Synthesis of poly(vinyl acetate) block copolymers by successive RAFT and ATRP with a bromoxanthate iniferter

Poly(vinyl acetate)-b-polystyrene, poly(vinyl acetate)-b-poly(methyl acrylate) and poly(vinyl acetate)-b-poly(methyl methacrylate) block copolymers with low polydispersity (M(w)/M(n) < 1.25) were prepared by successive reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) employing a bromoxanthate iniferter (initiator-transfer agent-terminator).     

A tracer study of the hydrolysis of methyl methacrylate and methyl acrylate units in homopolymers and copolymers

Homopolymers and copolymers were prepared from methyl methacrylate, methyl acrylate, and styrene by radical reactions at 60°C. Monomers suitably labeled with carbon-14 were used so that it was possible to monitor the hydrolysis of ester groups in the polymers during treatment under alkaline conditions. It was found that methyl acrylate units were hydrolyzed completely whatever their environment in a polymer chain. Under the same conditions only about 9% of the ester groups in a homopolymer of methyl methacrylate reacted; the proportion was increased by the introduction of comonomer units into the polymer chain. For copolymers of methyl methacrylate with methyl acrylate the extent of reaction may be correlated with the lengths of the sequences of methyl methacrylate units.     

Synthesis of poly(methyl methacrylate-co-styrene)-block-polysulfide-block-poly(methyl methacrylate-co-styrene) copolymers by free radical polymerization combined with oxidative coupling

Poly(methyl methacrylate-co-styrene)-block-polysulfide-block-poly(methyl methacrylate-co-styrene) triblock copolymers were synthesized for the first time by the free radical copolymerization of methyl methacrylate (MMA) and styrene (St) in the presence of a thiocol oligomer as a chain transfer agent, followed by chemical oxidation of the remaining SH-end groups. The apparent chain transfer constant of the thiocol SH groups in the copolymerization reaction was estimated from the rate of consumption of the thiol groups versus the overall rate of consumption of the monomers (C_T = 1.28). Based on this value, the chain transfer constant of the thiocol SH groups in St polymerization was calculated . The triblock copolymers synthesized were characterized by SEC and ¹H NMR measurements.     

4-PEG接枝苯乙烯-马来酸酐交替共聚物的合成及功能化

采用普通自由基聚合和可逆加成一断裂链转移（RAFT）自由基聚合方法合成了对位PEG取代苯乙烯（PEG-g-St）和马来酸酐的交替共聚物（P（（PEG—g—St）-alt-MA））,”CNMR分析表明PEG-g-St和马来酸酐单元采取交替的序列结构．利用反应性基团-马来酸酐单元的水解以及胺解可以制备功能性的PEG聚合物．以月桂胺为模型小分子研究了该聚合物的胺解,得到4-PEG-苯乙烯与羧酸基团以及疏水烷烃的交替序列聚合物,该双亲聚合物在水溶液中形成组装体．     

Free‐radical copolymerization of ethyl α‐hydroxymethylacrylate with methyl methacrylate by reversible addition–fragmentation chain transfer

The controlled free‐radical homopolymerization of ethyl α‐hydroxymethylacrylate and copolymerization with methyl methacrylate were performed in chlorobenzene at 70 °C by the reversible addition–fragmentation chain transfer polymerization technique with 2,2′‐azobisisobutyronitrile as the initiator. 2‐Phenylprop‐2‐yl dithiobenzoate and 2‐cyanoprop‐2‐yl dithiobenzoate were used as chain‐transfer agents in the homopolymerization, whereas only the former was used in the copolymerization. All reactions presented pseudolinear kinetics. The effect of the monomer feed ratio on the copolymerization kinetics was examined. The conversion level decreased when the proportion of ethyl α‐hydroxymethylacrylate in the monomer feed was larger. Kinetic studies indicated that the radical polymerizations proceeded with apparent living character according to experiments, demonstrating an increase in the molar mass with the monomer conversion and a relatively narrow molar mass distribution. All copolymers were statistical in chain structure, as confirmed by determinations of the monomer reactivity ratios. The monomer reactivity ratios were determined, and the Mayo–Lewis terminal model provided excellent predictions for the variations of the intermolecular structure over the entire conversion range. Additionally, the chemical modification of poly(ethyl α‐hydroxymethylacrylate) was carried out to introduce glucose pendant groups into the structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5618–5629, 2006     

