Synthesis of polystyrene-styrene/butadiene diblock copolymers via reversible addition-fragmentation chain transfer miniemulsion polymerization

Polystyrene-styrene/butadiene diblock copolymers were synthesized via reversible addition-fragmentation chain transfer （RAFT） miniemulsion polymerization.During the polymerization process,the molecular weight distribution was narrow and the numerical molecular weight of the copolymers increased with increasing conversion of monomers,which was close to the theoretical.FT-IR and ^1H NMR results indicated that the microstructure of the polymer was mainly 1,4-trans-butadiene with small amount of 1,2-units,and composition in the copolymers was obtained.

Grafting of MIPs from PVDF Membranes via Reversible Addition-fragmentation Chain Transfer Polymerization for Selective Removal of p-Hydroxybenzoic Acid

Effective molecularly imprinted membranes（MIMs） were developed as an efficient adsorbent for the selective removal ofp-hydroxybenzoic acid（p-HB） from acetylsalicylic acid（ASA, aspirin）. The MIMs were grafted successfully from poly（vinylidene fluoride） microfiltration membranes via reversible addition-fragmentation chain transfer（RAFT） polymerization. The graft copolymerization of acrylic acid（AA） in the presence of template p-hydroxybenzoic acid led to molecularly imprinted polymer（MIP） film coated membranes. The obtained MIMs were characterized by scanning electron microscopy（SEM）, Fourier transform infrared spectrophotometer（FTIR） and Raman spectra, and batch mode adsorption studies were carried ont to investigate the specific adsorption equilibrium, kinetics and selective recognition properties of different MIMs. The kinetic properties of the MIMs could be well described by the pseudo-second-order rate equation. Selective permeation experiments were performed to evaluate the permeation selectivity of the p-HB imprinted membranes. The observed performances of the MIMs are applicable to the further purification of aspirin. Keywords Acetylsalicylic acid; Reversible addition-fragmentation chain transfer; Molecularly imprinted membrane; p-Hydroxybenzoic acid; Selective adsorption

几种不可逆加成-断裂型链转移剂在苯乙烯乳液聚合中的研究

研究了基于不可逆加成-断裂链转移机理的3种分子质量调节剂对苯乙烯乳液聚合的影响。主要考察了3种链转移剂对乳液聚合速率、乳胶粒子大小以及聚苯乙烯数均相对分子质量的影响。链转移剂的内在动力学、扩散和自由基解吸附行为决定了其分子质量调节效率、对聚合速率的影响程度和乳胶粒子大小。链转移常数高的α-苯磺酰甲基丙烯酸乙酯使苯乙烯乳液聚合速率下降明显,乳胶粒子粒径分布较宽,且聚合后期不能有效调节聚苯乙烯分子质量;而链转移常数相对较小的2,3-二氯丙烯对聚合速率和乳胶粒子粒径的影响轻微,并能全程控制聚苯乙烯分子质量;分子质量较大的正十二烷基-2-苯基烯丙基硫则因在乳液体系中的扩散较慢,难以调节聚苯乙烯的分子质量。

不可逆加成-断裂链转移剂正丁基-2-苯基烯丙基硫在苯乙烯乳液聚合中的研究

基于不可逆加成-断裂链转移机理,研究了正丁基-2-苯基烯丙基硫(BPAS)作为分子量调节剂对苯乙烯乳液聚合速率、乳胶粒子大小和聚合物数均分子量的影响。结果表明,BPAS存在下的苯乙烯乳液聚合速率有所下降,乳胶粒子粒径减小,这是由于乳胶粒子中自由基的解吸附;平均一个乳胶粒子中的自由基个数依赖于BPAS浓度;BPAS在苯乙烯乳液聚合整个过程中能有效调节聚合物分子量,其调节效率与温度无关,同时能与经典的数均分子量数学模型相匹配。

