terminated HPEI (HPEI-OH). Subsequently, HPEI-OH was used as the macroinitiator to initiate the anionic ring-opening polymerization of glycidol, realizing the hyperbranched grafting copolymer with HPEI as core and hyperbranched polyglycerol (HPG) as shell (HPEI-g-HPG) through the 'grafting from' method. The diagrams from gel permeation chromatography (GPC) showed that the products were a mixture of copolymers and homopolymers. A two-step purification method was developed to separate HPEI-g-HPGs from the mixture, which was much more effective than the normally-adopted dialysis method. The hyperbranched grafting polymerization condition was optimized and the maximal grafting efficiency was found to be ca. 30%. Under the optimal grafting polymerization condition, we prepared a series of HPEI-g-HPG copolymers that have the same HPEI core, but have a different number of glycidol units in the HPG shell. The detailed structural information of these copolymers was deduced from 1H NMR, inverse gated decoupled 13C NMR and GPC measurements. Although no traditional fluorophores existed in HPEI-g-HPGs, HPEI-g-HPGs could emit blue fluorescence centered at ca. 470 nm. The fluorescence intensity was influenced pronouncedly by the thickness of HPG shell, pH, oxidation time, the amount of THF in the solvent mixture. The detailed characterizations and analyses supported that the luminogen of HPEI-g-HPGs was tertiary amine oxide.
Co-reporter:Hua-ji Liu;Yue-yue Xu 陈宇
Chinese Journal of Polymer Science 2016 Volume 34( Issue 5) pp:585-593
Publication Date(Web):2016 April
DOI:10.1007/s10118-016-1779-3
The influence of sodium dodecyl sulfate (SDS) on the cloud point temperature (Tcp) of the aqueous solution of thermoresponsive hyperbranched polyethylenimine derivative HPEI-IBAm was studied systematically. When pH was below 8.5, HPEI-IBAm was positively-charged. Initially, the Tcp of HPEI-IBAm decreased significantly, followed by an obvious increase with the increase of SDS concentration. The lower the pH was, the higher the SDS concentration was required to achieve the minimum Tcp. When pH was above 8.5, HPEI-IBAm was neutral and raising the SDS concentration led to the gradual increase of Tcp. Compared to linear poly(N-isopropyl acrylamide) (PNIPAm), the Tcp of the current hyperbranched HPEI-IBAm was more sensitive to SDS. The thermoresponsive HPEI-IBAm/SDS complex was used as host to accommodate the non-polar pyrene in water. The lowest SDS concentration for effectively enhancing the solubility of pyrene in water was around 6.4 mmol·L-1. When HPEI-IBAm was present, the SDS concentration threshhold was decreased to about 0.31 mmol·L-1. Fluorescence technique with pyrene as the hydrophobic probe demonstrated that the SDS concentration of 7.2 mmol·L-1 was required to form the hydrophobic domain to accommodate pyrene guests without HPEI-IBAm, while only 0.2 mmol·L-1 of SDS was required in the presence of HPEI-IBAm.
Co-reporter:Jin-Ge Tong, Zhong-Yu Wei, Hao-Lin Yang, Zhen-Yu Yang, Yu Chen
Polymer 2016 Volume 84() pp:107-116
Publication Date(Web):10 February 2016
DOI:10.1016/j.polymer.2015.12.049
•Thermoresponsive hyperbranched polyampholytes were prepared.•The Tcp of hyperbranched polyampholytes was pH-dependent.•Thermoresponsive hyperbranched polyampholyte was good protein model.The amino groups of hyperbranched polyethylenimine (HPEI) were partially modified with isobutyric anhydride to introduce isobutyramide (IBAm) groups to HPEI, resulting in an LCST-type thermoresponsive HPEI-IBAm that is positively-charged or neutral depending on the media pH. Succinic acid (SA) units were further introduced to HPEI-IBAm through acylation with succinic anhydride, resulting in the hyperbranched polyampholyte, HPEI-IBAm-SA, with both amino and carboxylic acid groups. 1H NMR characterization proved the successful preparation of HPEI-IBAm-SA. Turbidimetry measurements showed that HPEI-IBAm-SA was also an LCST-type thermoresponsive polymer. The cloud point temperature (Tcp) of HPEI-IBAm-SA was pH-dependent. Compared with the HPEI-IBAm precursor, HPEI-IBAm-SA showed the thermoresponsive property in a wider pH range. At isoelectric point, HPEI-IBAm-SA had the lowest Tcp. The isoelectric point of HPEI-IBAm-SA could be tuned by controlling the amount of SA units, and the one with more SA units had a lower isoelectric point. Four halide anions with sodium as the counterion and four cations (Na+, K+, Mg2+ and Ca2+) with chloride as the counterion were used to measure the salt effects on the Tcp of HPEI-IBAm-SA. The specific ranking orderings of these ions in reducing the Tcp of HPEI-IBAm-SA were opposite at pH below and above isoelectric point. At pH above isoelectric point, the anion ranking is I− Mg2+ > Na+ ≈ K+. At pH below isoelectric point, and, the anion ranking is F−∼Cl− Mg2+ ≈ Ca2+. All the specific salt ordering found in HPEI-IBAm-SA system could be also found in the system of the protein representative, ovalbumin, implying that HPEI-IBAm-SA was a better protein model to mimic the interactions among ions and proteins with a different isoelectric point.
Co-reporter:Jia-Li Zhu, Yi Liu, Xun-Yong Liu, Hua-Ji Liu and Yu Chen
RSC Advances 2015 vol. 5(Issue 11) pp:8146-8151
Publication Date(Web):24 Dec 2014
DOI:10.1039/C4RA14020F
Silver nanoclusters (AgNCs) functionalized with hyperbranched polyethylenimines with a certain number of trimethylacetamide groups (PEI–TMA) were prepared through three steps. The influence of the preparation conditions, including the pH value in the mixture of PEI–TMA and Ag+ and the Ag+/PEI–TMA feed ratio, on the photoluminescence properties of the obtained nanocomposite of AgNCs and PEI–TMA (AgNC–PEI–TMA) was studied. The obtained AgNC–PEI–TMA nanocomposite was characterized by transmission electron microscopy, dynamic light scattering and zeta potential measurements, verifying the formation of the nanocomposite. AgNC–PEI–TMA in water was not only thermoresponsive, but also responded to other stimuli, including pH, inorganic salts, and loaded organic guest. The cloud point temperature (Tcp) of aqueous solutions of AgNC–PEI–TMA could be modulated through changing the pH, and varying the type and concentration of the inorganic salts and the loaded organic guest. The obtained AgNC–PEI–TMA nanocomposite was photoluminescent, and its maximum emission wavelength was not influenced by outside stimuli. Its emission intensity was influenced negligibly by pH, traditional salting-out anions (Cl− and SO42−), and the relatively polar aspirin guest. However, the traditional salting-in I− anion could quench its fluorescence a little.
Co-reporter:Yuan Yuan, Hua-Ji Liu and Yu Chen
RSC Advances 2015 vol. 5(Issue 121) pp:99646-99653
Publication Date(Web):10 Nov 2015
DOI:10.1039/C5RA18687K
The influences of hydrophilic dyes, including Congo Red (CR), Methyl Orange (MO), Eosin Y (EY), Fluorescein Sodium (FS) and Methylene Blue (MB), on the phase transition temperature (Tcp) of thermoresponsive hyperbranched polyethylenimine with many isobutyramide groups (HPEI-IBAm) were studied systematically. The cationic MB always showed a minor influence on the Tcp of both the cationic and the neutral HPEI-IBAm. According to the Tcp value at the 1:1 molar ratio of the dye to HPEI-IBAm, the ranking of these anionic dyes in reducing the Tcp of the cationic HPEI-IBAm (at pH 8) was CR > EY ≈ MO > FS. These anionic dyes could raise or have negligible influence on the Tcp of the neutral HPEI-IBAm (at pH 10) and their ranking in raising the Tcp of the neutral HPEI-IBAm was CR > EY > MO > FS. The pivotal interaction forces between HPEI-IBAm and the different hydrophilic dyes were interpreted through the combination of 2D 1H NMR characterization, zeta potential measurement and comparison with the influences of these dyes on the Tcp of the control thermoresponsive linear polymers. Cationic HPEI-IBAm was mixed with a mixture of anionic CR and cationic MB. The heating-induced cationic HPEI-IBAm precipitates the adsorbed CR molecules more efficiently from the CR/MB mixture that have a different effect on the Tcp. Moreover, the neutral HPEI-IBAm could separate the mixture of CR and FS molecules having a pronounced different efficiency in raising the Tcp.
