JOURNAL OF POLYMER SCIENCE
·
2022
·Vol. 60
·期 24
·3463-3470
·
IF 3.046
Dong Xing,Jiajia Li,Miao Chen,Na Li,Xiangqiang Pan,Zhengbiao Zhang,Jian Zhu
Light-regulated polymerization has emerged as a powerful tool to control the process of polymerization. However, tuning the polymer molecular weight distribution (MWD) by light is still not well developed. Here, we present a convenient approach for controlling the MWD in reversible addition-fragmentation chain transfer (RAFT) polymerization by exploiting an ultraviolet light-induced RAFT-hetero-Diels – Alder (RAFT-HDA) reaction with a photoenol diene. The key point in this strategy is to terminate part of the propagating chains at a specific time by the RAFT-HDA reaction. In addition, a photoenol diene with a hydroxyl group is also synthesized and successfully applied to realize this strategy, which can be further utilized for chain extension of ɛ -caprolactone ( ɛ -CL) by ring opening polymerization to prepare diblock copolymers with different MWDs. Graphical
研究领域:
材料科学
·
化学工程
·
高分子化学
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DOI
高影响因子
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
·
2018
·Vol. 56
·期 21
·2437-2444
·
IF 2.588
Lei Yu,Yanlong Wei,Yuanyuan Tu,Shudong Lin,Zhenzhu Huang,Jiwen Hu,Yue Chen,Hang Qiao,Wei Zou
We report herein a visible light-induced metal-free living polymerization with high oxygen tolerance that can be performed in aqueous media. In contrast with ordinary living/controlled radical polymerizations, oxygen can be present throughout the entire reaction process. This reaction can be photo-induced and proceeds at room temperature. First, we have successfully synthesized a well-defined polymer in an ambient atmosphere by the photo-induced radical polymerization method, using acrylic acid as a monomer and fluorescein as a photocatalyst. However, the subsequent chain extension reaction did not occur, possibly due to oxidation of the chain transfer agent (CTA). Despite this, we found that the addition of vitamin C (ascorbic acid) imparted the process with oxygen tolerance. We conducted a systematic study to optimize the best concentrations of the key reagents including the monomer, CTA, fluorescein, and vitamin C. Through these optimizations we were able to synthesize in the presence of oxygen a series of well-defined poly(acrylic acid)s (PAAs) with dispersities ( Ð ) below 1.3 and molecular weights that closely matched the theoretical values. The kinetic study showed that the molecular weight of the produced PAA increased linearly with the conversion of the monomer, and chain extension reaction also yielded a block polymer with a higher molecular weight than that of the previous polymer. Therefore, we developed a novel photo-induced living polymerization method that can be conducted both in the absence of oxygen and in the presence of air. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56 , 2437–2444
研究领域:
高分子化学
·
材料科学
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DOI
高影响因子
POLYMERS FOR ADVANCED TECHNOLOGIES
·
2019
·Vol. 31
·期 3
·407-414
·
IF 2.162
Hongxin Wang,Baijun Liu,Mingyao Zhang,Shuai Du,Gaocheng Wu,Yiwei Hu,Jinhui Zhang,Xiangchi Liu
The increasing demand for monodispersed cross-linked polymers in high-quality applications requires continuous improvement in their preparation process. In this study, an appropriate amount of a chain transfer agent was added to a traditional cross-linking system, resulting in the preparation by one-step dispersion polymerization of cross-linked polystyrene (PS) microspheres with a particle size of 3.867 μm and a diameter coefficient of variation of 0.011. The particles were characterized using scanning electron microscopy (SEM) and an Ubbelohde viscometer. The results show that the tertiary dodecyl mercaptan (TDDM) chain transfer during nucleation increases the oligomer concentration, promotes the aggregation of the oligomers, increases the primary particle size, and reduces the cross-linking effect. This controls the volume of cross-linked chains in the primary particles, thus avoiding the problem of poor dispersion of the polymer microspheres due to the introduction of divinylbenzene (DVB). This study produces a preparation method for cross-linked microspheres.
