非线形嵌段共聚物的合成

主要介绍了非线形嵌段共聚物,如星型嵌段共聚物、杂臂星型共聚物、梳型聚合物等的合成方法,包括多官能团引发剂法、大分子引发剂法等。各种活性聚合方法,如阳离子开环聚合、原子转移自由基聚合(ATRP)和氮氧稳定自由基聚合等都可以用于合成非线形嵌段共聚物。     

基于苯氧基联烯的两亲性嵌段共聚物的合成

运用机理转换策略,结合自由基聚合和原子转移自由基聚合(ATRP),制备了含有聚联烯链段的两亲性三嵌段共聚物.设计合成了含有偶氮和ATRP引发基团的双官能团引发剂,先用该双官能团引发剂引发苯氧基联烯单体的自由基聚合,得到了含有ATRP引发基团的聚联烯大分子引发剂,然后该大分子引发剂引发亲水性单体N,N-二乙基氨乙基甲基丙烯酸酯(DEAEMA)的ATRP聚合,制得了聚N,N-二乙基氨乙基甲基丙烯酸酯-聚联烯-聚N,N-二乙基氨乙基甲基丙烯酸酯(PDEAEMA-b-PPOA-b-PDEAEMA).该三嵌段共聚物能在水溶液中形成胶束,通过荧光探针技术分别测定了它在不同离子浓度、不同p H值条件下的临界胶束浓度.实验结果表明,该聚合物胶束的cmc随着p H值增大而减小,随着离子浓度的增大而增大.     

PS-b-P4VP两嵌段共聚物的合成及其自组装的研究

双硫酯 (PhC(S)SCH2 Ph)作为链转移剂 ,AIBN作为引发剂 ,用可逆的加成 断裂链转移 (RAFT)活性自由基聚合方法 ,合成了PS大分子链转移剂 .然后在AIBN引发下 ,利用制得的大分子链转移剂 ,以DMF为溶剂 ,80℃下采用RAFT方法 ,合成了PS b P4VP两嵌段共聚物 ,通过核磁共振谱及动力学的研究证明了其活性聚合的特征 .结果表明聚合反应在 2 4h内转化率可达 95 % .并用透射电子显微镜 (TEM )和扫描电子显微镜(SEM)研究了PS b P4VP两嵌段共聚物在选择性溶剂硝基苯 四氢呋喃中的自组装行为 ,研究结果表明改变聚合物的浓度以及选择性溶剂 ,可观察到自组装行为的变化 .     

用稳定自由基聚合及光引发聚合制备嵌段共聚物

介绍了稳定自由基聚合的反应原理、引发剂设计，以及用稳定自由基聚合制备嵌段共聚物的几种方法：连续加料法、双官能团引发剂法和一步法。对于光引发聚合的原理及硫自由基的稳定性对聚合反应的影响也进行了讨论。     

原子转移自由基聚合在分子结构设计中的应用进展

原子转移自由基聚合(ATRP)是一种新型"活性"/可控聚合技术,可有效地实现对聚合物分子结构的设计,精准地控制聚合物分子结构。本文在介绍了官能团反应法、偶联反应法以及自由基聚合法制备ATRP大分子引发剂的基础上,进一步介绍了通过控制大分子引发剂"活性"点位置进行聚合物结构设计。同时还着重综述了大分子引发剂在嵌段聚合物、梳状聚合物、分子刷聚合物、树状及超支化聚合物和星形聚合物分子设计中的应用。     

用ATRP法和RAFT法制备线形嵌段共聚物

嵌段共聚物是将不同性质的聚合物连接在同一分子内，表现出特殊的性质，受到高分子科学家及工业部门的广泛关注。本文简要介绍了嵌段共聚物的结构、性能以及可能的应用。它有多种制备方法，这里着重介绍近年来通过原子转移自由基聚合(ATRP)和可逆加成-裂解链转移(RAFT)法制备嵌段共聚物的研究现状和进展情况。对于加料顺序、大分子引发剂末端基团、单体的反应活性以及大分子引发剂的引发效率、配体种类、大分子链转移剂的链转移常数等对嵌段共聚反应的影响也进行了讨论。     

支化PEG-b-PCL嵌段共聚合物的合成

以聚乙二醇甲基丙烯酸酯(PEGMA)为大分子引发剂进行ε-己内酯的酶催化开环聚合, 合成出嵌段共聚物, 然后将其转化成大分子引发剂型单体(Macroinimer), 最后通过原子转移自由基聚合(ATRP)制备出一种新型结构的嵌段型支化聚合物.     