Living/controlled copolymerization of acrylates with nonactivated alkenes

The living/controlled copolymerization of methyl acrylate with 1‐alkenes and norbornene derivatives through several radical polymerization techniques has been achieved. These techniques include atom transfer radical polymerization, reversible addition–fragmentation transfer polymerization, nitroxide‐mediated polymerization, and degenerative transfer polymerization. These systems display many of the characteristics of a living polymerization process: the molecular weight increases linearly with the overall conversion, but the polydispersity remains low. Novel block copolymers have been synthesized through the sequential addition of monomers or chain extension. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6175–6192, 2004     

异丁基乙烯基醚与受电子单体的可控自由基共聚合

近年来发展起来的“活性” 可控自由基聚合越来越为人们所关注 ,其原因在于采用这种方法不仅可以设计聚合物的分子量 ,得到窄分布聚合物 ,而且聚合条件不象活性离子型聚合那样严格 ,单体适用范围相对较广 .关于烯类单体的活性自由基聚合迄今主要有 :氮氧自由基调控的稳定自由基聚合 (Ｓｔａｂｌｅｆｒｅｅｒａｄｉｃａｌｐｏｌｙｍｅｒｉｚａｔｉｏｎ ,简称ＳＦＲＰ) [1] 、原子转移自由基聚合 (Ａｔｏｍｔｒａｎｓｆｅｒｒａｄｉｃａｌｐｏｌｙｍｅｒｉｚａｔｉｏｎ ,简称ＡＴＲＰ) [2 ] 以及以后发展起来的自由基可逆加成 断链链转移聚合…     

Graft copolymers having hydrophobic backbone and hydrophilic branches. III. Synthesis of graft copolymers having oligovinylpyrrolidone as hydrophilic branch

Graft copolymers were synthesized by the esterification reaction between acrylic copolymers and carboxyl group terminated vinylpyrrolidone oligomer using phase transfer catalysts. Acrylic copolymers were obtained by the radical copolymerization of β-bromoethyl methacrylate, chloromethylstyrene or glycidyl methacrylate with methyl methacrylate. Hydrophilic oligomers were prepared by the radical oligomerization of vinylpyrrolidone using β-mercaptopropionic acid as chain transfer agent. The degree of esterification increased with decreasing the molecular weight of oligomer and with increasing the number of potential grafting sites on polymer backbones. The water dispersibility of graft copolymers increased with increasing the nitrogen content and was therefore dependent on the branch oligomer content.     

Controlled radical copolymerization of N-vinylpyrrolidone with 1,1,1,3,3,3-hexafluoroisopropyl-α-fluoroacrylate

Narrow disperse copolymers of N-vinylpyrrolidone with 1,1,1,3,3,3-hexafluoroisopropyl-α-fluoroacrylate have been prepared for the first time by reversible addition fragmentation chain transfer pseudo-living radical polymerization in the presence of benzyl dithiobenzoate. The relative activities of the monomers indicating the occurrence of alternating copolymerization have been estimated. The copolymerization of equimolar N-vinylpyrrolidone-1,1,1,3,3,3-hexafluoroisopropyl-α-fluoroacrylate mixtures shows typical features of reversible addition fragmentation chain transfer pseudoliving radical polymerization: deceleration of polymerization compared to the classical radical process, degeneration of the gel effect, successive increase in the number-average molecular mass with conversion, and formation of narrow disperse copolymers.     

Water soluble polymeric nanogels by xanthate-mediated radical crosslinking copolymerisation

Branched water-soluble copolymers were obtained by direct radical crosslinking copolymerisation of acrylic acid or acrylamide and N,N'-methylenebisacrylamide at high solid content in the presence of an O-ethylxanthate as a reversible chain transfer agent.     

Determination of chain transfer constant to dodecanethiol in styrene/methyl methacrylate and butyl acrylate/methyl methacrylate copolymerization and effect of chain length on composition and stereochemical configuration of copolymers

Free radical copolymerization of styrene/methyl methacrylate (S/MMA) and butyl acrylate/methyl methacrylate (BA/MMA) in the presence of n-dodecanthiol (DDT) has been studied at 60°C in a 3 mol/L benzene solution using 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. Overall chain transfer constant to DDT has been determined for both copolymerization systems, as a function of monomer feed composition using complete molecular weight distribution and the Mayo method. Overall transfer coefficients have values which are dependent on both monomer feed composition and individual comonomer transfer values. Composition, sequence distribution, and stereoregularity of copolymers obtained are, in our experimental conditions, independent of copolymer molecular weight. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2913–2925, 1998     

