丙烯酰胺聚合物自由基聚合引发体系研究进展

丙烯酰胺类聚合物是应用较为广泛的水溶性高分子化合物,自由基聚合是大规模生产聚丙烯酰胺的有效方法。文章对自由基聚合偶氮类引发剂、氧化还原引发体系、复合引发体系的特点和研究应用进行了讨论,认为采用水溶性偶氮引发剂、含胺的氧化还原引发体系、含胺基功能性单体类引发剂等新型引发剂能制备高分子量的聚合物,合理设计新型复合引发体系可利于聚丙烯酰胺相对分子质量的进一步提高。     

超浓乳液聚合氧化还原引发体系的研究进展

介绍了超浓乳液的三个主要特点。从体系状态，单体含量，聚合速度，相对分子质量，聚合物形态和设备利用率方面比较了超浓乳液聚合与传统乳液聚合及本体聚合的区别。指出超浓乳液聚合中使用热分解引发剂所产生的问题及使用氧化还原引发剂的原因。还简单介绍了氧化还原引发体系的分类，回顾了前人在超浓乳液聚合工作中不同单体体系使用的氧化还原引发剂的情况，总结了不同单体体系中氧化剂还原剂的最佳配比，以及它们对动力学、相对分子质量的影响。最后展望了超浓乳液聚合新的发展方向。     

官能化有机锂引发剂技术发展

评述了官能化有纲单锂引发剂的技术进展以及在合成橡胶中的应用。指出该类引发剂今后研究的方向是一切引发活性高，烃溶解性好和能提高聚合物综合性能的有机锂化合物，同时开发官能化锂试剂比制备后即就地引发聚合的一体化反应技术。     

三官能度过氧化物引发制备HIPS树脂I．预聚合动力学

以多官能度过氧化物3,6,9－三甲基－3,6,9－三乙基－1,4,7－三过氧烷为引发剂,采用本体聚合法制备高抗冲聚苯乙烯,考察了各反应条件对预聚合动力学的影响。结果发现：聚合温度由125℃逐渐升高到145℃和引发剂质量分数由O．0075％增加到0．0200％时,聚合速率逐渐加快;当引发剂质量分数高于0．0200％时,聚合速率变化不大;随着基础胶质量分数由5％增加到15％和乙苯质量分数从10％增加到30％,聚合速率逐渐降低。不同引发剂引发聚合的效果与其官能度、半衰期及聚合温度等因素有关。     

UV固化塑料涂料中低迁移性光引发剂的研究进展

为了克服小分子光引发剂的弊端,尤其是迁移性问题,介绍了双官能度光引发剂、可聚合光引发剂、单组分夺氢型光引发剂、大分子光引发剂和可聚合单组分夺氢型光引发剂,在不同条件下光聚合动力学的研究表明,合成的光引发剂引发光聚合的性能不低于传统的小分子光引发剂。     

多官能度聚乙二醇的合成研究

以D-山梨醇为引发剂,二甲亚砜为溶剂,氢氧化钾为催化剂,环氧乙烷为单体,阴离子开环聚合合成了多官能度聚乙二醇。详细考察了催化剂、引发剂、溶剂、聚合温度等因素对聚合产物的性能影响。初步确定了聚合条件,聚合温度100～110℃,聚合时间6h。通过官能度的理论计算和测试证明合成的聚合物为多官能度聚乙二醇。     

三官能度过氧化物引发制备HIPS 树脂Ⅰ. 预聚合动力学

以多官能度过氧化物3,6,9-三甲基-3,6,9-三乙基-1,4,7-三过氧烷为引发剂,采用本体聚合法制备高抗冲聚苯乙烯,考察了各反应条件对预聚合动力学的影响.结果发现:聚合温度由125 ℃逐渐升高到145 ℃和引发剂质量分数由0.007 5% 增加到0.020 0% 时,聚合速率逐渐加快;当引发剂质量分数高于0.020 0% 时,聚合速率变化不大; 随着基础胶质量分数由5% 增加到15% 和乙苯质量分数从10%增加到30%,聚合速率逐渐降低.不同引发剂引发聚合的效果与其官能度、半衰期及聚合温度等因素有关.     

水溶性偶氮引发剂的合成与应用进展

总结了水溶性偶氮引发剂的分类、合成及应用现状.水溶液聚合和乳液聚合是自由基聚合机理重要的实施手段.它们使用环保水来做分散相,可采用水溶性的偶氮引发剂来进行聚合反应.研究表明,相比于油溶性的偶氮引发剂或常规的氧化还原引发体系,水溶性偶氮引发剂不论足在引发、聚合及产品特征方面都有明显的优势.最后对我国水溶性偶氮引发剂的发展...     