几种烯丙基硫类不可逆加成断裂链转移剂在苯乙烯乳液聚合中的应用

合成了4种烯丙基硫类不可逆加成断裂链转移剂,研究了4种链转移剂在苯乙烯乳液聚合中的应用,考察了4种链转移剂对乳液聚合速率、乳胶粒子大小的影响以及对聚合物相对分子质量的调控规律。正辛基-2-苯基烯丙基硫加入体系后出现浮油现象,难以有效调节聚苯乙烯的相对分子质量;异辛基-2-苯基烯丙基硫对聚合速率影响很小,对相对分子质量有一定的调控效果;正戊基(2)-2-苯基烯丙基硫和叔丁基-2-苯基烯丙基硫对聚苯乙烯相对分子质量的调控效率高于异辛基-2-苯基烯丙基硫,但聚合速率均有一定程度的下降,在整个聚合过程中正戊基(2)-2-苯基烯丙基硫和叔丁基-2-苯基烯丙基硫体系中聚苯乙烯的相对分子质量几乎保持不变,且改变其用量,可有效调节聚合物的相对分子质量。

Molecularly Imprinted Polymers on Chloromethyl Polystyrene Resin Prepared via RAFT Polymerization

Surface molecularly imprinted polymers （SMIP） was prepared via the reversible addition-fragmentation chain transfer （RAFT） polymerization on the chloromethyl polystyrene resin （CPR） in the presence of the template D-phenylalanine. The structure of SMIP was characterized by FTIR and SEM. The adsorption behavior of D-phenylalanine of SMIP was preliminarily investigated.

乳聚ABS树脂分子量调节剂的制备

不可逆加成-断裂链转移剂合成容易,产率高,无恶臭,广泛用于分子量的调节。本文通过α-甲基苯乙烯溴代后与硫醇类链转移剂合成十二烷基二苯基硫烯丙基硫型不可逆加成链转移剂,用于调节ABS分子量,研究了分子量调节剂对丙烯腈-丁二烯-苯乙烯树脂(ABS)分子量及其它性能的影响,通过红外光谱仪、核磁共振氢谱仪对产物的结构进行表征,结果表明已成功地合成出目标产物。

Effect of Phase Separation Size on the Properties of Self-healing Elastomer

Regulation of phase structure has been recognized as one of the most effective ways to fabricate self-healing polymers with high mechanical strength.The mechanical properties of the resultant polymers are certainly affected by the size of separated phase domain.However,the study on this aspect is absence,because it can hardly exclude the influence of variation in monomer proportion required for tuning the separated phase size.Here,we report the first study on tuning the phase size through reversible addition-fragmentation chain transfer(RAFT)polymerization without changing the proportion of monomers.As expected,the size of separated phase has been successfully mediated from 15 nm to 9 nm by tuning the molecular weight of the chain transfer agent.It is found that the mechanical strength and the self-healing efficiency of the resultant polymers increase simultaneously with the decrease of phase size.The study on the formation kinetics of hydrogen bonds reveals that the decrease of phase size can facilitate the re-bonding rate of hydrogen bonds,even if the migration of polymer chains is restricted.

Enzyme-assisted Photoinitiated Polymerization-induced Self-assembly in Continuous Flow Reactors with Oxygen Tolerance

Polymerization-induced self-assembly(PISA)is an emerging method for the preparation of block copolymer nano-objects at high concentrations.However,most PISA formulations have oxygen inhibition problems and inert atmospheres(e.g.argon,nitrogen)are usually required.Moreover,the large-scale preparation of block copolymer nano-objects at room temperature is challenging.Herein,we report an enzyme-assisted photoinitiated polymerization-induced self-assembly(photo-PISA)in continuous flow reactors with oxygen toleranee.The addition of glucose oxidase(GOx)and glucose into the reaction mixture can consume oxygen efficiently and constantly,allow the flow photo-PISA to be performed under open-air conditions.Polymerization kinetics indicated that only a small amount of GOx(0.5 μmol/L)was needed to achieve the oxygen tolerance.Block copolymer nano-objects with different morphologies can be prepared by varying reaction conditions including the degree of polymerization(DP)of core-forming block,monomer concentration,reaction temperature,and solvent composition.We expect this study will provide a facile platform for the large-scale production of block copolymer nano-objects with different morphologies at room temperature.