Synthesis and polymerizations of methyl 3,3-difluorocyclobutene-1-carboxylate and methyl 3,3,4,4-tetrafluorocyclobutene-1-carboxylate

Two new monomers, methyl 3,3-difluorocyclobutene-1-carboxylate (MDFC) and methyl 3,3,4,4-tetrafluorocyclobutene-1-carboxylate (MTFC), were synthesized. Under free radical conditions, MDFC gave homopolymer; MTFC did not. Copolymerizations of these monomers showed them to behave as very electron-deficient monomers, MTFC more so than MDFC. MDFC copolymerized with various vinyl ethers and styrenes to give high yields of almost 1:1 copolymers. Acrylonitrile copolymerized in lower yield with less incorporation of MDFC; trimethylethylenetricarboxylate did not copolymerize. Bicyclobutane-1-carbonitrile copolymerized well. MTFC copolymerized with the very electron-rich monomers t-butyl vinyl ether and p-methoxystyrene, leading to alternating and nearly alternating copolymers, respectively, and even styrene tended to give almost 1:1 copolymers. Acrylonitrile gave only polyacrylonitrile, and trimethylethylenetricarboxylate did not react with MTFC under free radical conditions. The reaction of MTFC with the electron-rich monomers t-butyl vinyl ether and p-methoxystyrene occurred spontaneously via charge transfer complexes. Thermally, the copolymers were rather stable, those of MTFC more so than those of MDFC.     

Photothermal degradation of copolymers of methyl methacrylate and n-butyl acrylate

The photothermal degradation of copolymers of methyl methacrylate (MMA) and n-butyl acrylate (n-BuA) covering the whole composition range has been studied at 165°.The gaseous products, which are relatively minor, are hydrogen, carbon monoxide and methane. The liquid products are predominantly MMA, with n-BuA, n-butanol and n-butyraldehyde as minor products. Infra-red spectral changes in the residue were attributed to lactone formation and associated with butanol formation as in the purely thermal reaction The “cold ring” or chain fragment fraction becomes increasingly more abundant as the n-BuA content of the copolymer is increased.All the products and principal features of the reaction are explained in terms of a radical process which is initiated by scission of pendant acrylate units and is propagated by a combination of depropagation and intra- and intermolecular transfer processes, the relative importance of which depends upon copolymer composition. Differences from the thermal reaction and the corresponding reaction in copolymers of methyl methacrylate and methyl acrylate are discussed.     

Polymer Architectures via Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization

Various versatile chain transfer agents (CTAs) have been synthesized for reversible addition fragmentation chain transfer (RAFT) polymerzation. Such CTAs have been used to modify hydroxyl containing materials and produce well-controlled molecular architectures such as amphiphilic copolymer from poly (ethylene glycol), AB block copolymer consisting of a biodegradable segment, poly (l-lactic acid) (PLLA) and grafted copolymers of poly (styrene), poly (methyl methacrylate) and poly (methyl acrylate) from cellulose.     

丙烯腈可控/"活性"自由基聚合研究进展

可控/"活性"自由基聚合能有效控制聚合物的分子量及其分布,并且能调控其微观拓扑结构。聚丙烯腈及其共聚物具有良好的成纤成膜性能,是一类应用十分广泛的聚合物。本文综述了可控/"活性"自由基聚合法合成聚丙烯腈及其共聚物的研究现状与进展,从氮氧自由基法(NMP)、引发转移终止剂法(iniferter)、原子转移自由基聚合(ATRP)和可逆加成-断裂链转移(RAFT)聚合等方面对丙烯腈均聚物和共聚物的合成研究作了全面的总结,提出了存在的问题,并且对今后的研究方向作了展望。     

Stereospecific reversible deactivation radical polymerization of biomass‐based acrylates for precise control of tacticity and molecular weight