Co-reporter:Chen Zhan;Si Li;Jin Cui 陈宇
Chinese Journal of Polymer Science 2015 Volume 33( Issue 6) pp:920-930
Publication Date(Web):2015 June
DOI:10.1007/s10118-015-1651-x
Hyperbranched polyamidoamines (HPAs) were directly employed as macroinitiators to initiate the Sn(Oct)2 catalyzed ring-opening polymerization of ɛ-caprolactone (CL), resulting in multiarm star copolymers with poly(ɛ-caprolactone) (PCL) as shells and HPA as core (HPA-b-PCL). From 1H-NMR characterization it was deduced that both the primary amines and the secondary amide groups of HPAs could initiate the CL polymerization, and the initiation efficiency increased when more CL monomers were fed. The average arm-numbers of the obtained stars were in the range of 115–353. Differential scanning calorimetry measurements demonstrated that the melting and crystallization temperatures, fusion and crystallization enthalpy and the degree of crystallinity of the star polymers increased as the PCL arm length increased. HPA-b-PCL stars could be used as nanocarriers to efficiently accommodate anionic dyes at acidic condition, while load cationic dyes at basic condition. Compared with the dye-loading behavior of multiarm star PCL with the neutral hyperbranched polyglycerol as core, it was deduced that HPA-b-PCL nanocarriers accommodated anionic dyes using the HPA core, while loaded cationic dyes using both the HPA core and the PCL shell. Dynamic light scattering analyses also supported such deduction. Furthermore, HPA-b-PCL nanocarriers could selectively load the anionic Eosin Y or the cationic methylene blue from their mixture at pH = 6 or 9, respectively, realizing their separation.
Co-reporter:Ce Fu;Tong-xian Zhang;Cheng-qi Ji;Fa Cheng
Chinese Journal of Polymer Science 2015 Volume 33( Issue 1) pp:14-22
Publication Date(Web):2015 January
DOI:10.1007/s10118-015-1570-x
Twice-painting technique was adopted to prepare heavy-duty anticorrosive coating films formed by aqueous latexes of copolymers of vinylidene chloride (VDC) with an acrylate, namely methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA) or 2-ethylhexyl acrylate (EHA). Harsh salt-spray corrosion tests demonstrated that the optimized twice-painting technique was that the acidic latex solution was adjusted to pH 5–6 for the first painting, while it was utilized directly for the second painting. The test of 600 h of harsh salt-spray corrosion showed that MA-VDC85 coating could protect the steel excellently, whereas the other acrylate-VDC coatings with 75%–90% VDC content could not protect the steel so effectively. Further corrosion test showed that (1) MA-VDC85 coating protected steel from loss of metallic luster for at least 1000 h of salt-spray corrosion; (2) adhesion of MA-VDC85 coating to steel was excellent for at least 800 h of salt-spray corrosion, but became very poor after 1000 h. Differential scanning calorimetry, thermogravimetric analysis, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were used to evaluate the corroded MA-VDC85 film.
Co-reporter:Xing Liu, Hua-Ji Liu, Fa Cheng and Yu Chen
Nanoscale 2014 vol. 6(Issue 13) pp:7453-7460
Publication Date(Web):11 Apr 2014
DOI:10.1039/C4NR00739E
Oxidized graphene sheets (OGS) were treated with a hyperbranched polyethylenimine (PEI) under hydrothermal conditions to generate nanocomposites of graphene quantum dots (GQDs) functionalized with PEI (GQD–PEIs). The influence of the reaction temperature and the PEI/OGS feed ratio on the photoluminescence properties of the GQD–PEIs was studied. The obtained GQD–PEIs were characterized by TEM, dynamic light scattering, elemental analysis, FTIR, zeta potential measurements and 1H NMR spectroscopy, from which their structural information was inferred. Subsequently, isobutyric amide (IBAm) groups were attached to the GQD–PEIs through the amidation reaction of isobutyric anhydride with the PEI moieties, which resulted in GQD–PEI–IBAm nanocomposites. GQD–PEI–IBAm was not only thermoresponsive, but also responded to other stimuli, including inorganic salts, pH, and loaded organic guests. The cloud point temperature (Tcp) of aqueous solutions of GQD–PEI–IBAm could be modulated through changing the number of IBAm units in GQD–PEI–IBAm, by varying the type and concentration of the inorganic salts and loaded organic guests, or by varying the pH. All the obtained GQD–PEI–IBAm nanocomposites were photoluminescent, and their maximum emission wavelengths were not influenced by outside stimuli. Their emission intensities were influenced a little or negligibly by pH, traditional salting-out anions (Cl− and SO42−), and the relatively polar aspirin guest. However, the traditional salting-in I− anion and the more hydrophobic 1-pyrenebutyric acid (PBA) guest could effectively quench their fluorescence. 2D NOESY 1H NMR spectra verified that GQD–PEI–IBAm accommodated the relatively polar aspirin guest using the PEI–IBAm shell, but adsorbed the relatively hydrophobic PBA guest through the nanographene core. The release rate of the guest encapsulated by the thermoresponsive GQD is different below and above Tcp.
Co-reporter:Rui-Cong Wang, Hua-Ji Liu, Jin-Ge Tong and Yu Chen
Polymer Chemistry 2014 vol. 5(Issue 7) pp:2417-2424
Publication Date(Web):16 Dec 2013
DOI:10.1039/C3PY01388J
Three amino acid derivatives, GI, AI and VI resulted from the corresponding isobutyryl chloride modified Gly, Ala and Val, were each conjugated with some of the hydroxyl groups of poly(vinyl alcohol) (PVA) through a one-step esterification reaction, resulting in PVA-GI, PVA-AI and PVA-VI, respectively. FTIR and 1H NMR verified the successful conjugation of these amino-acid derivative units onto PVA. X-ray diffraction characterization demonstrated that the introduction of these units led to a decrease in the degree of crystallinity. Turbidity measurement showed that GI, AI and VI were all effective molecular units to make such PVA-derivatives thermoresponsive, and the phase transition temperature could be modulated in a wide range by varying the degree of substitution or altering the type of amino-acid derivative. The efficiency of these three molecular units to make PVA thermoresponsive was as follows: VI > AI ∼ GI. Dynamic light scattering (DLS) measurement demonstrated that these thermoresponsive PVA derivatives experienced a conformation transition from the loose coil to the compact and crumbled state, till the aggregated state was attained following the temperature increase. Such thermoresponsive PVA derivatives were good dispersing agents for colloidal gold nanoparticles (AuNPs) in water when enough polymers were used. A core–shell structure was proved by DLS and TEM measurements where the AuNP was covered by a thick organic shell formed by the thermoresponsive PVA derivatives. Turbidity measurement showed that the composites of such PVA derivatives and AuNPs were also thermoresponsive, and they had a little lower phase transition temperature than those of the corresponding neat thermoresponsive PVA derivatives. DLS measurement demonstrated that such thermoresponsive AuNP composites experienced a shell shrinkage and subsequent aggregation of nanoparticles during the temperature increase. Moreover, AuNPs stabilized by such thermoresponsive PVA derivatives showed better salt-resistance than those stabilized by neat PVAs.
Co-reporter:Ce Fu;Hong-Wei Qin;Hai-Jie Ben;Jing Han;Wen-Zhu Cui;Fa Cheng
Journal of Applied Polymer Science 2014 Volume 131( Issue 8) pp:
Publication Date(Web):
DOI:10.1002/app.40192
Abstract
A series of aqueous latexes with solid contents of 56%–59% were synthesized by binary emulsion copolymerization of vinylidene chloride (VDC) with an acrylate, namely methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), hexyl acrylate (HA), or 2-ethylhexyl acrylate (EHA). Differential scanning calorimetry (DSC) and Fourier-transform infrared (FTIR) spectroscopy showed that the acrylate units with short ester side-chains, such as MA and EA, made the copolymers hard and the crystallization tendency of their PVDC segments was reduced. Hydrophobic acrylates with relatively long ester groups, such as HA and EHA, gave flexible copolymers, and favored the crystallization of their PVDC segments. BA endowed the copolymers with medium flexibility and crystallization tendency. As coating materials, the copolymers bearing MA and EA adhered poorly to the tinplate before or after 100 hr of salt-spray corrosion, whereas those bearing BA, HA, or EHA showed good adhesion to tinplate when they had little or no crystallinity. After 100 hr of salt-spray corrosion, only BA–VDC80, containing 80% VDC, retained both excellent adhesion to metal and excellent barrier performance. Further study demonstrated that BA–VDC80 could protect tinplate from rusting for at least 250 hr under harsh salt-spray corrosion. Scanning electron microscopy, FTIR-attenuated total reflectance spectroscopy and DSC were used to evaluate the corroded BA–VDC80 film. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40192.