“活”的α-甲基苯乙烯共聚物:聚合反应新化学和材料工程新技术

高于临界聚合反应温度时,α-甲基苯乙烯(AMS)单体和其聚合物处于聚合-解聚平衡.基于AMS聚合物在受热时可裂解生成大分子链自由基的特性,提出了含AMS结构单元的共聚物是一种"活"的,可作为大分子自由基引发剂的概念,并通过实验对AMS共聚物的引发性能和应用进行了研究.首先,合成了AMS与(甲基)丙烯酸酯类单体、丙烯酸、苯乙烯和马来酸酐等的共聚物.然后以上述共聚物为大分子引发剂,在90℃引发(甲基)丙烯酸酯类单体和苯乙烯等的本体聚合、溶液聚合和乳液聚合,得到了嵌段共聚物.用ESR谱证明了AMS的共聚物在加热时能裂解生成以碳原子为中心的大分子链自由基.此外,在聚合物的熔融共混中,AMS分解产生的大分子链自由基通过偶合反应形成接枝链,原位生成相容剂.AMS共聚物还可以对碳纳米管及无机粒子进行表面原位接枝改性.AMS共聚物是一类无小分子残留的绿色自由基引发剂,可以用于低成本制备两嵌段共聚物,也可以用于聚合物的熔融共混增容.     

用双硫酯链转移法合成嵌段聚合物

研究了以双硫酯为链转移剂进行的均聚和嵌段共聚物的合成 .首先合成大分子链转移剂 ,得到分子量可控、多分散性系数较小的均聚物PMMA、PBMA、PEMA、PEA、PBA、PMA、PSt,多分散性系数一般小于 1 30 .在相同的条件下 ,甲基丙烯酸酯类的聚合速度最快 ,苯乙烯其次 ,丙烯酸酯类最慢 .用末端带有双硫酯基团的PSt、PBMA、PBA为链转移剂 ,加入多种第二单体聚合得到实测分子量与理论分子量接近 ,且多分散性系数较小的两嵌段聚合物 .在链转移剂和引发剂的比例为 3∶1～ 6∶1的范围内 ,聚苯乙烯同样可以作为第一嵌段得到和其它酯类单体的两嵌段聚合物 .1 H NMR方法证明了聚合物的末端带有双硫酯基团 .嵌段聚合时必须加入微量的自由基引发剂以形成大分子自由基 ,达到较好的控制聚合效果     

用双硫酯链转移法合成嵌段聚合物

研究了以双硫酯为链转移剂进行的均聚和嵌段共聚物的合成。首先合成大分子链转移剂,得到分子量可控、多分散性系数（PDI）较小（＜1.30）的均聚物。用末端带有双硫酯基因的PSt,PBMA和PBA为链转移剂,加入第二单体聚合得到分子量可控、且PDI较小的两嵌段聚合物。嵌段聚合时必须加入微量的自由基引发剂以形成大分子自由基,达到较好的控制聚合效果。     

聚苯乙烯-b-聚硅氧烷-b-聚苯乙烯三嵌段共聚物的合成及表征

采用乙烯基封端的聚 (二甲基硅氧烷 )与溴化氢反应制得末端含有C Br的双官能聚 (二甲基硅氧烷 ) ,以此聚 (二甲基硅氧烷 )大分子为引发剂 ,CuCl为催化剂 ,4 ,4′ 二 (5 壬基 ) 2 ,2′ 联吡啶为配体 ,通过原子转移自由基聚合法 ,制得分子量和结构可控的聚苯乙烯 b 聚硅氧烷 b 聚苯乙烯 (PSt b PDMS b PSt)共聚物 .     

Synthesis of triblock copolymers based on two isomer acrylate monomers by atom transfer radical polymerization

The syntheses of triblock copolymers by the atom transfer radical polymerization of tert‐butyl and iso‐butyl acrylates as inner blocks with cyclohexyl methacrylate as outer blocks are reported. The living behavior and blocking efficiency of these polymerizations were investigated in each case. The use of difunctional macroinitiators led to ABA triblock copolymers with narrow polydispersities and controlled number‐average molecular weights. These copolymers were prepared from bromo‐terminated macroinitiators of poly(tert‐butyl acrylate) and poly(iso‐butyl acrylate), with copper chloride/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalytic system, at 40 °C in 50% (v/v) toluene solutions. The block copolymers were characterized with size exclusion chromatography and ¹H NMR spectroscopy. Differential scanning calorimetry measurements were performed to reveal the phase segregation. The glass transition of the inner block was not clearly detected, with the exception of the copolymer synthesized with the longest poly(iso‐butyl acrylate) macroinitiator length. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4828–4837, 2005     