Reversible deactivation radical polymerization (RDRP) of biomass‐based acrylates, (S )‐ and (R )‐2‐isopropyl‐5‐methylene‐1,3‐dioxolan‐4‐ones (S‐MiPDO and R‐MiPDO), was successfully performed to produce a well‐defined polymer with simultaneously controlled tacticity and molecular weight, and low dispersity (? < 1.3). In particular, meso triad (mm ) of the polymer was continuously controlled as designed from 28.1% to about 100% by changing the molar ratio of S‐MiPDO/R‐MiPDO in feed. In kinetic studies, the rate of RDRP was strongly influenced by the stereostructures of the propagating radical, and it was much lower in isospecific RDRP than atactic one in reversible chain transfer catalyzed polymerization (RTCP) in contrast to atom transfer radical polymerization (ATRP) where the rate would not change regardless of the tacticity. Increase of molecular weight and low ? of the polymer were also observed in reversible addition‐fragmentation chain transfer (RAFT) polymerization of MiPDO. In addition, block copolymers including stereoblock copolymers were feasibly synthesized by RTCP of styrene and methyl methacrylate using poly(MiPDO) prepolymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 445–456     

Influence of the microstructure of acrylic acid-n-butyl acrylate copolymers prepared by pseudoliving radical polymerization by the reversible addition-fragmentation chain transfer mechanism on their surface activity in aqueous solutions

The influence of the microstructure of acrylic acid-n-butyl acrylate copolymers prepared by pseudoliving radical polymerization by the reversible addition-fragmentation chain transfer mechanism on their surface activity in aqueous solutions was studied. The mechanisms of adsorption of polymer macromolecules on the phase boundary, accounting for the difference in the behavior of the random and block copolymers, were suggested. The dependence of the surface activity on the chain flexibility was elucidated. This dependence is very significant for the random copolymers and insignificant for the block copolymers.     

机理转移法合成星形梳状聚丁二烯-g-聚甲基丙烯酸甲酯共聚物的研究

结合活性负离子聚合与原子转移自由基聚合(ATRP),采用机理转移法制备了一系列窄分布且分子量可控的星形梳状聚丁二烯-g-聚甲基丙烯酸甲酯接枝共聚物(SC-(PB-g-PMMA)).首先通过阴离子聚合,制备星形聚丁二烯,后经甲酸-过氧化氢原位环氧化对链中部分双键进行环氧化,再与原位生成2-溴异丁酸发生酯化反应,得到具有链中活性溴的星形大分子引发剂(SPB-Brn).然后,利用该大分子引发剂,采用CuCl/CuCl2/PMDETA催化体系,通过ATRP聚合单体MMA,合成出星形梳状SC-(PB-g-PMMA)聚合物.通过GPC,1H-NMR和FTIR等分析手段对合成的星形大分子引发剂及星形梳状聚合物进结构表征,证实得到目标产物,并同时研究了聚合物的热力学性质与溶液性质.     

Two-Dimensional Chromatographic Analysis of Polystyrene-block-poly(methyl methacrylate) Copolymers Synthesized by Selective Oxidation of Polystrene-9-borabicyclo[3.3.1]nonane

Summary: The preparation of polystyrene block methyl methacrylate copolymers (PS-b-PMMA) is described. The polystyrene segment was prepared by anionic polymerization and the methylmethacrylate segment was prepared via free radical autoxidation of a borane agent attached to the styrene chain. 1 The chemistry involves a transformation of the anionic polymerization process to borane chemistry by firstly producing polystyrene with chain end unsaturated alkyl functional groups prepared using a n-butyllithium initiator and termination with allylchlorodimethylsilane. Secondly, the unsaturated macroinitiator end was hydroborated by 9-borabicyclo[3.3.1]nonane (9-BBN) to produce a borane terminated PS. Thirdly, the borane group at the chain end was selectively oxidized and converted to polymeric radicals in the presence of methyl methacrylate which then initiated radical polymerization to produce block copolymers. The polymer obtained was characterized using several chromatographic techniques including LC-CC (liquid chromatography under critical conditions) for the polystyrene segments and two-dimensional chromatography with LC-CC in the first dimension and SEC in the second. The results show that block formation was successful although significant homopolymerization of methyl methacrylate is also obtained.     

Gel effect in the bulk reversible addition–fragmentation chain transfer polymerization of methyl methacrylate: Modeling and experiments

A model for the evaluation of the kinetics and the chain length distribution in living/controlled radical polymerization mediated by reversible addition–fragmentation chain transfer (RAFT) in bulk is presented. Using the free volume theory, the model accounts for the diffusion limitations over both termination and RAFT exchange reactions. Model predictions are compared to experimental results of methyl methacrylate polymerization with cumyl dithiobenzoate as a RAFT agent. It is shown that the polymerization retardation observed in living systems at large conversions is well predicted. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1071–1085, 2006