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。     

点击化学与活性自由基聚合联用构建特殊结构聚合物

点击化学由于其高效、可靠、高选择性等特点,一经提出便在复杂结构聚合物制备上得到广泛关注,而活性自由基聚合则具有聚合过程和聚合物结构可控等特点.本文综述了点击化学与活性自由基聚合方法如原子转移自由基聚合(ATRP),可逆加成断裂链转移聚合(RAFT),氮氧调控活性自由基聚合(NMP),以及原子转移氮氧自由基聚合反应(AT...     

4,4'-二甲氧基二苯基氮氧自由基调控甲基丙烯酸甲酯聚合

以4,4'-二甲氧基二苯胺为原料,过硫酸氢钾复合盐(Oxone)为氧化剂,通过一步反应合成了苯环类氮氧自由基——4,4'-二甲氧基二苯基氮氧自由基(DMDPN),并与引发剂偶氮二异丁腈(AIBN)组成双分子体系进行甲基丙烯酸甲酯(MMA)的调控聚合.用重量法测定转化率、凝胶渗透色谱(GPC)测定分子量及分布.研究了氮氧自由基/引发剂比以及聚合温度对聚合动力学和聚合物分子量及分布的影响,并对得到聚合物进行了再引发反应以及1H核磁共振表征.结果表明该体系下,氮氧自由基与增长自由基之间无明显的氢转移副反应发生,聚合过程中分子量随转化率线性增加,且聚合物末端具有活性,能进行再次链增长,体现出可控/"活性"自由基聚合的特点.确定了最佳氮氧自由基/引发剂摩尔比为1.6∶1、最佳聚合温度为120℃,并在70℃下实现了MMA的调控聚合.     

可控/“活性”自由基聚合制备聚乙烯及聚卤代烯烃

可控/“活性”自由基聚合(CLRP)可以用于制备分子量分布窄、分子链缺陷少的聚合物,如聚乙烯(PE)、聚氯乙烯(PVC)、聚偏氯乙烯(PVDC)和聚偏氟乙烯(PVDF),且易控制上述单体与其他单体共聚得到嵌段聚合物。本文调研了近年来可控/“活性”自由基聚合(如碘转移聚合(ITP)、氮氧稳定自由基聚合(NMP)、可逆加成断裂链转移(RAFT)聚合和金属催化的活性自由基聚合(OMRP)等)制备聚乙烯和聚卤代烯烃等方面的工作,并指出了未来的发展方向。     

N-叔丁基-α-苯基硝酸酮调控氯乙烯悬浮聚合

以过氧化新癸酸α-异丙苯酯(Lup188)作为引发剂,聚乙烯醇(PVA)和羟丙基甲基纤维素(HPMC)作为复合分散剂,加入N-叔丁基-α-苯基硝酸酮(PBN)用氮氧自由基在40～70℃下调控氯乙烯(VC)悬浮聚合.PBN能有效控制聚氯乙烯链增长,聚合后期无自加速现象,体现出可控/"活性"自由基聚合的特点.用重量法测定转化率、GPC测定聚合物分子量与分布,研究了引发剂用量、PBN用量以及聚合温度对聚合动力学和聚合物分子量及分布的影响.得到该聚合体系下VC、Lup188、PBN的最佳摩尔配比为10000∶7∶1,最佳聚合温度为50℃,将转化率控制在50%以下时,能得到较窄分子量分布的聚氯乙烯产物.     

超分子聚合物制备新方法:超分子单体的共价聚合

超分子聚合物是超分子化学与高分子化学交叉的前沿研究领域,近年来受到了国内外研究学者的广泛关注.可控制备超分子聚合物对于研究超分子聚合物的结构与性能关系、设计合成特定功能的超分子聚合物具有重要的意义.本文将总结通过超分子单体的共价聚合反应以制备超分子聚合物的方法.不同于传统的制备超分子聚合物的方法,超分子单体的共价聚合方法将不易调控的非共价聚合转化为可控的共价聚合,为实现超分子聚合物的可控制备提供了新思路.     

光调控的活性自由基聚合的研究新进展

从引发和催化两个方面概述了光辐照在活性自由基聚合(LRP)中的应用,从机理上详细地分析了光辐照对氮氧调控自由基聚合(NMP)、原子转移自由基聚合(ATRP)、可逆加成-断裂链转移自由基聚合(RAFT)以及有机钴催化的可控自由基聚合反应(CMRP)的影响。与传统自由基聚合相比,光调控的活性自由基聚合方法可在温和的条件下生成自由基,能够克服传统LRP的一些缺陷,如降低催化反应活化能、提高聚合物末端官能度等。同时,本文对光调控反应的进一步应用以及新方法的产生也进行了展望。     