Co-reporter:Bin Wang, Hua-Ji Liu, Ting-Ting Jiang, Qi-Heng Li, Yu Chen
Polymer 2014 Volume 55(Issue 23) pp:6036-6043
Publication Date(Web):5 November 2014
DOI:10.1016/j.polymer.2014.09.051
•Thermo-, and pH dual-responsive PVIm copolymers were successfully prepared.•Distribution of IMMA units along the PVIm chain had marked influence on Tcp.•Such copolymers could be used as smart organocatalysts in the hydrolysis of NPA.A monomer, 2-(isobutyramido)-3-methylbutyl methacrylate (IMMA) was synthesized through a two-step reaction. When a few of IMMA (less than 4 mol%) was copolymerized with N-vinylimidazole (VIm) under free radical polymerization condition, water-soluble P(VIm-co-IMMA) copolymers were obtained. Their structural information was verified and interpreted from 1H NMR, FTIR and GPC. Kinetic analyses from 1H NMR demonstrated that one-batch addition of IMMA into the polymerization system led to an inhomogeneous distribution of IMMA units in the copolymers, whereas homogeneous distribution of IMMA units in the copolymers could be obtained through the portion-wise addition of IMMA monomer. The thermal properties of such copolymers were measured by DSC. Compared with PVIm homopolymer, the few IMMA units in the P(VIm-co-IMMA) copolymer had little influence on the Tg values. The obtained P(VIm-co-IMMA) copolymers were thermoresponsive in water, and their phase transition temperatures could be efficiently raised through reducing the IMMA content in the copolymers, raising the addition times of IMMA monomers or lowering the pH of media. Dynamic light scattering analysis showed that unlike the traditional thermoresponsive linear polymers, obvious size shrinkage around the phase transition temperature could not be observed in such P(VIm-co-IMMA) copolymers. Such copolymers could be used as smart organocatalysts in the hydrolysis of p-nitrophenyl acetate. Below the phase transition temperature the reaction rate followed the Arrhenius law, but above the phase transition temperature the reaction rate increased much slower than the prediction from the Arrhenius law. Moreover, the catalytic transition temperature could be tuned through utilizing the P(VIm-co-IMMA) copolymers with different phase transition temperature. The mechanism was discussed accordingly.
Co-reporter:Hong-wei Qin;Hua-ji Liu 陈宇
Chinese Journal of Polymer Science 2014 Volume 32( Issue 10) pp:1338-1347
Publication Date(Web):2014 October
DOI:10.1007/s10118-014-1509-7
Acetamide (C2), propionamide (C3), butyramide (C4), isobutyramide (i-C4), isovaleramide (i-C5) and trimethylacetamide (t-C5) groups each were introduced to the terminals of hyperbranched polyethylenimine (HPEI) through the amidation reaction between HPEI and the corresponding anhydride. Moreover, HPEIs terminated with two kinds of amides were also prepared. The first amide was fixed to be i-C4 with 52% degree of amidation (DA), and the second amide varied from C2, C3, C4, i-C5 to t-C5. All the polymers were characterized by 1H-NMR. Turbidimetry measurements were performed for these polymers in water at different temperatures. With respect to the polymers bearing only one kind of amide group, except C2, all the other amide groups could render thermoresponsive properties to HPEI. The specific ordering of these amide groups to reduce the cloud point temperature (Tcp) was as follows: i-C5 > t-C5 > C4 > i-C4 > C3. Moreover, the more branched i-C4 and t-C5 were better groups than their less branched isomers C4 and i-C5 in the Tcp range of 12–51 °C to render the sharper phase transition to the thermoresponsive polymers. As for the polymers bearing two kinds of amide groups, the further introduction of C2, C3, C4, i-C5 or t-C5 could effectively endow HPEI bearing 52% of i-C4 with thermoresponsive properties. The specific ordering of these second amide groups to reduce the Tcp was as follows: i-C5 > C4 > i-C4 > C3 > C2. C4, i-C5 and t-C5 were all effective second amide groups to prepare the thermoresponsive polymers with sharper phase transition.
Co-reporter:Hua-ji Liu;Run-hua Dong 陈宇
Chinese Journal of Polymer Science 2014 Volume 32( Issue 7) pp:961-968
Publication Date(Web):2014 July
DOI:10.1007/s10118-014-1471-4
Certain amount of primary amine (NH2) groups of hyperbranched polyethylenimine (HPEI) was first protected by Boc groups. Subsequently, the residual reactive amine groups were reacted with isobutyric anhydride to introduce isobutyramide (IBAm) groups to HPEI. Finally, Boc groups were deprotected to result in HPEI-IBAm-NH2 with 18% of primary amine terminals on the periphery and 80% of IBAm terminal groups (abbreviated as HPEI-IBAm0.80-NH2). 1H-NMR characterization proved the successful preparation of the product in each step. Compared with its spatial isomer HPEIIBAm0.80 without primary amine groups, 1H-NMR spectra verified that more IBAm groups were located in the interior of HPEI-IBAm0.80-NH2. The further modification of HPEI-IBAm0.80-NH2 and HPEI-IBAm0.80 with p-nitrobenzaldehyde demonstrated that HPEI-IBAm0.80-NH2 was more reactive than HPEI-IBAm0.80 due to its possession of primary amines. Turbidimetry measurements showed that HPEI-IBAm0.80-NH2 was thermoresponsive in water. In the pH range of 9.5–10 its cloud point temperature (Tcp) was constant, and it increased obviously upon decreasing the pH below 9.5. The thermoresponsive HPEI-IBAm0.8 exhibited the similar trend, but the pH threshold to achieve the constant Tcp was around 8.5. Moreover, HPEI-IBAm0.8-NH2 showed higher Tcp and broader phase transition than HPEI-IBAm0.8. The mechanism leading to the different thermoresponsive properties between HPEI-IBAm0.8-NH2 and its spatial isomer HPEI-IBAm0.8 was discussed.
Co-reporter:Man-Ling Wang, Ting-Ting Jiang, Yang Lu, Hua-Ji Liu and Yu Chen
Journal of Materials Chemistry A 2013 vol. 1(Issue 19) pp:5923-5933
Publication Date(Web):12 Mar 2013
DOI:10.1039/C3TA10293A
Hyperbranched polyethylenimine (HPEI) modified polyacrylonitrile fiber (PANF) was prepared through a water mediated hydrolysis and amidation reaction in an autoclave. The grafting amount of HPEI onto PANF could be modulated conveniently by varying the preparation conditions, such as reaction temperature, reaction time and the feed ratio of HPEI to PANF. The Young's modulus of the PANF decreased with the grafting of HPEI, especially when more HPEIs were grafted. As for the PANF-g-HPEI with low HPEI content, the Young's moduli were similar before and after loading of AuNPs, whereas the loading of AuNPs obviously deteriorated the strength of the fibers with high HPEI content. From the nitrogen adsorption and desorption isotherms, it could be seen that PANF contained nanometer sized pores, and the grafting with HPEI did not affect the pore size, but did reduce the surface area. Moreover, the loading of AuNPs into PANF-g-HPEI also did not influence the pore size, but decreased the surface area. FTIR and XPS analyses demonstrated that the obtained PANF-g-HPEI not only contained a large amount of amino groups from the HPEI moiety, but also many carboxylate ions due to the hydrolysis of the cyano groups of PANF. XRD characterization proved that the inner crystal region of PANF was partially broken by the introduction of HPEI moieties. SEM showed that the PANFs swelled up after grafting with HPEI, and the increase of the grafting efficiency led to a larger average diameter of the fibers. When the grafting amount of HPEI onto PANF reached as high as 97%, the surface of the fibers was severely impaired. The obtained PANF-g-HPEIs could be successfully used as supporters and stabilizers in the preparation of small-sized AuNPs. TEM characterization showed that the mixing time of PANF-g-HPEIs with HAuCl4 aqueous solution affected the size and size distribution of the formed AuNPs, and the optimal mixing time was around 0.5 h. The average diameter of the obtained AuNPs was around 3.0 nm at a feed ratio of amino groups of PANF-g-HPEI to Au atoms ([N]:[Au]) of 200, independent of HPEI content of the PANF-g-HPEIs used. Reducing the [N]:[Au] feed ratio increased the average size of the obtained AuNPs. The AuNPs supported by PANF-g-HPEIs could be used as efficient catalysts for the heterogeneous catalytic reduction of 4-nitrophenol by NaBH4. The PANF-g-HPEI with lower HPEI content endowed the supported AuNPs with a slightly higher catalytic rate. These heterogeneous AuNP catalysts could be conveniently recovered and reused many times, especially the AuNPs supported by the PANF-g-HPEIs containing a low content of HPEI. The turnover number (TON) values of the AuNPs supported by PANF-g-HPEI0.31 and PANF-g-HPEI0.58 could reach more than 5 × 104, which is unprecedented in the catalytic reduction of 4-nitrophenol.