研究领域:
材料科学
·
高分子化学
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DOI
高影响因子
Pigment & Resin Technology
·
2021
·Vol. 51
·期 5
·499-507
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IF 1.263
Hongyi Tu,Donglei Liu,Zhenbin Chen,Chunli Liu
PurposeUsing a reversible addition fragmentation chain transfer reaction, a series of resins were prepared by using N, N-diethyl acrylamide (DEA), poly (ß-hydroxyethyl methacrylate) (PHEMA) as hydrophilic blocks and poly (glycidyl methacrylate) (PGMA) as hydrophobic blocks (and as a target for immobilizing penicillin G acylase [PGA]) and the low critical solution temperature (LCST) of which could be adjusted by changing the segment length of blocks.Design/methodology/approachTo make the catalytic conversion temperature of immobilized PGA fallen into the temperature range of the sol state of thermosensitive block resin, a type of thermosensitive block resin, i.e. PDEA-b-PHEMA-b-PGMA (DHGs) was synthesized to immobilize PGA, and the effect of segment order of block resin was investigated on the performance of PGA.FindingsCarrier prepared with monomers molar ratio of n(DEA) : n(HEMA): n(GMA) = 100: 49: 36 presented loading capacity (L) and enzyme activity recovery ratio (Ar) of 110 mg/g and 90%, respectively, and a block resin with LCST value of 33 °C was essential for keeping higher Ar of PGA.Originality/valuePGA has become an important biocatalyst in modern chemistry industry. However, disadvantages include difficulty in separation, poor repeatability and high cost, which limits the scope of PGA applications. The effective method is to immobilize the enzyme to the carrier, which could overcome the disadvantage of free enzyme.
研究领域:
生物化学
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材料科学
·
酶工程
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DOI
高影响因子
Polymer Chemistry
·
2021
·Vol. 12
·期 18
·2743-2751
·
IF 5.582
Wei Wen,Aihua Chen
Polymerization induced hierarchical self-assembly (PIHSA) has been developed as a facile and robust method to prepare non-spherical polymer nanoparticles at high solid content. But the current PIHSA formulations are limited to linear liquid crystalline (LC) block copolymers (BCPs). Besides, the non-spherical morphology library is desired to be enriched for more morphology-dependent applications. In this work, intramolecularly folded single chain nanoparticles (SCNPs) with steric character are used as stabilizers to construct reversible addition–fragmentation chain transfer (RAFT) dispersion PIHSA formulation for the first time. The study of the polymerization kinetics illustrates the controlled characteristic. The influence of SCNP stabilizers on the self-assembly behavior is investigated in detail by tuning the polymerization degree of core-forming blocks, solid contents, and intrachain cross-linking degree of the SCNPs. The results suggest that the morphology evolution is significantly affected by the architecture of the SCNP stabilizers. Under the synergistic effect of the steric architecture of the outside SCNP stabilizers and internal LC ordering, a unique morphology evolution of sphere–cuboid–holbrick–jujube, rather than typical sphere to one-dimensional morphology, was observed. This work provides a facile route to polymeric nanoparticles with unique non-spherical morphologies and demonstrates that introducing SCNP into polymerization induced self-assembly formulation is a promising approach for morphological control.
研究领域:
高分子化学
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纳米材料科学
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自组装
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功能高分子
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胶体与界面化学
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DOI
高影响因子
POLYMER
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2015
·
IF 3.562
Xue Jiang,Chun Feng,Guolin Lu,Xiaoyu Huang
A homopolymer strategy was developed to synthesize temperature and pH/CO 2 stimulus-responsive homopolymers. A new class of acrylamide monomers bearing oligo(ethylene glycol) unit and N,N -diethylaminoethyl group were designed and prepared through Aza-Michael addition reaction followed by amidation with acryloyl chloride using amino group as a linkage to connect oligo(ethylene glycol), N,N -diethylaminoethyl, and polymerizable double bond groups together. Subsequently, the corresponding homopolymers containing oligo(ethylene glycol) unit and N,N -diethylaminoethyl group in each repeated unit were prepared via RAFT polymerization with controlled molecular weights and relatively narrow molecular weight distributions . The lower critical solution temperature (LCST) of homopolymer was examined to be influenced by molecular weight, salt concentration, and pH value of aqueous solution. The LCSTs of homopolymers could be tuned in a wide temperature window by changing pH value of aqueous solution and it increased with the decrease of pH value. Particularly, CO 2 gas as a unique pH stimulus can also reversibly adjust the solubility of homopolymer without the addition of acids or bases.