Mechanism study and molecular design in controlled/“living” radical polymerization

This tutorial review summarizes recent progress in the research field of controlled/"living" radical polymerization (CLRP) from Soochow University.The present paper gives a broad overview of the mechanism study and molecular design in CLRP.The mechanism study in CLRP aided by microwave,initiated by γ-radiation at low temperature,mediated by iron,in reversible addition-fragmentation chain transfer (RAFT) polymerization and the mechanism transfer between different CLRP processes are reviewed and summarized.The molecular design in CLRP,especially in RAFT polymerization for mechanism study,and in achieving tailor-made functional polymers is studied and discussed in the later part.

Preparation of ABA triblock copolymer assemblies through “one-pot” RAFT PISA

Poly(N,N-dimethyl acrylamide)-block-poly(styrene)-block-poly(N,N-dimethyl acrylamide)(PDMAc-bPSt-b-PDMAc)amphiphilic triblock copolymer micro/nano-objects were synthesized through reversible addition-fragmentation chain transfer(RAFT)dispersion polymerization of St mediated with poly(N,Ndimethyl acrylamide)trithiocarbonate(PDMAc-TTC-PDMAc)bi-functional macromolecular RAFT agent.It is found that the morphology of the PDMAc-b-PSt-b-PDMAc copolymer micro/nano-objects like spheres,vesicles and vesicle with hexagonally packed hollow hoops(HHHs)wall can be tuned by changing the solvent composition.In addition,vesicles with two sizes(600 nm,264 nm)and vesicles with HHHs features were also synthesized in high solid content systems(30 wt%and 40 wt%,respectively).Besides,as compared with typical AB diblock copolymers(A is the solvophilic,stabilizer block,and B is the solvophobic block),ABA triblock copolymers tend to form higher order morphologies,such as vesicles,under similar conditions.The finding of this study provides a new and robust approach to prepare block copolymer vesicles and other higher order micelles with special structure via PISA.

Hydrogels with Dynamically Controllable Mechanics and Biochemistry for 3D Cell Culture Platforms

Many cell-matrix interaction studies have proved that dynamic changes in the extracellular matrix(ECM)are crucial to maintain cellular properties and behaviors.Thus,developing materials that can recapitulate the dynamic attributes of the ECM is highly desired for threedimensional(3 D)cell culture platforms.To this end,we sought to develop a hydrogel system that would enable dynamic and reversible turning of its mechanical and biochemical properties,thus facilitating the control of cell culture to imitate the natural ECM.Herein,a hydrogel with dynamic mechanics and a biochemistry based on an addition-fragmentation chain transfer(AFCT)reaction was constructed.Thiol-modified hyaluronic acid(HA)and allyl sulfide-modifiedε-poly-L-lysine(EPL)were synthesized to form hydrogels,which were non-swellable and biocompatible.The reversible modulus of the hydrogel was first achieved through the AFCT reaction;the modulus can also be regulated stepwise by changing the dose of UVA irradiation.Dynamic patterning of fluorescent markers in the hydrogel was also realized.Therefore,this dynamically controllable hydrogel has great potential as a 3 D cell culture platform for tissue engineering applications.

RAFT Copolymerization of Glycidyl Methacrylate and N,N-Dimethylaminoethyl Methacrylate

In this work, copolymerization of two functional monomers, glycidyl methacrylate （GMA） and N,N-dimethylaminoethyl methacrylate （DMAEMA）, was firstly carried out via reversible addition-fragmentation chain transfer （RAFT） polymerization successfully. The copolymerization kinetics was investigated under the molar ratio of n[GMA＋DMAEMA]o/n[AIBN]o/n[CPDN]o=300/1/3 at 60℃. The copolymerization showed typical ＂living＂ features such as first-order polymerization kinetics, linear increase of molecular weight with monomer conversion and narrow molecular weight distribution. The reactivity ratios of GMA and DMAEMA were calculated by the extended Kelen-Tudos linearization methods. The epoxy group of the copolymer PGMA-co-PDMAEMA remained intact under the conditions of RAFT copolymerization and could easily be post-modified by ethylenedia- mine. Moreover, the modified copolymer could be used as a gene carrier.