Co-reporter:Jing-Yuan Yin, Hua-Ji Liu, Songzi Jiang, Yu Chen, and Yefeng Yao
ACS Macro Letters 2013 Volume 2(Issue 11) pp:1033
Publication Date(Web):November 8, 2013
DOI:10.1021/mz400474v
The pyrolysis of a hyperbranched polyethylenimine (PEI) and glycerol mixture under microwaves generated the carbon dot (CD) functionalized with PEI (CD-PEI). Isobutyric amide (IBAm) groups were attached to CD-PEI through the amidation reaction of isobutyric anhydride and the PEI moiety, which resulted in the thermoresponsive CD-PEI-IBAm’s. CD-PEI-IBAm’s were not only thermoresponsive but also responded to other stimuli, including inorganic salt, pH, and loaded organic guests. The cloud point temperature (Tcp) of the aqueous solutions of CD-PEI-IBAm’s could be modulated in a broad range through changing the number of IBAm units of CD-PEI-IBAm or varying the type and concentration of the inorganic salts, pH, and loaded organic guests. All the obtained CD-PEI-IBAm’s were photoluminescent, which could be influenced a little or negligibly by the added salts, pH, and the organic guests encapsulated.
Co-reporter:Jing Zhang, Hua-Ji Liu, Yuan Yuan, Songzi Jiang, Yefeng Yao, and Yu Chen
ACS Macro Letters 2013 Volume 2(Issue 1) pp:67
Publication Date(Web):December 28, 2012
DOI:10.1021/mz300613q
Hyperbranched polyethylenimine terminated with isobutyramide groups (HPEI-IBAm) was mixed with 4-(phenylazo)benzoic acid (PABA) to form supramolecular complexes through the neutralization reaction between the amino groups of HPEI-IBAm and the carboxylic acid group of PABA, which was verified by 1H and 2D NOESY 1H NMR spectroscopy. The obtained supramolecular complexes with a molar ratio of PABA to HPEI-IBAm of ≤8 were soluble in water and exhibited thermoresponsive properties. Their cloud point temperature (Tcp) was sensitive to PABA content, and PABA molecules were exchanged between HPEI-IBAm hosts. The topology of the polymer affected the change in Tcp of the complexes. At pH ∼7, increasing the PABA content decreased Tcp, whereas it caused Tcp to increase at pH ∼9. Reversible trans-to-cis photoisomerization of azobenzene units in the complexes occurred following irradiation with UV or visible light. At pH ∼7, trans-to-cis isomerization of azobenzene units increased Tcp, whereas the opposite occurred at pH ∼9.
Co-reporter:Qiang Tang;Fa Cheng;Jin Cui 陈宇
Chinese Journal of Polymer Science 2013 Volume 31( Issue 7) pp:1046-1055
Publication Date(Web):2013 July
DOI:10.1007/s10118-013-1298-4
Multiarm star block copolymers hyperbranched polyethylenimine-b-poly(2-hydroxyethyl methacrylate) (HPEI-b-PHEMA) with average 28 PHEMA arms have been prepared by atom transfer radical polymerization (ATRP) of HEMA in a mixed solvent of methanol and water using a core-first strategy. The hyperbranched macroinitiator employed was prepared on the basis of well-defined hyperbranched polyethylenimine with Mw/Mn of 1.04 by amidation with 2-bromo-isobutyryl bromide. The polymerization condition was optimized to prepare star copolymers with narrow dispersity, and the variables included the volume ratio of methanol to water, the molar ratio of initiating site to CuCl and the molar ratio of [CuCl]:[CuBr2]. Under the optimized polymerization condition, the lowest Mw/Mn value of the obtained star copolymers was around 1.3. Kinetic analysis showed that an induction period existed in the polymerization of HEMA. After this induction period, a linear dependence of ln([M]0/[M]t) on time was observed. The obtained HPEI-b-PHEMA could adsorb hydrophilic molecules. The comparison with the star copolymer with hydrophobic core and hydrophilic PHEMA shell verified that both the hydrophilic core and shell could host the hydrophilic guests, but the amidated HPEI core was more effective than the PHEMA shell.
Co-reporter:Xu-Ran Mu, Jin-Ge Tong, Yi Liu, Xun-Yong Liu, Hua-Ji Liu, Yu Chen
Polymer 2013 Volume 54(Issue 9) pp:2341-2346
Publication Date(Web):19 April 2013
DOI:10.1016/j.polymer.2013.03.004
The influence of aliphatic acids on the phase transition temperature of thermoresponsive hyperbranched polyethylenimine possessing a large amount of isobutyramide and amine groups (HPEI-IBAm) was studied systematically. Nine saturated aliphatic acids including formic acid (C1), acetic acid (C2), n-pentanoic acid (n-C5), trimethylacetic acid (t-C5), hexanoic acid (C6), octanoic acid (C8), decanoic acid (C10), dodecanoic acid (C12) and hexadecanoic acid (C16) were used to measure their effects on the cloud point temperature (Tcp) of HPEI-IBAm in a mixture of H2O/DMF (v/v = 9:1). For comparison, the effect of these aliphatic acids on the traditional thermoresponsive linear poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and poly(N-isopropyl acrylamide) (PNIPAm) was also studied. The influence of aliphatic acids on different thermoresponsive polymers was different. The aliphatic acids with shorter carbon chains (C ≤ 8) increased the Tcp of HPEI-IBAm, and those with long hydrocarbon chains (C > 8) depressed the Tcp. Moreover, the effect of aliphatic acids with C ≤ 5 was similar, even though their configurations might be different. The specific ranking of aliphatic acids in raising the Tcp of HPEI-IBAm was as follows: C1 ～ C2 ～ n-C5 ～ t-C5 > C6 > C8 > C10 > C12 ～ C16. With respect of the linear PDMAEMA, all the aliphatic acids employed elevated its Tcp. The specific ranking of aliphatic acids in raising the Tcp of linear PDMAEMA was similar to that for dendritic HPEI-IBAm, but with a minor difference: C1 ～ C2 ～ n-C5 ～ t-C5 > C6 > C8 > C10 > C12 > C16. In the case of the linear PNIPAM, the aliphatic acids with C ≤ 6 had almost no influence on the Tcp. Raising the carbon number to be 8 or higher leads to the obvious Tcp depression. The different effect of aliphatic acids on the phase transition of these thermoresponsive polymers was discussed, and it was mainly attributed to their structural and topological difference.
Co-reporter:Songzi Jiang, Yefeng Yao, Qun Chen, and Yu Chen
Macromolecules 2013 Volume 46(Issue 24) pp:9688-9697
Publication Date(Web):December 3, 2013
DOI:10.1021/ma402095w
High-resolution 1H NMR has been used on the thermoresponsive hyperbranched polyethylenimines (HPEIs) modified with isobutyramide (IBAm) groups (HPEI-IBAm), to study the structure and dynamics of the macromolecules in aqueous solution before and after the phase transition. It shows that the HPEI-IBAm macromolecule having a high IBAm substitution degree has a clear phase transition in aqueous solution, whereas the HPEI-IBAm macromolecule having a low IBAm substitution degree does not. The different phase transition behaviors have been attributed to the content as well as the distribution of the IBAm groups in the macromolecules. In order to deepen the understanding of the phase transition, the hydrophobic–hydrophobic interaction inside the HPEI-IBAm macromolecules was investigated by monitoring the 1H–1H NOEs between the different hydrophobic groups. An enhanced hydrophobic–hydrophobic interaction was observed in the HPEI-IBAm macromolecule having a high IBAm substitution degree after the phase transition, which provides a new perspective for our understanding of the phase transition of the macromolecules in aqueous solution. By using PFG diffusion NMR, the weight distributions of the moving particles in the solution were monitored. The β parameter used in the PFG diffusion NMR, which reflects the change of the weight distributions of the moving particles in solution, has proved to be a good way to monitor the aggregation process of the moving particles in the solution.
Co-reporter:Yi Liu, You Fan, Yuan Yuan, Yu Chen, Fa Cheng and Shi-Chun Jiang
Journal of Materials Chemistry A 2012 vol. 22(Issue 39) pp:21173-21182
Publication Date(Web):22 Aug 2012
DOI:10.1039/C2JM34445A
A series of organo-soluble gold nanoparticles (AuNPs) were prepared through the reduction of HAuCl4 by NaBH4 in the presence of amphiphilic hyperbranched copolymers bearing a hydrophilic hyperbranched polyethylenimine (PEI) core and a hydrophobic dendritic shell. For comparison, the corresponding analogues with a PEI core and a linear shell were also used to prepare the organo-soluble AuNPs. All the obtained AuNPs were characterized by transmission electron microscopy. It was found that under a high feed ratio of polymer to HAuCl4, the average diameter of the obtained small AuNPs was similar, and was independent of the shell morphology of the hyperbranched polymeric stabilizers. Reducing the feed ratio of polymer to HAuCl4 led to the formation of larger AuNPs and irregularly shaped AuNP aggregates. The stability evaluation on the basis of two-month shelf-storage demonstrated that the obtained AuNPs were stable under shelf-storage regardless of whether the shell of the hyperbranched polymeric stabilizer was dendritic or linear. These organo-soluble AuNPs could be used as efficient catalysts for the biphasic catalytic reduction of 4-nitrophenol by NaBH4, and could also be conveniently recovered and reused. The stabilizers with a dendritic shell endowed the AuNP catalyst with a higher performance than the corresponding stabilizers with a linear shell, including: (1) a higher catalytic rate; (2) the ability to be recovered and reused more times; (3) a maximal turnover number of around 23000, which is unprecedented in the catalytic reduction of 4-nitrophenol.