5,6-苯并-2-亚甲基-1,3-二氧环庚烷的活性自由基开环聚合反应

活性 (或称可控 )自由基聚合研究是目前高分子科学的研究热点之一[1～ 8] .活性自由基聚合制备的聚合物具有分子量随转化率提高而线性增加、分子量分布窄和聚合反应为一级反应动力学等特点 .自由基开环聚合所得产物体积收缩小 ,某些含有不饱和双键的螺环单体发生双开环聚合时甚至发生体积膨胀 ;开环聚合还可在聚合物主链上引入各种官能团 ,如酯基、碳酸酯基、酮基等 [9～ 12 ] .因此 ,用活性聚合的方法对自由基开环聚合的分子量和分子量分布进行控制 ,可以制备出具有各种不同结构和性能的新聚合物 . Wei等 [13] 报道了利用稳定自由基法实现…     

DEPN调控自由基聚合研究进展

氮氧自由基调控聚合是通过在氮氧自由基与增长链自由基之间建立一种动态的热力学可逆平衡来控制聚合反应动力学和聚合产物的分子量及其分布的聚合方法。SG1的出现拓展了氮氧自由基调控聚合（NMP）的研究领域,从聚合体系的扩展到动力学研究的深入,进一步完善了聚合反应动力学调控理论的基础研究,确立了实验条件及影响因素。本文主要综述了...     

含糖聚合物可控合成研究进展

活性聚合技术的进步,使设计合成结构可控的含糖聚合物成为可能.本文介绍了阴离子聚合、阳离子聚合、原子转移自由基聚合、可逆加成断裂链转移聚合、硝基氧介导聚合、开环聚合和开环易位聚合等一系列可控/"活性"聚合技术在合成含糖聚合物中的应用,并对这一领域所取得的研究进展及现状进行了综述.     

Synthesis and study of novel polyol‐bound photosensitizers for cationic UV‐curable systems

Novel cationic intramolecular hydrogen abstraction photosensitizers (IHA‐PSs) based on a proposed intramolecular hydrogen abstraction photosensitization (IHAP) mechanism were synthesized and found to have a pronounced photosensitization effect in cycloaliphatic epoxide based cationic UV‐curable systems using sulfonium salt photoinitiators. A series of polyol‐based photosensitizers were synthesized with naphthalene attached. One photosensitizer, P‐Na, was found to have a more pronounced photosensitization effect in three different formulation systems, as revealed by real‐time Fourier transform infrared and differential photocalorimetry experiments. Such a phenomenon can be explained by a proposed facile IHAP mechanism, which is possible only with the unique molecular structure of P‐Na. The effect of P‐Na was further confirmed by comparison with two non‐polyol‐type photosensitizers. A designed IHA‐PS molecule was synthesized with the proposed principles ofthe IHAP mechanism, and it achieved a photosensitization effect similar to that of P‐Na with a much lower molecular weight and fewer hydroxyl groups per molecule. This further validated the proposed IHAP mechanism. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4435–4449, 2006     

Quasiliving Carbocationic Polymerization. X. Molecular Weight Averages and Polydispersity

In quasiliving polymerizations with reversible chain transfer (QL_0R systems), polymers with narrow molecular weight distribution can be obtained, It has been shown that while in true living systems (L₀₀) R = 1, and in quasiliving systems with irreversible chain transfer (QL₀₁) R = 2 is the limiting value of polydispersity, in QL_0R systems r = 4/3 is the polydispersity to which the distribution of the polymer tends with increasing polymerization time. This limit is independent of the rate of reinitiation; the course of the R vs t curves is, however, determined by the various rate constants.     

A quinoxaline derivative as a long wavelength photosensitizer for diaryliodonium salts

This article reports the use of a quinoxaline derivative as a photosensitizer for diaryliodonium salt photoinitiators. 2,3‐bis(3,4‐bis(decyloxy)phenyl)‐5,8‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)quinoxaline (DOPEQ), is a highly conjugated compound with strong absorption bands at wavelengths ranging from 300 to 550 nm and is shown to facilitate photoinitiated cationic polymerization of heterocyclic monomers such as oxiranes and oxetanes. The polymerizations are initiated at room temperature by using long wavelength UV light in the presence of diphenyliodonium hexafluorophosphate (Ph₂I⁺PF). The polymerizations are monitored by optical pyrometry (OP). It is also possible to initiate photopolymerizations with ambient solar irradiation in the presence of this photosensitizer dye. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 209–213, 2010     

Dibenzophenazine derivatives as visible photosensitizers for diaryliodonium salts

The use of two dibenzo[a,c]phenazine derivatives, 10,13‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)dibenzo[a,c]phenazine and 10,13‐bis(4‐hexylthiophen‐2‐yl)dibenzo[a,c]phenazine are reported as photosensitizers for diaryliodonium salt photoinitiators. Novel dyes based on the dibenzo[a,c]phenazine skeleton are shown to be efficient in carrying out the cationic photopolymerizations. Representative examples of different types of monomers including epoxide, and vinyl monomers are polymerized in the presence of the photosensitizers and diphenyliodonium hexafluorophosphate (Ph₂I⁺PF). Polymerizations are initiated at room temperature using long wavelength UV and visible light, and monitored by optical pyrometry. The photopolymerization of an epoxide monomer via solar irradiation is also demonstrated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Indian Turmeric and its Use in Cationic Photopolymerizations

Curcumin, an intensely yellow dye isolated from Indian turmeric is an excellent electron-transfer photosensitizer for cationic vinyl and ring-opening polymerizations. Especially attractive features of curcumin are its strong absorption, broad spectral sensitivity, efficient electron-transfer, low toxicity and low cost. Using curcumin as a photosensitizer, the cationic photopolymerizations of a variety of monomers were carried out including such naturally derived monomers as epoxidized terpenes and epoxidized vegetable oils. The impact of this technology on applications such as housing, boat-building and water distribution is discussed.     