Liquid crystalline block copolymers by sequential cationic or promoted cationic and free-radical polymerizations

The scope for the study of the synthesis and properties of liquid crystalline (LC) block copolymers is briefly outlined. While there are many approaches to the synthesis of LC block copolymers, the use of azo macroinitiators is very versatile and allows one to produce diverse block copolymer architectures. Azo macroinitiators are prepared by cationic or promoted cationic polymerization of tetrahydrofuran (1) or cyclohexene oxide (2), and are then used to initiate the free-radical polymerization of various methacrylates 3,4 or acrylates 5–9 containing mesogenic azobenzene or biphenyl units thereby yielding block copolymers. The AB or ABA block copolymers are microphase-separated and form smectic and/or nematic mesophases similar to the respective LC homopolymers.     

Styrene polymerization with some new macro or macromonomeric azoinitiators having peg units

Several new macroinitiators and macromerinitiators (macroinimers) were synthesized and evaluated for the bulk polymerization of sytrene at 60°C. Macroinitiators were prepared from the reaction of 4,4′-dicyano-4,4′ azovaleryl chloride ( 1 ) with poly(ethylene glycol) (PEG) with a M_ω of 400 and with either benzoyl chloride, acetyl chloride, phenyl isocyanate, or poly(ethylene glycol) oleyl ether. Macromer initiators were also prepared from the reaction of 1 with PEG having M_ω values of 200, 400, 600, 1000, or 1500 and with 4-vinylbenzyl chloride. The bulk polymerization of styrene by macroinimers gave crosslinked styrene-PEG block copolymers, while the polymerization by macroinitiators gave soluble copolymers. The molecular weights of the styrene-PEG block copolymers obtained with macroinitiators having either oleyl, benzoyl, or phenyl urethane end groups were 22000–29000 g/mol. DSC measurements showed that the crosslinked block copolymers had crystalline PEG units with melting transitions ranging from 11–37°C. © 1994 John Wiley & Sons, Inc.     

Synthesis and properties of polydimethylsiloxane-containing block copolymers via living radical polymerization

Polydimethylsiloxane (PDMS) block copolymers were synthesized by using PDMS macroinitiators with copper-mediated living radical polymerization. Diamino PDMS led to initiators that gave ABA block copolymers, but there was low initiator efficiency and molecular weights are somewhat uncontrolled. The use of mono- and difunctional carbinol–hydroxyl functional initiators led to AB and ABA block copolymers with narrow polydispersity indices (PDIs) and controlled number-average molecular weights (M_n's). Polymerization with methyl methacrylate (MMA) and 2-dimethylaminoethyl methacrylate (DMAEMA) was discovered with a range of molecular weights produced. Polymerizations proceeded with excellent first-order kinetics indicative of living polymerization. ABA block copolymers with MMA were prepared with between 28 and 84 wt % poly(methyl methacrylate) with M_n's between 7.6 and 35 K (PDI <1.30), which show thermal transitions characteristic of block copolymers. ABA block copolymers with DMAEMA led to amphiphilic block copolymers with M_n's between 9.5 and 45.7 K (PDIs of 1.25–1.70), which formed aggregates in solution with a critical micelle concentration of 0.1 g dm⁻³ as determined by pyrene fluorimetry experiments. Monocarbinol functional PDMS gave AB block copolymers with both MMA and DMAEMA. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1833–1842, 2001     

Synthesis and characterization of amphiphilic triblock polymers by copper mediated living radical polymerization

2-Dimethylaminoethyl methacrylate (DMAEMA) and 2-diethylaminoethyl methacrylate (DEAEMA) block copolymers have been synthesized by using poly(ethylene glycol), poly(tetrahydrofuran) (PTHF) and poly(ethylene butylenes) macroinitiators with copper mediated living radical polymerization. The use of difunctional macroinitiator gave ABA block copolymers with narrow polydispersities (PDI) and controlled number average molecular weights (M_n’s). By using DMAEMA, polymerizations proceed with excellent first order kinetics indicative of well-controlled living polymerization. Online ¹H NMR monitoring has been used to investigate the polymerization of DEAEMA. The first order kinetic plots for the polymerization of DEAMA showed two different rate regimes ascribed to an induction period which is not observed for DMAEMA. ABA triblock copolymers with DMAEMA as the A blocks and PTHF or PBD as B blocks leads to amphiphilic block copolymers with M_n’s between 22 and 24 K (PDI 1.24-1.32) which form aggregates/micelles in solution. The critical aggregation concentrations, as determined by pyrene fluorimetry, are 0.07 and 0.03 g dm⁻¹ for PTHF- and PBD-containing triblocks respectively.     

