用大分子引发剂法制备嵌段共聚物

主要介绍了用大分子引发剂法制备嵌段共聚物的方法。大分子引发剂是从已商品化的功能聚合物制得或用其它活性聚合方法合成。从单封端的端羟基聚合物、其它单官能团或双官能团聚合物以及双功能基团缩聚物制得大分子引发剂．然后用于原子转移自由基聚合(ATRP)、氮氧稳定自由基聚合以及可逆加成裂解链转移(RAFT)聚合等．可制得结构可控、分子量分布窄的嵌段共聚物。     

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。     

用双官能团引发剂进行的基团转移嵌段共聚研究

本文用二种双官能团引发剂进行基团转移嵌段共聚研究,得到了一系列实测分子量和理论分子量相近、分子量分布较窄的A-B-A型嵌段共聚物。用GPC、~1H-NMR、DSC等手段对嵌段共聚物进行了表征,证明确是两相嵌段共聚丙烯酸酯。发现位阻较大的单体作为第二单体时不利于聚合。过高的催化剂用量使嵌段共聚的总转化率降低。使用极性较大的溶剂可缩短第一步聚合的诱导期,但不影响第二步聚合的诱导期,即极性较大的溶剂有利于催化剂的离解。单体浓度增大使共聚物的分子量减小,多分散性指数增大。可通过单体投料比改变共聚物的热形变温度。     

基于ATRP技术的多嵌段共聚物研究进展

原子转移自由基聚合(ATRP)技术是合成结构规整性聚合物的有效途径。综述了近十年来采用ATRP技术合成多嵌段共聚物的研究进展。从引发剂、共聚单体和反应条件等方面讨论了ABA型、ABC型和ABCBA型等类型多嵌段共聚物的合成、性质与潜在应用。对原子转移自由基聚合技术在合成功能性多嵌段共聚物中的应用前景进行了展望。     

基团转移嵌段共聚研究

本文采用双官能团引发剂和负离子型催化剂进行了甲基丙烯酸甲酯和甲基丙烯酸Ｃ７～９酯的基团转移嵌段共聚．讨论了温度、单体投料方式、引发剂－催化剂浓度比及单体浓度对聚合反应的影响，认为当两段反应温度分别为８５℃和２５℃时，引发剂浓度［Ｉ］＝１．３５×１０－２ｍｏｌ／Ｌ，催化剂引发剂浓度比［Ｃａｔ］／［Ｉ］＝０．１２６，以活性较低的Ｃ７～９ＭＡ为第一嵌段单体，有利于Ｃ７～９ＭＡ和ＭＭＡ的嵌段共聚．测定了嵌段共聚物的热形变温度；用ＧＰＣ对嵌段共聚物的相对分子质量及分布进行了表征，结合ＩＲ、１ＨＮＭＲ和热形变温度分析，证明所得到的为ＰＭＭＡ－ＰＣ７～９ＭＡ－ＰＭＭＡ均相三嵌段共聚物．     

基团转移聚合合成PMMA—PEA—PAN嵌段共聚物的研究

丙烯酸系橡胶的综合性能仅次于氟橡胶,成本较低,若制成可重复加工的热塑性弹性体则更有价值。前人曾用阴离子聚合法进行过合成试验,均因副反应太多等原因而未能获得满意的结果。基团转移聚合(GTP)是八十年代建立的合成高分子新方法,在室温下进行“活性聚合”是其重要特征。本文利用GTP方法、单官能团引发剂,仅通过适当控制加料次序和时机就合成了软段居中的三元共聚物,为合成全丙烯酸系热塑弹性体奠定了基础。     

一种含假芪型偶氮生色团两亲性嵌段共聚物的合成与表征

利用原子转移自由基聚合（ATRP）合成了一种新型的含假芪型偶氮生色团的两亲性嵌段共聚物P（HEMA-b-6CNAzo）。首先,采用ATRP引发剂引发三甲基硅保护的羟乙基甲基丙烯酸酯（HEMA—TMS）聚合,得到大分子引发剂P（HEMA—TMS）;接着进一步引发单体甲基丙烯酸6-（N_甲基苯胺基）己酯进行ATRP反应,得...     