Co-reporter:Lin Li, Man-Ling Wang, Yu Chen, Shi-Chun Jiang
Journal of Colloid and Interface Science 2012 Volume 387(Issue 1) pp:146-152
Publication Date(Web):1 December 2012
DOI:10.1016/j.jcis.2012.08.009
The terminal hydroxyl groups of amphiphilic multiarm star copolymers with a hydrophilic hyperbranched polyethylenimine (PEI) core and hydrophobic poly(ε-caprolactone) (PCL) arms were partially or completely transformed into the radical-crosslinkable methacrylate (MA) groups (PEI-b-PCL-MA). The resulting PEI-b-PCL-MA polymers with 100% MA substitution self-assembled in water into simple vesicles, whereas those with partial MA substitution aggregated into complex vesicles. These structures could be proved by transmission electron microscopy and dynamic light scattering only after crosslinking the intra-vesicular MA groups that generated the covalently stabilized vesicles (CSVs). The obtained CSVs could be used as host for the formation of gold nanoparticle (AuNP) cluster, and the AuNP clusters stabilized by the CSVs were stable under a wider range of CSV/AuNP feed ratio than those stabilized by the uncrosslinked precursors. The diameter of AuNPs in the clusters was in the range of 4–6 nm, and the distance of adjacent AuNPs could be modulated through altering the feed ratio of CSV/AuNP. The color of the solutions of AuNPs with CSV could be tuned from brown to red, purple, even blue. The composites of CSV and AuNPs could be further used as nanocarriers to accommodate hydrophobic guest of pyrene, and a higher amount of AuNPs in the nanocarriers led to a lower encapsulation capacity for pyrene guests.Graphical abstractHighlights► Covalently stabilized vesicle (CSV) templates the formation of AuNP cluster. ► The distance of AuNPs in the cluster could be tuned. ► The color of solution of composite of AuNPs and CSV could be tuned. ► The composite of AuNPs and CSV could further encapsulate hydrophobic guest.
Co-reporter:Peng-Fei Cao;Rong-Xu Zhao;Lin Li;Wen-Wen Yang;Fa Cheng;Cong-Hua Lu;Shi-Chun Jiang
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 2) pp:227-236
Publication Date(Web):
DOI:10.1002/pola.25015
Abstract
The large amount of terminal hydroxyl groups of amphiphilic multiarm star copolymers with hyperbranched polyethylenimine (PEI) as the hydrophilic core and poly(ε-caprolactone) (PCL) arms as the hydrophobic shell were completely transformed into the radical-crosslinkable methacrylate (MA) groups. The resulting PEI-b-PCL-MA polymers could self-assemble into vesicles in water, which was verified by dynamic light scattering (DLS) and transmission electron microscopy (TEM). After crosslinking the intravesicular MA groups, covalently stabilized vesicles (CSVs) were generated. These CSVs were further characterized by DLS and TEM, and it was found that the corona of the vesicles was not the simple double-layer structure, but contained a certain amount of PEI-b-PCL unimolecular micellar units between the double-layer. These CSVs could accommodate both apolar and polar guests using their hydrophobic PCL zones and void cores, respectively. Moreover, these CSVs showed superior capacities for apolar guests to their noncrosslinked precursors and the corresponding traditional amphiphilic multishell star polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Co-reporter:Chun-Xiao Zhang, Bin Wang, Yu Chen, Fa Cheng, Shi-Chun Jiang
Polymer 2012 Volume 53(Issue 18) pp:3900-3909
Publication Date(Web):17 August 2012
DOI:10.1016/j.polymer.2012.07.002
The Sn(Oct)2 catalyzed polymerization condition of l-lactide (LLA) and racemic lactide (r-LA) using hyperbranched polyethylenimine (PEI) as the macroinitiator was optimized. Multiarm star polymers bearing PEI core and well-controlled poly(l-lactide) (PLLA) or poly(racemic lactide) (PDLLA) arms were successfully prepared under the optimized condition, including: (1) high concentration of Sn(Oct)2 catalyst was required; (2) with respect to the polymerization of r-LA, the optimal temperature was in the range of 115–130 °C; (3) as for the polymerization of LLA, the optimal temperature was only around 130 °C. Model experiments demonstrated that secondary amine could also effectively initiate the Sn(Oct)2 catalyzed polymerization of LA under the optimized condition, however, its initiation efficiency was usually a little less than 100%, unlike the primary amine and hydroxyl initiators. The results of Gel Permeation Chromatography demonstrated that the obtained multiarm star polymers with PDLLA arms had narrower dispersities than those with PLLA arms. Thermal analyses demonstrated that raising the arm numbers of the stars impaired their thermal stability a little. Stars with PDLLA arm were amorphous. The glass transition temperature of all the PDLLA-based polymers was similar and had no obvious relationship with the arm length, arm number and the molecular architecture. The crystallizability of star polymers with PLLA arm was weaker than that of linear PLLA, and only star polymers with long PLLA arm showed obvious crystallization. The guest encapsulation and release properties of the obtained star polymers were also investigated. It was found that their guest encapsulation capacity had correlation with the PLA arm length, the PEI core size and the degree of quaternization of PEI core, but had no relationship with the type of the PLA arm (PDLLA or PLLA). Whereas the guest release rate was strongly affected by the arm type.Graphical abstract
Co-reporter:Fang Yuan, Hong Pan, Fa Cheng, Yu Chen, Shi-Chun Jiang
Polymer 2012 Volume 53(Issue 11) pp:2175-2182
Publication Date(Web):9 May 2012
DOI:10.1016/j.polymer.2012.03.043
Ethyl cellulose (EC), lactide (LA) and branching comonomer 2,2-bis(hydroxymethyl) butyric acid (BHB) were copolymerized in xylene using Sn(Oct)2 as catalyst. Catalyst amount and polymerization temperature were optimized for the effective introduction of certain amount of branched polylactide (PLA) into the side chains of comb-like copolymers having EC backbone. The characterization of the obtained copolymers by GPC and 1H NMR demonstrated that the influence of polymerization temperature in the range of 110–150 °C on the efficient incorporation of branching units was not pronounced, whereas high amount of catalyst was the key point. The content of branching units in the copolymers could be enhanced by increasing the feed amount of BHB monomer. A plausible mechanism for the polymerization was proposed according to the model experiments. Compared with the comb-like copolymers with merely linear PLA side chains, the ones bearing both branched and linear PLA side chains had the following characters: (1) better solubility in the polar solvent of ethanol; (2) much faster hydrolysis degradation. These characters became more pronounced when the content of branching units in the side chains increased.
Co-reporter:De-Yu Zhu, Fa Cheng, Yu Chen, Shi-Chun Jiang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2012 Volume 397() pp:1-7
Publication Date(Web):5 March 2012
DOI:10.1016/j.colsurfa.2012.01.006
Four sulfonate-containing gemini surfactants, C7–M0–C7, C7–M1–C7, C7–M2–C7 and C11–M1–C11, with long rigid or semi-rigid spacer have been synthesized. Fully rigid spacer of C7–M0–C7 is composed two rigid benzene rings and two rigid carbonyl groups. Besides the rigid moieties as C7–M0–C7, the spacers of C7–M1–C7, C7–M2–C7 and C11–M1–C11 contain one or two flexible methylene units. The characterization by 1H NMR, 13C NMR, electrospray ionization/mass spectrometry (ESI-MS) and Fourier transform infrared (FT-IR) verified the structural characters of these new gemini surfactants. The basic surface properties of these novel gemini surfactants were investigated through measuring the relationship between the surface tension of water and the surfactant concentration, and compared with those of the conventional single-chain surfactant sodium dodecylbenzenesulfonate (SDSB). The curves of surface tension versus logarithm of concentration of C7–Mx–C7 surfactants were unlike the traditional plot exemplified by SDBS. Above the critical micelle concentration (cmc), the surface tension of aqueous solutions of C7–Mx–C7 did not become steady, but still obviously decreased with the concentration increase, which was supposed to be related with the long rigid or semi-rigid spacers. All these gemini surfactants showed lower cmc and C20 (surfactant concentration required for lowering the surface tension of water by 20 mN/m) values, but higher γcmc (surface tension at cmc) value than SDBS. The gemini surfactants with semi-rigid spacers exhibited superior surface activity to that with fully rigid spacer. The aggregation behavior of C7–Mx–C7 in water was investigated using dynamic light scattering (DLS) and transmission electron microscopy (TEM). It was found that the gemini surfactants with long fully rigid spacer preferred to form vesicles, whereas the ones with semi-rigid spacers self-assembled into the mixture of micelles and vesicles at low surfactant concentration and formed vesicles at high surfactant concentration.Graphical abstractHighlights► Gemini surfactants (Cy–Mx–Cy) with long rigid or semi-rigid spacers were synthesized. ► Cy–Mx–Cy had superior surface activities to the single chain SDBS surfactant. ► The curves of γ versus log[Cy–Mx–Cy] were different from that of the traditional SDBS.