Poly(acrylate‐b‐styrene‐b‐isobutylene‐b‐styrene‐b‐acrylate) Block Copolymers via Carbocationic and Atom Transfer Radical Polymerizations

A series of polyacrylate‐polystyrene‐polyisobutylene‐polystyrene‐polyacrylate (X‐PS‐PIB‐PS‐X) pentablock terpolymers (X=poly(methyl acrylate) (PMA), poly(butyl acrylate) (PBA), or poly(methyl methacrylate) (PMMA)) was prepared from poly (styrene‐b‐isobutylene‐b‐styrene) (PS‐PIB‐PS) block copolymers (BCPs) using either a Cu(I)Cl/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) or Cu(I)Cl/tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) catalyst system. The PS‐PIB‐PS BCPs were prepared by quasiliving carbocationic polymerization of isobutylene using a difunctional initiator, followed by the sequential addition of styrene, and were used as macroinitiators for the atom transfer radical polymerization (ATRP) of methyl acrylate (MA), n‐butyl acrylate (BA), or methyl methacrylate (MMA). The ATRP of MA and BA proceeded in a controlled fashion using either a Cu(I)Cl/PMDETA or Cu(I)Cl/Me₆TREN catalyst system, as evidenced by a linear increase in molecular weight with conversion and low PDIs. The polymerization of MMA was less controlled. ¹H‐NMR spectroscopy was used to elucidate pentablock copolymer structure and composition. The thermal stabilities of the pentablock copolymers were slightly less than the PS‐PIB‐PS macroinitiators due to the presence of polyacrylate or polymethacrylate outer block segments. DSC analysis of the pentablock copolymers showed a plurality of glass transition temperatures, indicating a phase separated material.     

Polypropylene-block-poly(methyl methacrylate) and-block-poly(N-isopropylacrylamide) block copolymers prepared by controlled radical polymerization with polypropylene macroinitiator

Polypropylene-block-poly(methyl methacrylate) (PP-b-PMMA) and Polypropylene-block-poly(N-isopropylacryramide) (PP-b-PNIPAAm) block copolymers were successfully synthesized by radical polymerizations of MMA or NIPAAm with polypropylene (PP) macroinitiators. Polypropylene macroinitiators were prepared by a series of end functionalization of pyrolysis PP via hydroalumination, oxidation and esterification reactions. The PP macroinitiators thus obtained could initiate radical polymerizations of MMA or NIPAAm by using transition metal catalyst systems, and ¹H NMR analysis and gel permeation chromatography measurement confirmed the formation of PP-b-PMMA and PP-b-PNIPAAm block copolymers. In addition, the length of the incorporated PMMA or PNIPAAm segments in these block copolymers was controllable by the feed ratio between the monomer and the PP macroinitiator, and their molecular weights were estimated to be 35700 and 68700 (PMMA) and 1760 and 13300 (PNIPAAm), respectively. Transmission electron microscopy of the polymers obtained by NIPAAm polymerization revealed specific morphological features that reflected the difference of PNIPAAm segment length. The text was submitted by the authors in English.     

Synthesis and Characterization of Amphiphilic Poly(caprolactone) Star Block Copolymers

Summary: Novel, star‐shaped, amphiphilic block copolymers composed of fully degradable poly(caprolactone) were synthesized by sequential addition polymerization. In the first step, four‐arm macroinitiators were produced by ring‐opening polymerization of caprolactone by initiation with pentaerythritol. Then, block copolymers were synthesized by sequential addition of 4‐(2‐benzyloxyethyl)‐ε‐caprolactone to the four‐arm macroinitiators. Star‐shaped, amphiphilic block copolymers containing poly(caprolactone)‐block‐poly[4‐(2‐hydroxyethyl)caprolactone] segments were obtained by catalytic debenzylation.

Four‐arm amphiphilic polycaprolactone star block copolymer.     

Synthesis of new graft copolymers containing polyisobutylene by a combination of the 1,1‐diphenylethylene technique and cationic polymerization

The synthesis of macroinitiators for the cationic polymerization of isobutylene via radical polymerization is presented. The 1,1‐diphenylethylene system was used to obtain macroinitiators consisting of 4‐chloromethylstyrene and methyl methacrylate units. The resulting polymers were used for the cationic polymerization of isobutylene, yielding graft copolymers that were characterized by gel permeation chromatography and NMR. The dependence of the molar mass and polydispersity on the temperature and monomer concentration was studied. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3725–3733, 2002