RAFT乳液聚合

高分子材料性能追本朔源主要由分子链微结构决定。以RAFT聚合为代表的"活性"/可控自由基聚合结合了传统自由基聚合和活性阴离子聚合各自的优点,提供了一种有效调控聚合物分子链微结构的聚合方法。RAFT乳液聚合作为"活性"/可控自由基聚合中具有工业应用前景的聚合方法,在过去二十年受到了学术界的广泛关注。本文总结了RAFT乳液聚合乳液失稳机理、聚合动力学、链结构的可控性等方面的进展。在此基础上,介绍了通过RAFT乳液聚合这一可控制备聚合物新材料的平台制备得到的新型嵌段共聚物、梯度共聚物,并展望了RAFT乳液聚合在高分子合成材料领域的应用前景。     

(甲基)丙烯酸氟烷基酯的“活性”/可控聚合

带氟烷基侧链的(甲基)丙烯酸氟烷基酯聚合物是一类具有独特表面性能和光学特性的氟聚合物,传统的自由基共聚合由于无法调节聚合物的微细结构和氟原子的分布,限制了该类聚合物在更广领域的应用.活性聚合为聚合物分子设计和合成提供了一个有效方法,利用活性聚合方法可以获得预期结构和性能的含氟嵌段聚合物材料.由于引入了氟烷基侧链,(甲基)丙烯酸氟烷基酯的活性聚合又有其特殊性,本文针对它的活性阴离子聚合、基因转移聚合、活性自由基聚合等方面作一综述.     

超分子聚合机理

与共价键聚合物由单体(M1)通过共价键连接不同,超分子聚合物是由单体(M2)通过非共价键连接而成的长链大分子。聚合包括分子聚合和超分子聚合。超分子聚合描述M2通过非共价键自组装形成超分子聚合物的过程,涉及氢键、π-π堆砌型和立体匹配等驱动力以及分子识别、协同性等特征,与M1通过共价键形成聚合物的过程(分子聚合)不同。为了理解超分子聚合物链结构形成机理,本文分析和讨论超分子聚合的三个主要机理:(1)线性链生长;(2)螺旋链生长;(3)拓扑链生长。     

原子转移自由基聚合在生物传感中的应用

原子转移自由基聚合(ATRP)是一种新颖的信号放大方法。在聚合过程中,成百上千个单体分子聚集形成长链聚合物,聚合物的侧链可以修饰丰富的功能基团,可与电化学或光学活性物质发生键合反应,从而显著增加单元生物分子识别反应信号分子的负载量,提高了检测灵敏度,实现了生物分子检测的信号放大。本文综述了ATRP的反应机理及其近年来在生物传感中的应用,并展望了其发展前景。     

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。     

茂金属催化剂分子“剪裁”新型异氰酸酯类聚合物

报导了用茂金属催化剂Ｃｐ‘ＭＣｌ２Ｌ或Ｃｐ’ＭＣｌＬ引发异氰酸酯活性聚合的研究及发展。讨论了催化剂的分子设计，可“剪裁”具有星型，梳型，间断蠕虫链，刚－柔－刚多嵌段及具有光学活性和液晶特性的新型异氰酸酯聚合物。同时还讨论了聚合反应和催化的动力学与链增长机理。     

基于叶立德同源聚合的聚烯烃功能化研究

近年来,新的合成方法的发现以及多种活性聚合组合策略的运用,已成为聚烯烃功能化领域的研究热点。本文首先对构筑聚烯烃分子链骨架的一种新合成方法--叶立德同源聚合的反应机理、单体及其研究现状进行了简要的介绍,然后详细评述了叶立德同源聚合分别与活性阴离子聚合、原子转移自由基聚合、可逆加成-断裂链转移聚合以及开环聚合相结合,设计、合成功能化聚烯烃共聚物的研究新进展。最后,对基于叶立德同源聚合设计、合成功能化聚烯烃共聚物的研究前景与实际应用进行了展望。     