Co-reporter:Xun-Yong Liu, Xu-Ran Mu, Yi Liu, Hua-Ji Liu, Yu Chen, Fa Cheng, and Shi-Chun Jiang
Langmuir 2012 Volume 28(Issue 10) pp:4867-4876
Publication Date(Web):February 22, 2012
DOI:10.1021/la300046w
The salt effects on the water solubility of thermoresponsive hyperbranched polyethylenimine and polyamidoamine possessing large amounts of isobutyramide terminal groups (HPEI-IBAm and HPAMAM-IBAm) were studied systematically. Eight anions with sodium as the counterion and ten cations with chloride as the counterion were used to measure the anion and cation effects on the cloud point temperature (Tcp) of these dendritic polymers in water. It was found that the Tcp of these dendritic polymers was much more sensitive to the addition of salts than that of the traditional thermoresponsive linear polymers. At low anion concentration, the electrostatic interaction between anions and the positively charged groups of these polymers was dominant, resulting in the unusual anion effect on the Tcp of these polymers in water, including (1) Tcp of these dendritic polymers decreasing nonlinearly with the increase of kosmotropic anion concentration; (2) the chaotropic anions showing abnormal salting-out property at low salt concentration and the stronger chaotropes having much pronounced salting-out ability; (3) anti-Hofmeister ordering at low salt concentration. At moderate to high salt concentration, the specific ranking of these anions in reducing the Tcp of HPEI-IBAm and HPAMAM-IBAm polymers was PO43– > CO32– > SO42– > S2O32– > F– > Cl– > Br– > I–, in accordance with the well-known Hofmeister series. At moderate to high salt concentration, the specific ranking order of inorganic cations in reducing the Tcp of HPEI-IBAm polymer was Sr2+ ≈ Ba2+ > Na+ ≈ K+ ≈ Rb+ > Cs+ > NH4+ ≈ Ca2+ > Li+ ≈ Mg2+. This sequence was only partially similar to the typical Hofmeister cation series, whereas at low salt concentration the cation effect on Tcp of the dendritic polymer was insignificant and no obvious specific ranking order could be found.
Co-reporter:Rong-Xu Zhao, Lin Li, Bin Wang, Wen-Wen Yang, Yu Chen, Xue-Hao He, Fa Cheng, Shi-Chun Jiang
Polymer 2012 Volume 53(Issue 3) pp:719-727
Publication Date(Web):2 February 2012
DOI:10.1016/j.polymer.2011.12.045
Co-reporter:Yi Liu;Xun-Yong Liu;Hua-Ji Liu;Fa Cheng
Macromolecular Research 2012 Volume 20( Issue 6) pp:578-584
Publication Date(Web):2012 June
DOI:10.1007/s13233-012-0079-1
Hyperbranched polyamidoamine (HPAMAM) polymers, chemically analogous to the commercially available PAMAM dendrimer, were modified with isobutyric anhydride to result in isobutyramide (IBAm) terminated HPAMAMs (HPAMAM-IBAm). The aqueous solutions of HPAMAM-IBAm polymers had the lower critical solution temperature (LCST). The lower molecular-weight HPAMAM-IBAm exhibited higher LCST and the LCST difference was around 18 °C for one pseudo-generation variation. Further, the hyperbranched thermoresponsive polymers exhibited much lower LCSTs than the corresponding dendrimers with similar molecular weight. The LCST of HPAMAM-IBAm was pH sensitive. At pH below 10, the LCST increased significantly upon decreasing the pH, whereas, at pH above 10, the LCST decreased slowly with an increasing pH value. Nine sodium salts were used to measure the anion effect on the LCST of HPAMAM-IBAm. It was found that the LCST could also be modulated up or down in a broad range by simply adding a small amount of different kinds of inorganic anions. The specific ranking of inorganic anions in salting-out HPAMAM4-IBAm polymer was in accordance with the well-known Hofmeister series.
Co-reporter:Zhan-Long Yu;Fa Cheng;Shao-Jing Zhao;Jian-Wei Zhang
Macromolecular Research 2011 Volume 19( Issue 2) pp:189-196
Publication Date(Web):2011 February
DOI:10.1007/s13233-011-0201-9
Conventional surfactant dodecylbenzenesulfonic acid (DBSA) and its corresponding Gemini surfactant acid (GSA) were simply mixed with a solution of hyperbranched polyethylenimine (HPEI) in chloroform. This resulted in the novel supramolecular complexes, HPEI-DBSA and HPEI-GSA, through a neutralization reaction between the amino groups of HPEI and the sulfonic-acid groups of DBSA and GSA. The formed supramolecular complexes and their precursors were characterized by FTIR, 1H NMR, and dynamic light scattering. HPEI-DBSA and HPEI-GSA exhibited inverted-micelle properties that could accommodate the water-soluble guest molecules in an apolar solvent. With the anionic dye methyl orange (MO) as the model guest, both HPEI-DBSA and HPEI-GSA showed superior guest-encapsulation performance than the supramolecular nanocarrier derived from the assembly of aliphatic acid onto HPEI. For example, HPEI-DBSA and HPEI-GSA nanocarriers could encapsulate more MO molecules, and a much smaller amount of the surfactant molecules was required to achieve the maximum MO encapsulation. These results highlight the importance of strong-acid groups of the surfactants in raising the guest-encapsulation efficiency of this type of supramolecular nanocarrier. HPEI-DBSA and HPEI-GSA had different guestencapsulation mechanisms. This indicates that HPEI-GSA can encapsulate basic guests more than HPEI-DBSA, such as MO and fluorescein sodium (FS), but fewer relatively acidic guests, such as Alizarin Yellow R sodium salt and bromophenol blue.
Co-reporter:Nan Hu;Jing-Yuan Yin;Qiang Tang
Journal of Polymer Science Part A: Polymer Chemistry 2011 Volume 49( Issue 17) pp:3826-3834
Publication Date(Web):
DOI:10.1002/pola.24818
Abstract
A series of organo-soluble spherical gold nanoparticles (AuNPs) were prepared through the reduction of HAuCl4 by NaBH4 in the presence of amphiphilic hyperbranched polymers that had a hydrophilic hyperbranched polyethylenimine core and a hydrophobic shell formed by many palmitamide (C16) chains. For comparison, the corresponding linear polymeric analog derived from linear polyethylenimine was also used to prepare the organo-soluble AuNPs. The obtained AuNPs were characterized by transmission electron microscopy. It was found that higher feed ratio of polymer to HAuCl4 and utilization of polymers with higher C16 density usually resulted in smaller AuNPs with relatively lower polydispersity. Except of the polymer having the pronounced low molecular weight, the molecular weight and the morphology of the amphiphilic polymers had almost no obvious effect on the size of the formed AuNPs. These organo-soluble AuNPs could be used as efficient catalysts for the biphasic catalytic reduction of 4-nitrophenol by NaBH4. Their apparent rate coefficients had correlation with the molecular weight of the used amphiphilic polymers, but were less relevant to the morphology of these polymers. These organo-soluble AuNPs could be conveniently recovered and reused many times. The morphology of the capping polymers had obvious effect on the lifetime of the AuNPs catalysts in the catalytic reduction of 4-nitrophenol. Except of the pronounced low molecular weight hyperbranched polymer, the other hyperbranched ones with relatively high molecular weight rendered the AuNPs to have bigger turnover number values than their linear analog. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Co-reporter:Xun-Yong Liu, Fa Cheng, Yi Liu, Wen-Gang Li, Yu Chen, Hong Pan and Hua-Ji Liu
Journal of Materials Chemistry A 2010 vol. 20(Issue 2) pp:278-284
Publication Date(Web):03 Nov 2009
DOI:10.1039/B916125B
Thermoresponsive gold nanoparticles (AuNPs) with lower critical solution temperature (LCST) adjustable over a broad range were explored to be potentially used as colorimetric sensors. Upon raising the temperature above the LCST the surface plasmon resonance (SPR) peaks of the obtained thermoresponsive AuNPs red-shifted sharply in a narrow temperature range, accompanied by a color transition from transparent red to transparent purple–red until turbid red, which made them suitable to be used as sensitive colorimetric sensors for detecting environmental temperature variation. Moreover, the temperature range of sensitivity of the obtained thermoresponsive AuNPs could be tuned by modulating the molecular weight of core or degree of substitution of the thermoresponsive polymers employed. Furthermore, the solution colors of the thermoresponsive AuNPs were also sensitive to pH and NaCl concentration variation, as a result of which they could also be used as colorimetric sensors for detecting the variation of pH and salt concentration.