原子转移自由基聚合制备聚(甲基丙烯酸甲酯-b-苯乙烯)时单体聚合顺序对嵌段效率的影响

采用原子转移自由基聚合研究了聚（ 甲基丙烯酸甲酯 ｂ 苯乙烯） 嵌段共聚物的合成,实验结果表明,当先进行甲基丙烯酸甲酯的聚合,然后再进行苯乙烯的聚合时,得到了完全的嵌段共聚物;反之,如果改变单体的聚合顺序,则嵌段效率很低．用聚合物末端Ｃ—Ｘ（Ｘ＝ Ｃｌ,Ｂｒ） 键的断裂能对实验结果进行了解释．     

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.     

原子转移自由基活性聚合合成PS-PMA-PS嵌段聚合物

本文采用氯化亚铜/α,α'-联吡啶配位化合物作催化剂.首先在130℃时用1-苯基氯乙烷在引发苯乙烯(St)进行原子转移自由基聚合,再以其产物PS-Cl作为大分子引发剂引发丙烯酸甲酯(MA)在反应温度为120℃时进行聚合,得到两嵌段聚合物PS-PMA-Cl.此两嵌段共聚物在特殊混合溶剂--丙酮/正丙醇(体积比7:3)中仍然可以作大分子引发剂引发苯乙烯进行原子转移自由基聚合,由于聚合体系接近于均相.所以表现出了较高的反应活性,并且合成的聚苯乙烯一聚丙烯酸甲酯一聚苯乙烯(PS-PMA-PS)三嵌段聚合物的分子量与设计值接近、分子量分布比较窄,反应的条件温和,可控性好.最后通过NMR技术对三元嵌段共聚物的结构迸行了表征.     

Copolymers of methyl methacrylate and fluoroalkyl methacrylates: Effects of fluoroalkyl groups on the thermal and optical properties of the copolymers

Fluoroalkyl methacrylates, 2,2,2‐trifluoroethyl methacrylate ( 1 ), hexafluoroisopropyl methacrylate ( 2 ), 1,1,1,3,3,3‐hexafluoro‐2‐methyl‐2‐propyl methacrylate ( 3 ), and perfluoro t‐butyl methacrylate ( 4 ) were synthesized. Homopolymers and copolymers of these fluoroalkyl methacrylates with methyl methacrylate (MMA) were prepared and characterized. With the exception of the copolymers of MMA and 2,2,2‐trifluoroethyl methacrylate ( 1 ), the glass transition temperatures (T_gs) of the copolymers were found to deviate positively from the Gordon‐Taylor equation. The positive deviation from the Gordon‐Taylor equation could be accounted for by the dipole–dipole intrachain interaction between the methyl ester group and the fluoroalkyl ester group of the monomer units. These T_g values of the copolymers were found to fit with the Schneider equation. The fitting parameters in the Schneider equation were calculated, and R² values, the coefficients of determination, were almost 1.0. The refractive indices of the copolymers, measured at 532, 633, and 839 nm wavelengths, were lower than that of PMMA and showed a linear relationship with monomer composition in the copolymers. 2 and MMA have a tendency to polymerize in an alternating uniform monomer composition, resulting in less light scattering. This result suggests that the copolymer prepared with an equal molar ratio of 2 and MMA may have useful properties with applications in optical devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4748–4755, 2008     

Synthesis and characterization of miniemulsion copolymers of methyl methacrylate (or styrene) and stearyl methacrylate

The copolymers of methyl methacrylate (MMA) (or styrene (ST))/stearyl methacrylate (SMA) obtained from miniemulsion polymerization were prepared and characterized. All the miniemulsions showed satisfactory colloidal stability upon aging due to the effectively retarded Ostwald ripening by the reactive costabilizer SMA. In subsequent miniemulsion copolymerizations, monomer droplet nucleation predominated in the particle formation process, but homogeneous nucleation could not be ruled out even at such high levels of SMA (20–50 wt.%). The contact angle first increased rapidly and then leveled off when the SMA content increased from 20 to 50 wt.% for both the copolymers of MMA/SMA and ST/SMA. At constant level of SMA, the copolymer of MMA/SMA with a less hydrophobic composition showed a larger contact angle compared to the ST/SMA counterpart. The contact angle (103 ± 1°) of the copolymer MMA/SMA (50/50 w/w) was comparable to that (104°) of PSMA. A schematic model was proposed to explain the experimental results.     