丙烯酸酯原子转移自由基聚合多官能引发剂

分别用乙二醇和三羟甲基丙烷与二氯乙酰氯反应合成了双(二氯乙酸)乙二醇酯和三羟甲基丙烷三(二氯乙酸酯),通过测定它们与单官能团引发剂2-氯乙酸乙酯共同引发的丙烯酸酯原子转移自由基聚合所得聚合物的相对分子质量和相对分子质量分布,证明它们分别是丙烯酸酯原子转移自由基聚合的四官能团和六官能团引发剂.     

双官能度单组分二苯甲酮类光引发剂的合成及引发活性研究

以4-（2-羟基乙氧基）二苯甲酮（4-BP）、丙烯酰氯和无水哌嗪为原料合成了一种双官能度单组分夺氢型光引发剂（4-BPAcPA）。通过红外光谱和核磁共振氢谱确认了结构;用UV分光光度仪研究了其紫外吸收、光解和迁移行为;用实时红外研究了光聚合动力学。结果表明：4-BPAcPA紫外吸收行为与4-BP相似,但摩尔消光系数是4-BP的2.17倍,光解速率快,迁移率仅为4-BP/EDAB体系的10%,引发HDDA效率的提高也意味着4-BPAcPA是一种能够单独引发体系聚合的高活性光引发剂。     

Analyzing the real advantages of bifunctional initiator over monofunctional initiator in free radical polymerization

Monofunctional initiators are extensively used in free radical polymerization. To enhance productivity, a higher temperature is usually used; however, this leads to lower molecular weights. Bifunctional initiators can increase the polymerization rate without decreasing the average molecular weight and this can be desirable. A bifunctional initiator is an important issue to be investigated, and it is of great interest to industries. The objective of this work is to study polymerization reactions with mono‐ and bi‐functional initiators through comprehensive mathematical models. Polystyrene is considered as case study. This work collects and presents some experimental data available in literature for polymerization using two different types of bifunctional initiators. Model prediction showed good agreement with experimental data. It was observed that the initial initiator concentration has a huge impact on the efficiency of initiators with functionality bigger than one and high concentrations of bifunctional initiator make the system behave as if it were a system operating with monofunctional initiator. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Bulk polymerization of styrene catalyzed by bi‐ and trifunctional cyclic initiators

A study of the bulk free‐radical polymerization of styrene in the presence of the cyclic bi‐ and trifunctional initiators cyclohexanone triperoxide, diethylketone triperoxide, acetone triperoxide, cyclohexanone diperoxide, and pinacolone diperoxide is reported. When these multifunctional initiators are used for styrene polymerization at high temperatures, it is possible to produce polymers with high molecular weights and narrow polydispersities at a high reaction rate. Additionally, the former initiators are used in a mixture that shows that the molecular parameters are influenced by the initiator concentration in the initiation system, in addition to the system employed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1–11, 2002     

双官能团引发剂引发甲基丙烯酸甲酯的聚合速率

研究了双官能团引发剂2,5-双(2-乙基己酰过氧化)-2,5-二甲基己烷（TX-141）引发甲基丙烯酸甲酯（MMA）的自由基聚合动力学,考察了引发剂浓度、聚合温度对聚合动力学的影响.结果表明：该体系的聚合活化能为91 kJ•mol^-1左右,计算得到TX-141引发剂的分解活化能为140 kJ•mol^-1左右,与实验值接近;TX-141引发剂的反应级数约为0.72,说明MMA聚合终止基元反应中单基和双基终止并存.同时与相似半衰期的过氧化二苯甲酰（BPO）比较,发现当TX-141引发剂浓度为BPO的1/2时,两者在各个聚合温度下的聚合动力学曲线几乎相同;但相对分子质量有明显增加,随聚合转化率增加,TX-141与BPO引发的聚合物数均分子量之比从1.2变化到1.33;由TX-141引发的聚合物低转化率时DSC曲线出现放热峰,而高转化率以及BPO引发的聚合物则没有.说明双官能团引发剂TX-141引发聚合时,在低转化率下TX-141引发剂的2个过氧键没有全部断裂,随聚合进行,断裂程度加深.     

Bifunctional initiators on the polymerization of vinyl acetate

Initiators with functionality bigger than one can be used in free radical polymerization (FRP) to increase the polymerization rate without decreasing the molecular weight of the polymer. The use of bifunctional initiators to produce linear polymers (like polystyrene and Poly(methyl methacrylate) (PMMA)) can be found in the literature; however, their application to produce branched polymers is rarer. This work reports the effect of the bifunctional initiator Luperox 531 (1.4‐bi(t‐butyl‐carboperoxide) cyclehexane) on the FRP of vinyl acetate, which produces branched polymers. The monofunctional initiator Luperox TBEC (tert‐butylperoxide‐2‐etyhexil carbonate) is also used as base of comparison. Polymerizations in ampoules have been performed in different temperatures and initiator concentrations. Results were compared to those obtained from the styrene polymerization, which produces linear chains. It can be concluded that the effect of bifunctional initiators on FRP depends strongly on the kinetic mechanism, kind of monomer, and operating conditions adopted. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Reversible crosslinking of polymers bearing pendant or terminal thiol groups prepared by nitroxide-mediated radical polymerization