Co-reporter:Xun-Yong Liu, Fa Cheng, Yi Liu, Hua-Ji Liu and Yu Chen
Journal of Materials Chemistry A 2010 vol. 20(Issue 2) pp:360-368
Publication Date(Web):06 Nov 2009
DOI:10.1039/B915313F
Novel thermoresponsive gold nanoparticles (AuNPs) with lower critical solution temperature (LCST) were obtained through the non-covalent interaction between a thermoresponsive hyperbranched polyethylenimine with isobutyramide groups (HPEI-IBAm) and citrate-protected AuNPs. The LCSTs of the thermoresponsive AuNPs could be conveniently modulated over a broad range by altering the molecular weight of the HPEI core, the degree of substitution (DS) of the IBAm groups of the HPEI-IBAm polymers or the pH of the solution. The obtained thermoresponsive AuNPs could be used as recyclable responsive catalysts for the reduction reaction of 4-nitrophenol by NaBH4. As far as the thermoresponsive catalysts were concerned, reducing the molecular weight of the HPEI core, lowering the DS values and increasing the concentrations of the capping HPEI-IBAm polymers or the gold resulted in the acceleration of the reaction. By choosing the right capping HPEI-IBAm polymers, the reaction was faster than that catalyzed by AuNPs without capping polymers. The reaction rate was accelerated by elevating the reaction temperature at first, but reached a plateau or decelerated upon raising the temperature close to the LCSTs of the thermoresponsive AuNPs catalysts. Moreover, the obtained thermoresponsive AuNP catalysts could be recovered by heating the temperature above their LCSTs and be recycled at least six times with more than 95% conversion.
Co-reporter:Qiang Tang, Fa Cheng, Xing-Long Lou, Hua-Ji Liu, Yu Chen
Journal of Colloid and Interface Science 2009 Volume 337(Issue 2) pp:485-491
Publication Date(Web):15 September 2009
DOI:10.1016/j.jcis.2009.05.047
Amphiphilic hyperbranched and linear polymers based on the respective palmitic acid modified hyperbranched and linear polyethylenimines have been successfully employed to transfer the citrate-protected 17-nm gold nanoparticles (AuNPs) from water into chloroform without the aid of other compounds. Compared with their corresponding linear analog, the amphiphilic hyperbranched polymers exhibited higher efficiency in transferring the large AuNPs. The chloroform solutions of AuNPs were characterized by UV–vis spectrometry and dynamic light scattering. It was found that aggregated AuNPs existed in the system with the amphiphilic linear polymer as stabilizer, whereas much less aggregated AuNPs could be detected in the system with the amphiphilic hyperbranched polymer as stabilizer. Furthermore the amphiphilic hyperbranched polymers could form relatively homogeneous and densely packed shell around the gold core revealed by transmission electron microscopy. Stability experiments showed that the solution of AuNPs coated with the amphiphilic hyperbranched polymers were more stable than those coated with their linear analogs. Moreover, the AuNPs capped with the amphiphilic hyperbranched polymers could be also stored in dryness for long time.Amphiphilic hyperbranched polymers showed better ability to extract and stabilize the citrate-protected large gold nanoparticles into chloroform than their corresponding linear analogs.
Co-reporter:Xing-Long Lou;Fa Cheng ;Peng-Fei Cao;Qiang Tang;Hua-Ji Liu Dr. Dr.
Chemistry - A European Journal 2009 Volume 15( Issue 43) pp:11566-11572
Publication Date(Web):
DOI:10.1002/chem.200901244
Abstract
Hyperbranched polyethylenimine (HPEI) was simply mixed with a solution of amphiphilic calix[4]arene (AC4), which possesses four phenol groups and four aliphatic chains, in chloroform. This resulted in the novel supramolecular complex HPEI–AC4 through the noncovalent interaction of the amino groups of HPEI with the phenol groups of AC4. The formed HPEI–AC4 supramolecular complexes were characterized by 1H NMR spectroscopy and dynamic light scattering. The cationic water-soluble dye methyl blue (MB) and the anionic water-soluble dye methyl orange (MO) were used as the model guests to test the performance of HPEI–AC4 as a supramolecular nanocarrier. It was found that HPEI–AC4 could accommodate the anionic water-soluble MO guests into the HPEI core. The MO encapsulation capacity of HPEI–AC4 was pH sensitive, which reached maximum loading under weakly acidic conditions. The loaded MO molecules could be totally released when the pH value was reduced to be around 4.5 or raised to be around 9.5, and this process was reversible. HPEI–AC4 could not only accommodate the anionic MO with the HPEI core but could also simultaneously load the cationic MB molecules using the formed AC4 shell, thereby realizing the site isolation of the two kinds of functional units. The amount of MO and MB encapsulated by HPEI–AC4 could be controlled by varying the ratio of hydroxyl groups of AC4 to amino groups of HPEI.
Co-reporter:Peng-Fei Cao;Rui Xiang;Xun-Yong Liu;Chun-Xiao Zhang;Fa Cheng
Journal of Polymer Science Part A: Polymer Chemistry 2009 Volume 47( Issue 19) pp:5184-5193
Publication Date(Web):
DOI:10.1002/pola.23568
Co-reporter:Xunyong Liu, Fa Cheng, Huaji Liu and Yu Chen
Soft Matter 2008 vol. 4(Issue 10) pp:1991-1994
Publication Date(Web):01 Aug 2008
DOI:10.1039/B811012N
Compared with linear thermoresponsive polymers hyperbranched ones having spheroid-like structure exhibited an unusual salt effect: a non-linear LCST decrease upon increasing the concentration of various salts such as NaCl, KCl or Na2SO4 has been observed. The LCST variation of such polymers was more sensitive to the presence of salt.
Co-reporter:Xulong Cao, Zhenquan Li, Xinwang Song, Xiaohong Cui, Pengfei Cao, Huaji Liu, Fa Cheng, Yu Chen
European Polymer Journal 2008 Volume 44(Issue 4) pp:1060-1070
Publication Date(Web):April 2008
DOI:10.1016/j.eurpolymj.2008.01.035
Core-shell type multiarm star copolymers with poly(ε-caprolactone) (PCL) as shells and hyperbranched polyethylenimine (PEI) as core have been successfully prepared by the Sn(Oct)2 catalyzed ring-opening polymerization of ε-caprolactone (CL) using high molecular weigh PEIs directly as macroinitiators. The initiation efficiency is in the range of 91–95% for PEI with Mn = 104 (PEI10K) and only around 60% for PEI with Mn = 2.5 × 104 (PEI25K), leading to star polymers with an average arm number in the range of 155–276. The thermal property of the obtained multiarm star polymers were also investigated by DSC. The melting and crystallization temperatures of the star polymers increase as the PCL arm length increases when the PEI core is fixed. The fusion enthalpy, crystalline enthalpy and degree of crystallinity values of the star polymers with PEI10K core are less than those with PEI1.8K core. Due to the polarity difference between PCL arm and PEI core, the resulting multiarm star polymers can act as inverted micellar nanocapsules capable of extracting and encapsulating water soluble guests. Increasing the size and polarity of the hydrophilic PEI core of the star nanocapsules are two effective ways to enhance their hydrophilic guest encapsulation capacity. Increasing the hydrophobic PCL arm length can increase the molar ratio, whereas reduce the weight ratio of the encapsulated hydrophilic guests to the star nanocapsules. Unexpectedly, the obtained nanocapsules can entrap the bigger size hydrophilic congo red guests more than the smaller size methyl orange.
Co-reporter:Yu Chen, Johan Loccufier, Luc Vanmaele and Holger Frey
Journal of Materials Chemistry A 2007 vol. 17(Issue 32) pp:3389-3392
Publication Date(Web):17 Jul 2007
DOI:10.1039/B708986D
A new class of hyperbranched polymeric photoinitiators with built-in amine coinitiators has been developed, showing high functionality, low viscosity, good compatibility with the usual radiation curable formulations, high photoactivity and low extractability from the cured sample.
Co-reporter:Huaji Liu;Zhong Shen
Journal of Polymer Science Part A: Polymer Chemistry 2007 Volume 45(Issue 6) pp:1177-1184
Publication Date(Web):6 FEB 2007
DOI:10.1002/pola.21878
Thermoresponsive hyperbranched polymers were prepared and their lower critical solution temperatures in aqueous media were sensitive to the change of molecular weight, degree of substitution of IBAm groups, and acidity of the solution.