控制/活性自由基聚合的进展

1活性自由基聚合1.1控制/活性自由基聚合自由基聚合是工业生产乙烯基类聚合物的重要方法。因其可聚合的单体种类多,能以水为介质进行悬浮和乳液聚合,反应温和,聚合工艺操作简便,重现性好,自20世纪50年代以来已成为工业生产高分子产品的重要技术。由于自由基聚合中增长链自由基很活泼,容易发生双分子偶合或歧化终止以及链转移反应,得到无活性的聚合物,聚合产物分子量分布宽、分子量和结构不可控制,从而影响聚合物的性能,需要改进。活性自由基聚合起始于20世纪80年代,在90年代取得了突破性进展,并成为当今高分子化学研究的热点之一。由于它能…     

P(NIPAM-co-NVP)共聚物分子链水溶液中的可逆聚集研究

用溶液聚合方法合成了线型聚(N-异丙基丙烯酰胺-co-N-乙烯基吡咯烷酮)共聚物,通过弹性光散射(elastic light scattering,ELS)、荧光光谱与动态光散射研究了共聚物水溶液分子链可逆聚集的温度和时间依赖性.研究表明,升温时,ELS强度增加,分子链聚集;降温时,ELS强度降低,聚集的分子链解离.荧...     

可逆加成-断裂链转移活性自由基聚合的应用研究进展

可逆加成-断裂链转移(Reversible addition-fragmentation chain transfer,RAFT)自由基聚合是活性自由基聚合领域的一次突破.由于该方法具有适用单体范围广、反应条件温和以及聚合实施方法多样等优点,已成为一种有效的分子设计和材料设计手段.它不但可实现聚合物链端及链段侧基的功能化和制备特定空间拓扑结构的大分子,比如嵌段、星型、梳状及链端氨基聚合物等,还可用于修饰固体材料表面及生物大分子来赋予其特殊的功能.本文综述了RAFT技术在实际应用中的实施研究进展.     

Polymerisation du trans pentadiene-1,3 par un amorceur soluble associant le triethylaluminium et l'orthotitanate de n-butyle—II: Structure et croissance des chaines polymeres

Study of the first compounds resulting from the insertion of trans 1,3 pentadiene into the titanium-carbon bond showed that only a small fraction of these bonds are active in polymerization and also that the geometrical isomerism of the by-products is a function of the ageing time of the catalytic system as for the polymer. Study of the polymer showed that the molecular distribution is wide and bimodal although the polymerization process is of a living type. Stereoregularity of the macromolecules is a growing function of the molecular weight. Long times of polymerization or high concentrations of catalyst lead to the formation of organic gel.     

基团转移聚合反应

本文介绍一种合成聚合物的新方法:基团转移聚合反应,它是以活性硅烷基化合物为引发剂在一定的催化剂存在下使α,β不饱和羰基化合物聚合成"活性聚合物",它可控制有一定分子量和较窄的分布。也可用于制备嵌段共聚物和遥爪聚合物。并介绍了新近的进展和它的应用。     

VOCl_3/Et_3Al_2Cl_3/CCl_4溶剂体系催化乙烯丙烯共聚

本文以VOCl_3/Et_3Al_2Cl_3为催化剂,在CCl_4溶剂中进行乙烯共聚反应。在聚合过程中,发生一异常的颜色突变现象。颜色突变后,体系催化聚合生成分子量很低的产物。从聚合物的结构表征及机理探讨表明:颜色突变后,体系产生了新的活性中心,催化机理发生了转变——由配位机理转变为阳离子机理。     

Branching kinetics of epoxy polymerization of 1, 4-butanediol diglycidyl ether with cis-1, 2-cyclohexanedicarboxylic anhydride

The copolymerization of an epoxy resin [1, 4-butanediol diglycidyl ether (DGEB) (Note a)] with an anhydride [cis-1, 2-cyclohexanedicarboxylic anhydride (CH)] in the presence of N, N-benzyldimethylamine (CA) as a catalyst produces a branched epoxy polymer. We show that the branching kinetics of the copolymerization reaction and the molecular weight distribution of the branched polymers can be approximated by using Smoluchowski's coagulation equation. In the simplest relevant application of this equation to our problem, the overall rate kernel w(u, v) that describes the branching probability in the equation turns out to be proportional to the sum of active sites on the two polymers with a time dependent coefficient. The molecular weight distribution (MWD) and the weight average molecular weight of the branched copolymers at different reaction stages before the gelation threshold are calculated theoretically. The calculated values are then compared with the experimental results obtained by using small angle X-ray scattering (SAXS), laser light scattering (LLS), and chemical analysis. Satisfactory agreement between experimental results and the use of the coagulation equation is attained when it is assumed that the distribution of epoxy polymer molecules is exponential in the number of branching points or, equivalently, active sites, at an early stage of the polymerization reaction.     