Biobased Polymers via Radical Homopolymerization and Copolymerization of a Series of Terpenoid-Derived Conjugated Dienes with exo-Methylene and 6-Membered Ring

A series of exo-methylene 6-membered ring conjugated dienes, which are directly or indirectly obtained from terpenoids, such as β-phellandrene, carvone, piperitone, and verbenone, were radically polymerized. Although their radical homopolymerizations were very slow, radical copolymerizations proceeded well with various common vinyl monomers, such as methyl acrylate (MA), acrylonitrile (AN), methyl methacrylate (MMA), and styrene (St), resulting in copolymers with comparable incorporation ratios of bio-based cyclic conjugated monomer units ranging from 40 to 60 mol% at a 1:1 feed ratio. The monomer reactivity ratios when using AN as a comonomer were close to 0, whereas those with St were approximately 0.5 to 1, indicating that these diene monomers can be considered electron-rich monomers. Reversible addition fragmentation chain-transfer (RAFT) copolymerizations with MA, AN, MMA, and St were all successful when using S-cumyl-S’-butyl trithiocarbonate (CBTC) as the RAFT agent resulting in copolymers with controlled molecular weights. The copolymers obtained with AN, MMA, or St showed glass transition temperatures (T_g) similar to those of common vinyl polymers (T_g ~ 100 °C), indicating that biobased cyclic structures were successfully incorporated into commodity polymers without losing good thermal properties.     

一种大分子引发剂的引发作用研究

将溶液聚合合成的α-甲基苯乙烯(AMS)和甲基丙烯酸缩水甘油酯(GMA)的低相对分子质量共聚物(计为PAG)作为大分子引发剂,分别研究了PAG引发单体甲基丙烯酸甲酯(MMA)和苯乙烯(St)的本体聚合反应,采用GPC和FTIR等手段对聚合产物进行了表征.研究结果表明,在加热到一定温度时,PAG具有引发作用,可以引发MMA和St进行本体聚合反应;聚合产物具有再引发功能,且其分子量与聚合物产率和聚合反应时间之间均有较好的线性关系.     

Controlled radical polymerization of anthracene‐containing methacrylate copolymers for stimuli‐responsive materials

Novel reversible networks utilizing photodimerization of crosslinkable anthracene groups and thermal dissociation were investigated. Reversible addition‐fragmentation chain transfer polymerization yielded well‐defined copolymers with 9‐anthrylmethyl methacrylate (AMMA) and other alkyl methacrylates such as methyl methacrylate (MMA) and 2‐ethylhexyl methacrylate (EHMA) having different AMMA compositions. Well‐controlled block copolymerization of AMMA and alkyl methacrylates was also successfully accomplished using a trithiocarbonate‐terminated poly(alkyl methacrylate) macro‐chain transfer agent. The anthracene‐containing copolymers showed reversibility via crosslinking based on photodimerization with ultraviolet irradiation and subsequent thermal dissociation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2302–2311     

Free-radical cross-linking polymerization of unsymmetrical divinyl compounds 2. Steric effect on gelation in the copolymerizations of allyl methacrylate with several alkyl methacrylates

As an extension of our continuing studies concerned with the free-radical cross-linking polymerization and copolymerization of multivinyl compounds, this article deals with the gelation in the copolymerization of allyl methacrylate (AMA), a typical unsymmetrical divinyl compound containing two types of vinyl groups such as methacryloyl and allyl ones having quite different reactivities, with several alkyl methacrylates, especially focusing on the steric effect of long-chain alkyl groups. Thus, AMA was copolymerized in bulk with methyl methacrylate (MMA), butyl methacrylate (BMA), lauryl methacrylate (LMA), and stearyl methacrylate (SMA) using azo-initiator at 50 °C in the presence of lauryl mercaptan as a chain transfer agent. The actual gel point was compared with the calculated one according to Stockmayer's equation by tentatively supposing equal reactivity of both vinyl groups. In the copolymerizations with LMA and SMA, the suppressed occurrence of intermolecular cross-linking reaction caused by the steric effect of long-chain alkyl groups was clearly observed as a reflection of delayed gelation, whereas the copolymerizations with MMA and BMA were roughly governed by the predominant occurrence of intermolecular cross-linking. These were supported by the conversion dependencies of the molecular-weight distribution profiles, the correlation curve of molecular weight versus elution volume, and the correlation of intrinsic viscosity versus molecular weight of resulting precopolymers.     