Benzotriazole derivatives as long wavelength photosensitizers for diaryliodonium salt initiators

Two benzotriazole derivative dyes 4,7‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)‐2‐dodecyl‐2H‐benzo[1,2,3]triazole, and 2‐dodecyl‐4,7‐bis(4‐hexylthiophen‐2‐yl)‐2H‐benzo[d][1,2,3]triazole are shown to work as efficient photosensitizers for a diphenyliodonium salt initiator in cationic photopolymerization of epoxide and vinyl monomers. Substituted thienyl groups are attached to benzotriazole backbone to extend conjugation and enhance electron density of the molecules. Thereby, it was possible to initiate polymerizations at room temperature using long wavelength UV and visible light. The progress of photopolymerizations was monitored using optical pyrometry. The photopolymerization of an epoxide monomer using solar irradiation was also demonstrated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Phenothiazine photosensitizers for onium salt photoinitiated cationic polymerization

Phenothiazine compounds bearing a wide range of different substituents are excellent photosensitizers for onium salt cationic photoinitiators. These photosensitizers are generally operative in the mid‐ and long‐range regions of the UV spectrum and are especially useful for enhancing the rate of photoinitiated cationic polymerization carried out utilizing both filtered and broadband UV emission sources. In this article, the syntheses of several different substituted phenothiazines are described and the ability of these compounds to photosensitize the photolysis of different onium salt photoinitiators is evaluated. Attempts were made to correlate the structure and spectral characteristics of the phenothiazines with their efficiency of photosensitization in the cationic photopolymerizations of several typical epoxide and vinyl ether monomers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1187–1197, 2001     

Photocationic and radical polymerizations of epoxides and acrylates by novel sulfonium salts

Novel sulfonium salts [methyl‐, 2‐indany‐, or 1‐ethoxycarbonylethyl methyl‐2‐naphthylsulfonium hexafluorophosphate and 2‐indany‐, 1‐ethoxycarbonylethyl‐, 2‐methyl‐2‐phenylpropyl‐, 2‐phenylpropyl‐, 2‐phenylethyl‐, 2‐(4‐methoxyphenyl)‐ethyl‐, or 3‐(4‐methoxyphenyl)‐2‐propyl methylphenylsulfonium hexafluorophosphates] were synthesized by the reaction of dimethylsulfate and the corresponding sulfides followed by anion exchange with KPF₆. These sulfonium salts could polymerize epoxy monomers at lower temperatures than previously reported for benzylsulfonium salt initiators. In particular, sulfonium salts with naphthyl groups showed higher photoactivity than already reported for di(4‐tert‐butylphenyl)iodonium and triphenylsulfonium hexafluorophosphates. These sulfonium salts showed higher activity in photoradical polymerization and photocationic polymerization. The photopolymerization was accelerated by the addition of 4‐methoxy‐1‐naphthol, N‐ethylcarbazole, 2,4‐dimethylthioxanthone, phenothiazine, and 2‐ethyl‐9,10‐dimethoxyanthracene as photosensitizers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3816–3827, 2003     

Novel pyridinium salts as cationic thermal and photoinitiators and their photosensitization properties

Novel pyridinium salts [N‐(α‐phenylbenzyl)‐, N‐(1‐naphthylmethyl)‐, or N‐cinnamyl p‐ or o‐cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of p‐ or o‐cyanopyridine and the corresponding bromides followed by anion exchange with KSbF₆. These pyridinium salts polymerized epoxy monomers at lower temperatures than previously reported for N‐benzyl‐2‐cyanopyridinium hexafluoroantimonate. The o‐substituted pyridinium salts showed higher activity than the p‐substituted ones, and the crosslinked epoxy polymers cured with these initiators showed higher glass‐transition temperatures. These pyridinium salts photoinitiated radical polymerization as well as cationic polymerization. The photopolymerization was accelerated by the addition of aromatic ketones as photosensitizers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1037–1046, 2002     

Curcumin: A naturally occurring long‐wavelength photosensitizer for diaryliodonium salts

Curcumin, a naturally occurring, intensely yellow dye extracted from the spice turmeric, is an efficient photosensitizer for diaryliodonium salt photoinitiators at wavelengths ranging from 340 to 535 nm. With curcumin as a photosensitizer, it is possible to carry out the cationic photopolymerization of a wide variety of epoxide, oxetane, and vinyl monomers with long‐wavelength UV and visible light. An example of the photopolymerization of an epoxide monomer with ambient solar irradiation is provided. Several other curcumin analogues were synthesized, and their use as photosensitizers is examined. With such photosensitizers, the range of spectral sensitivity can be extended well into the visible region of the electromagnetic spectrum. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5217–5231, 2005