Monomers or N-alkoxyamine initiators containing protected thiol groups are utilized to prepare polymers via nitroxide-mediated radical polymerization. Following thiol deprotection, the macromolecular properties of these polymers are manipulated, by adjusting the redox conditions to either form or cleave disulfide bonds, or irreversibly cap free thiols by the rapid addition to a maleimide Michael acceptor. Formation of disulfide bonds under dilute conditions results in intramolecular disulfide formation, resulting in internal polymer collapse. Alternatively, disulfide formation under high concentration results in intermolecular crosslinking of polymers to form networked macromolecular assemblies.     

Kinetics of the curing reaction of unsaturated polyester resins catalyzed with new initiators and a promoter

In this article, the curing of unsaturated polyester resins catalyzed with a promoter [cobalt(II) octoate] and free‐radical initiators is presented. The new initiators were formed by the oxidation process of ethyl methyl ketone or cyclohexanone with hydrogen peroxide and the mixture of solvents containing hydroxyl groups. As a reference, a typical curing system containing ethyl methyl ketone hydroperoxide (Luperox) and the promoter was used. The differential scanning calorimetry runs were performed at different heating rates. The experimental data were fitted with the empirical kinetic model. First, the kinetic parameters (activation energy, frequency factor, and reaction order) were obtained with a single reactive process and with the nth‐order reaction f(α), the nth‐order reaction f(α) with autocatalysis, and the first‐order reaction f(α) with autocatalysis. Second, two or three different reactive processes with the nth‐order reaction f(α) for each step were used. The obtained values of the activation energies for the curing of the unsaturated polyester resins with the free radical initiator–cobalt(II) salt catalytic system were in the range 40–60 kJ/mol for the polymerization initiated by the redox decomposition of the initiators and 80–90 kJ/mol for the polymerization initiated by the thermal decomposition of the initiators at high temperatures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1870–1876, 2006     

Experimental and theoretical study of the use of multifunctional initiators in the high impact polystyrene bulk process

The performance of three multifunctional peroxide initiators in a bulk high impact polystyrene (HIPS) process was experimentally and theoretically investigated. For the experimental work, a series of batch reactions was carried out, comprising the main stages of an industrial HIPS bulk process using multifunctional initiators with varying functionality and structure: DEKTP (cyclic trifunctional), PDP (cyclic bifunctional) and L331 (linear bifunctional). The theoretical work consisted of the development of a comprehensive, generic yet detailed mathematical model for bulk HIPS polymerization using multifunctional initiators. The model predicts the evolution of the main polymerization variables (including conversion, molecular weights, grafting efficiency) as well as the detailed molecular structure of the polymeric species (free polystyrene, residual polybutadiene and graft copolymer), and the melt flow index of the obtained HIPS. The model was adjusted and validated using experimental results, obtaining a good agreement between measured and predicted values. The model was used to theoretically evaluate the effect of the operating conditions on the molecular and physical characteristics of the obtained polymer. It was found that the use of multifunctional initiators leads to high polymerization rates and high molecular weights simultaneously, while promoting the grafting of styrene onto butadiene, generating a microstructure with salami‐type morphologies. POLYM. ENG. SCI., 58:198–212, 2018. © 2017 Society of Plastics Engineers     

基团转移聚合反应中的有机硅引发剂

评述了近年来基团转移聚合反应中几种常用的有机硅引发剂(如单官能团引发剂、双官能团引发剂、其它乙烯酮硅烷缩醛引发剂、大分子引发剂及其它含硅引发剂)的研究进展,并展望了基团转移聚合反应在高分子合成中的重要作用及应用前景。     

拉挤的引发系统

本文讨论了对拉挤引发剂的选择及联用，简单叙述了残余苯乙烯置的控制。     

Atom transfer radical polymerization (ATRP) of styrene and acrylonitrile with monofunctional and bifunctional initiators

A bifunctional initiator (benzal bromide) was used to initiate the bulk atom transfer radical polymerization of styrene and acrylonitrile at 90 °C with CuBr/2,2-bipyridyl. We compared these results with those of a monofunctional initiator of similar structure (1-bromoethyl benzene) under the same polymerization conditions. The monofunctional initiator worked better than the bifunctional initiator when both comonomers were added simultaneously at the beginning of the copolymerization; the bifunctional initiator was only effective when acrylonitrile was added after 20 min of polymerization with styrene. The styrene-acrylonitrile copolymers were characterized by gel permeation chromatography, ¹³C nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, and refractometry. Copolymer composition was monitored by both ¹³C NMR and by the change in the specific refractive index increment.