Graft Copolymerization of Pyrrolidone onto Copolymers of N-Acryloyl Pyrrolidone and Vinyl Monomers

The copolymerizations of N-acryloyl pyrrolidone (NAP) with vinyl monomers methyl methacrylate (MMA), acrylonitrile (AN) and acrylamide (AA) were carried out in dimethylformamide at 65°C using 2,2′-azobisisobutyronitrile(AIBN) as an initiator. The resulting copolymers were used as a polymeric initiator of the anionic graft copolymerization of 2-pyrrolidone. The percent grafting of 2-pyrrolidone onto vinyl copolymer backbone chain involving N-acyllactam groups was found best with copoly(NAP-co-MMA) when the KOH concentration was 0.03 M. The presence of crown ether increased the viscosity of graft copolymers and accelerated the initial rate of anionic graft copolymerization.     

Syntheses of graft and star copolymers possessing polyolefin branches by using polyolefin macromonomer

Graft and star copolymers having poly(methacrylate) backbone and ethylene–propylene random copolymer (EPR) branches were successfully synthesized by radical copolymerization of an EPR macromonomer with methyl methacrylate (MMA). EPR macromonomers were prepared by sequential functionalization of vinylidene chain‐end group in EPR via hydroalumination, oxidation, and esterification reactions. Their copolymerizations with MMA were carried out with monofunctional and tetrafunctional initiators by atom transfer radical polymerization (ATRP). Gel‐permeation chromatography and NMR analyses confirmed that poly(methyl methacrylate) (PMMA)‐g‐EPR graft copolymers and four‐arm (PMMA‐g‐EPR) star copolymers could be synthesized by controlling EPR contents in a range of 8.6–38.1 wt % and EPR branch numbers in a range of 1–14 branches. Transmission electron microscopy of these copolymers demonstrated well‐dispersed morphologies between PMMA and EPR, which could be controlled by the dispersion of both segments in the range between 10 nm and less than 1 nm. Moreover, the differentiated thermal properties of these copolymers were demonstrated by differential scanning calorimetry analysis. On the other hand, the copolymerization of EPR macromonomer with MMA by conventional free radical polymerization with 2,2′‐azobis(isobutyronitrile) also gave PMMA‐g‐EPR graft copolymers. However, their morphology and thermal property remarkably differed from those of the graft copolymers obtained by ATRP. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5103–5118, 2005     

Preparation and photochemical study of soluble optically active block copolymethacrylates and azo-containing random copolymethacrylates

A series of soluble optically active block copolymers of trityl methacrylate (TrMA) and cyclohexyldiphenylmethyl methacrylate (CHDPMA) with methyl methacrylate (MMA) and n-butyl methacrylate (n-BuMA) were synthesized using the complex of 9-fluorenyllithium and (S,S)-(+)-2,3-dimethoxy-1,4-bis(dimethylamino)butane as an initiator in toluene at −78°C. Soluble optically active random copolymers derived from TrMA and azo methacrylates, 6-(4-phenylazophenoxy)hexyl methacrylate (PAHM) and 2-(4-phenylazophenoxy)ethyl methacrylate (PAEM), were obtained under similar anionic polymerization conditions. Optical activities of the copolymers largely depended on the weight percentage of TrMA or CHDPMA component in the polymer chains. Solubility and film formability were significantly improved for the copolymers. Irradiation of optically active TrMA–MMA and CHDPMA–MMA block copolymer films containing photoacid, diphenyl-p-tolylsulfonium triflate, causes the partial hydrolysis of bulky esters and results in the conformational randomization of helical chains, which in turn leads to a significant change in optical rotation of the films. Photoisomerization studies of azo-containing random copolymers indicate that the trans to cis isomerization induces the helical conformation racemization in solution. © 1997 John Wiley & Sons, Inc.     

Synthesis and thermal dissociation of polymers having hemiacetal ester moieties

Polymers having hemiacetal ester moieties in the side chain were synthesized and their thermal dissociation was examined. 1‐Alkoxyethyl methacrylates (1) were synthesized from methacrylic acid with alkyl vinyl ethers and their radical copolymerizations with butyl methacrylate were carried out at 80°C for 6.5 h using AIBN as an initiator to afford the corresponding copolymers having the hemiacetal ester moieties in the side chain. The hemiacetal ester moieties in the copolymers thermally converted to carboxyl groups with elimination of the corresponding vinyl ethers. The thermal dissociation of the hemiacetal ester moieties in the side chain obeyed first‐order kinetics at 140°C, and their reactivities were in the following order: 1‐(tert‐butoxy)ethyl > 1‐isopropoxyethyl > 1‐ethoxyethyl > 1‐butoxyethyl ester. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 609–614, 1999