研究领域:
高分子化学
·
智能材料
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药物递送
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生物医用材料
·
刺激响应材料
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DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2024
·
IF 3.8
Yuhang He,Hua Ke,Yangcheng Lu
The copolymerization of ethylene vinyl acetate (VAc) at 4.0 MPa and 75 °C has been studied experimentally and computationally in four organic solvents, namely, methanol (MeOH), tert-butyl alcohol (TBA), methyl acetate (MA), and dimethyl carbonate (DMC), to reveal the effect of the solvents on copolymerization. The results show a significant dependence of the copolymerization rate and reactivity ratio on the nature of the solvent. Polymerization rate constants decrease in the order of TBA > MeOH > DMC > MA. The results from FTIR spectra and complexation energy calculation suggest that the variance of the copolymerization rate is closely related to the interaction between the monomer and the solvent. A stronger interaction between the monomer and the solvent might decrease the average effective monomer concentration. Various reactivity ratios are interpreted in terms of the stabilization effect of the solvent on electron-deficient species that changes the selectivity of macroradicals. Density functional theory (DFT) calculation performs well in predicting the change in the reactivity ratio in different solvents. The molecular weight of the ethylene vinyl acetate copolymer is remarkably affected by the solvents due to the chain transfer reaction, while the unit sequence is little affected.
研究领域:
高分子科学
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化学工程
·
材料科学
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DOI
高影响因子
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
·
2013
·Vol. 52
·期 1
·87-95
·
IF 3.543
Aihua Li,Jingquan Liu,Guozhen Liu,Jizhen Zhang,Shengyu Feng
In this article, the preparation of fluorescent nanohybrids with core–shell structure and metal-enhanced fluorescence (MEF) effect was presented. The fluorescent core–shell nanohybrids were prepared using silver nanoparticles (AgNPs) as cores and fluorophore tethered thermoresponsive copolymers with tunable lower critical solution temperature (LCST) from 15 to 90 °C as shells. These thermoresponsive copolymers were synthesized by the random copolymerization of oligo(ethylene oxide) acrylate and di(ethylene oxide) ethyl ether acrylate using reversible addition–fragmentation chain transfer polymerization and grafted on to AgNPs surface via Ag–S coordination interaction. By thermal manipulation of polymer spacer between AgNPs and fluorophores, the tunable MEF was achieved. It was also revealed that the fluorescent nanohybrids would exhibit maximal MEF when the polymerization degree was tuned to 350. The manipulation of the solution temperatures below and above LCST resulted in switchable MEF behavior. In addition, the phase transition process of the thermoresponsive copolymer was also studied by MEF effect using this fluorescent core–shell nanohybrid design. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52 , 87–95
研究领域:
材料科学
·
纳米技术
·
高分子化学
·
物理化学
·
光学
·
表面科学
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DOI
高影响因子
MACROMOLECULES
·
2018
·
IF 5.914
Congguang Zheng,Yan Zhou,Yanpeng Jiao,Huiqi Zhang
Controlled preparation of narrow or monodisperse, physically cross-linked, and “living” spherical polymer particles by one-stage reversible addition–fragmentation chain transfer (RAFT) precipitation polymerization (RAFTPP) is described for the first time. The introduction of RAFT polymerization mechanism into precipitation polymerization system, together with the use of methacrylic acid (MAA) (capable of forming hydrogen bonding) as the monomer, allows ready generation of uniform spherical poly(MAA) (PMAA) particles with surface-bound “living” dithioester groups, easily tunable sizes, and low molecular weights in the absence of any cross-linking monomer. The polymerization parameters (i.e., monomer loading, molar ratio of the RAFT agent to free radical initiator, and polymerization temperature) showed much influence on the morphologies and yields of PMAA particles, and their simple adjustment allows fine-tuning of “living” PMAA particle sizes. The presence of dithioester groups on such PMAA particles was confirmed not only by their light pink color and characteristic UV–vis absorbance peak of dithioester units but also by their capability of directly grafting cross-linked apolar polymer shells. Some uniform “living” PMAA-based functional copolymer microspheres were also prepared in a one-stage process by simply incorporating glycidyl methacrylate, 2-hydroxyethyl methacrylate, or a fluorescent monomer into the RAFTPP of MAA, demonstrating the high versatility and general applicability of the RAFTPP system. The polymerization of MAA in RAFTPP proved to occur both in the continuous phase and on PMAA particle surfaces instead of inside particles, and a combined “grafting from” and “grafting to” particle growth mechanism is proposed for RAFTPP.
研究领域:
高分子化学
·
材料科学
·
大分子化学
·
胶体与界面科学
·
化学合成
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DOI
高影响因子
危险品化学品经营许可证（带存储）