Co-reporter:Huaji Liu, Yu Chen, Dandan Zhu, Zhong Shen, Salah-Eddine Stiriba
Reactive and Functional Polymers (May 2007) Volume 67(Issue 5) pp:383-395
Publication Date(Web):May 2007
DOI:10.1016/j.reactfunctpolym.2007.01.009
Co-reporter:Huaji Liu, Yu Chen, Zhong Shen, Holger Frey
Reactive and Functional Polymers (February 2007) Volume 67(Issue 2) pp:156-164
Publication Date(Web):February 2007
DOI:10.1016/j.reactfunctpolym.2006.10.011
Co-reporter:Man-Ling Wang, Ting-Ting Jiang, Yang Lu, Hua-Ji Liu and Yu Chen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 19) pp:NaN5933-5933
Publication Date(Web):2013/03/12
DOI:10.1039/C3TA10293A
Hyperbranched polyethylenimine (HPEI) modified polyacrylonitrile fiber (PANF) was prepared through a water mediated hydrolysis and amidation reaction in an autoclave. The grafting amount of HPEI onto PANF could be modulated conveniently by varying the preparation conditions, such as reaction temperature, reaction time and the feed ratio of HPEI to PANF. The Young's modulus of the PANF decreased with the grafting of HPEI, especially when more HPEIs were grafted. As for the PANF-g-HPEI with low HPEI content, the Young's moduli were similar before and after loading of AuNPs, whereas the loading of AuNPs obviously deteriorated the strength of the fibers with high HPEI content. From the nitrogen adsorption and desorption isotherms, it could be seen that PANF contained nanometer sized pores, and the grafting with HPEI did not affect the pore size, but did reduce the surface area. Moreover, the loading of AuNPs into PANF-g-HPEI also did not influence the pore size, but decreased the surface area. FTIR and XPS analyses demonstrated that the obtained PANF-g-HPEI not only contained a large amount of amino groups from the HPEI moiety, but also many carboxylate ions due to the hydrolysis of the cyano groups of PANF. XRD characterization proved that the inner crystal region of PANF was partially broken by the introduction of HPEI moieties. SEM showed that the PANFs swelled up after grafting with HPEI, and the increase of the grafting efficiency led to a larger average diameter of the fibers. When the grafting amount of HPEI onto PANF reached as high as 97%, the surface of the fibers was severely impaired. The obtained PANF-g-HPEIs could be successfully used as supporters and stabilizers in the preparation of small-sized AuNPs. TEM characterization showed that the mixing time of PANF-g-HPEIs with HAuCl4 aqueous solution affected the size and size distribution of the formed AuNPs, and the optimal mixing time was around 0.5 h. The average diameter of the obtained AuNPs was around 3.0 nm at a feed ratio of amino groups of PANF-g-HPEI to Au atoms ([N]:[Au]) of 200, independent of HPEI content of the PANF-g-HPEIs used. Reducing the [N]:[Au] feed ratio increased the average size of the obtained AuNPs. The AuNPs supported by PANF-g-HPEIs could be used as efficient catalysts for the heterogeneous catalytic reduction of 4-nitrophenol by NaBH4. The PANF-g-HPEI with lower HPEI content endowed the supported AuNPs with a slightly higher catalytic rate. These heterogeneous AuNP catalysts could be conveniently recovered and reused many times, especially the AuNPs supported by the PANF-g-HPEIs containing a low content of HPEI. The turnover number (TON) values of the AuNPs supported by PANF-g-HPEI0.31 and PANF-g-HPEI0.58 could reach more than 5 × 104, which is unprecedented in the catalytic reduction of 4-nitrophenol.
Co-reporter:Yi Liu, You Fan, Yuan Yuan, Yu Chen, Fa Cheng and Shi-Chun Jiang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 39) pp:NaN21182-21182
Publication Date(Web):2012/08/22
DOI:10.1039/C2JM34445A
A series of organo-soluble gold nanoparticles (AuNPs) were prepared through the reduction of HAuCl4 by NaBH4 in the presence of amphiphilic hyperbranched copolymers bearing a hydrophilic hyperbranched polyethylenimine (PEI) core and a hydrophobic dendritic shell. For comparison, the corresponding analogues with a PEI core and a linear shell were also used to prepare the organo-soluble AuNPs. All the obtained AuNPs were characterized by transmission electron microscopy. It was found that under a high feed ratio of polymer to HAuCl4, the average diameter of the obtained small AuNPs was similar, and was independent of the shell morphology of the hyperbranched polymeric stabilizers. Reducing the feed ratio of polymer to HAuCl4 led to the formation of larger AuNPs and irregularly shaped AuNP aggregates. The stability evaluation on the basis of two-month shelf-storage demonstrated that the obtained AuNPs were stable under shelf-storage regardless of whether the shell of the hyperbranched polymeric stabilizer was dendritic or linear. These organo-soluble AuNPs could be used as efficient catalysts for the biphasic catalytic reduction of 4-nitrophenol by NaBH4, and could also be conveniently recovered and reused. The stabilizers with a dendritic shell endowed the AuNP catalyst with a higher performance than the corresponding stabilizers with a linear shell, including: (1) a higher catalytic rate; (2) the ability to be recovered and reused more times; (3) a maximal turnover number of around 23000, which is unprecedented in the catalytic reduction of 4-nitrophenol.
Co-reporter:Xun-Yong Liu, Fa Cheng, Yi Liu, Wen-Gang Li, Yu Chen, Hong Pan and Hua-Ji Liu
Journal of Materials Chemistry A 2010 - vol. 20(Issue 2) pp:NaN284-284
Publication Date(Web):2009/11/03
DOI:10.1039/B916125B
Thermoresponsive gold nanoparticles (AuNPs) with lower critical solution temperature (LCST) adjustable over a broad range were explored to be potentially used as colorimetric sensors. Upon raising the temperature above the LCST the surface plasmon resonance (SPR) peaks of the obtained thermoresponsive AuNPs red-shifted sharply in a narrow temperature range, accompanied by a color transition from transparent red to transparent purple–red until turbid red, which made them suitable to be used as sensitive colorimetric sensors for detecting environmental temperature variation. Moreover, the temperature range of sensitivity of the obtained thermoresponsive AuNPs could be tuned by modulating the molecular weight of core or degree of substitution of the thermoresponsive polymers employed. Furthermore, the solution colors of the thermoresponsive AuNPs were also sensitive to pH and NaCl concentration variation, as a result of which they could also be used as colorimetric sensors for detecting the variation of pH and salt concentration.
Co-reporter:Xun-Yong Liu, Fa Cheng, Yi Liu, Hua-Ji Liu and Yu Chen
Journal of Materials Chemistry A 2010 - vol. 20(Issue 2) pp:NaN368-368
Publication Date(Web):2009/11/06
DOI:10.1039/B915313F
Novel thermoresponsive gold nanoparticles (AuNPs) with lower critical solution temperature (LCST) were obtained through the non-covalent interaction between a thermoresponsive hyperbranched polyethylenimine with isobutyramide groups (HPEI-IBAm) and citrate-protected AuNPs. The LCSTs of the thermoresponsive AuNPs could be conveniently modulated over a broad range by altering the molecular weight of the HPEI core, the degree of substitution (DS) of the IBAm groups of the HPEI-IBAm polymers or the pH of the solution. The obtained thermoresponsive AuNPs could be used as recyclable responsive catalysts for the reduction reaction of 4-nitrophenol by NaBH4. As far as the thermoresponsive catalysts were concerned, reducing the molecular weight of the HPEI core, lowering the DS values and increasing the concentrations of the capping HPEI-IBAm polymers or the gold resulted in the acceleration of the reaction. By choosing the right capping HPEI-IBAm polymers, the reaction was faster than that catalyzed by AuNPs without capping polymers. The reaction rate was accelerated by elevating the reaction temperature at first, but reached a plateau or decelerated upon raising the temperature close to the LCSTs of the thermoresponsive AuNPs catalysts. Moreover, the obtained thermoresponsive AuNP catalysts could be recovered by heating the temperature above their LCSTs and be recycled at least six times with more than 95% conversion.
Co-reporter:Yu Chen, Johan Loccufier, Luc Vanmaele and Holger Frey
Journal of Materials Chemistry A 2007 - vol. 17(Issue 32) pp:NaN3392-3392
Publication Date(Web):2007/07/17
DOI:10.1039/B708986D
A new class of hyperbranched polymeric photoinitiators with built-in amine coinitiators has been developed, showing high functionality, low viscosity, good compatibility with the usual radiation curable formulations, high photoactivity and low extractability from the cured sample.
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