DEPENDENCE OF THE DISTRIBUTION OF ACTIVE CENTERS ON MONOMER IN SUPPORTED ZIEGLER-NATTA CATALYSTS

Distribution of active centers(ACD)of ethylene or 1-hexene homopolymerization and ethylene-1-hexene copolymerization with a MgCl_2/TiCl_4 type Z-N catalyst were studied by deconvolution of the polymer molecular weight distribution into multiple Flory components.Each Flory component is thought to be formed by a certain type of active center. ACD of ethylene-1-hexene copolymer with very low 1-hexene incorporation was compared with that of ethylene homopolymer to see the effect of introducingα-olefin on eth...     

Regularities of cationic polymerization of substituted aziridines

The cationic polymerization of some ordinary N- and C-substituted aziridines, initiated by the methyl etherate of boron trifluoride, shows a typical “temporarily living” character. Kinetic and spectroscopic data on the polymerization of N-methyl-aziridine under conditions under consideration as well as molecular mass characteristics of the polymers obtained, testify to the zwitter-ions as active centres of chain growth. This process is characterized by slow initiation, stationarity of propagation and slow termination with the participation of the polymer chain just after a monomer is used up. Such peculiarity of zwitter-ion polymerization allows to obtain liniar functional polyaziridines of given molecular mass by termination of the system by means of appropriate nucleophilic compounds.     

多核Nd-Al双金属配合物对丁二烯的聚合——Ⅰ.聚合物的分子量与微观结构间的关系及其聚合机理的讨论

在从均相稀土催化剂中分离出有聚合活性的Nd-Al双金属配合物的基础上,利用该配合物可单独引发丁二烯聚合的特点,较详细地研究了活性体浓度,外加烷基铝浓度,单体浓度以及聚合温度等因素对聚合产物分子量及微观结构的影响,确认二者之间存在着一定的内在联系,即分子量越高,顺式含量也越高;反之,分子量越低,顺式含量也越低。对此,本文提出了增长链对聚合过程起反作用的观点,从聚合机理的角度给予了解释。     

Development of studies devoted to design of polymer-immobilized catalysts

The state of the art in the field of designing metal-complex catalysts for olefin polymerization immobilized on polymer supports is analyzed. The types of polymers used for binding transition-metal compounds and organoaluminum components and the topochemistry of their distribution and transformations in the course of catalyzed reactions are considered. Polymer-immobilized bimetallic catalysts show promise in the catalysis of the polymerization process in which the key role of a macroligand is to unite active centers of various kinds. It has been shown that, in metallocene and postmetallocene catalysts, the same construction principles of immobilization are preserved as in the case of first-generation metal-complex catalysts. The possibility of isolating and studying active intermediates offered by the polymer support and the effect of immobilization on the molecular design of polymer systems are discussed.     

Evidence for several species of active sites in Ziegler-Natta catalysts

The kinetics of isoprene polymerization catalyzed by VCl₃ and Et₃Al were studied by measuring fractional conversions, polymer composition, and molecular weight distributions at a series of reaction times and temperatures. The rate of polymerization plotted against temperature shows an inflection point with a minimum and maximum in the 60–90°C range. The isomeric composition of the polymer changes with temperature but not with reaction time, while the molecular weight distribution undergoes substantial change with both of these variables. The rate of polymerization at sites producing low molecular weight polymers was measured, and the activation energy calculated to be about 10 kcal/mole. The active sites were found to deactivate at different rates. The results support the hypothesis that several species of active sites are present in the system and that these exhibit characteristic polymerization behavior.     

Solution Polymerization of Acrylonitrile Catalyzed by Sodium Triethylthioisopropoxyaluminate: A Polyacrylonitrile with High Structural Regularity

A new catalyst for the polymerization of acrylonitrile has been found by reacting sodium aluminum tetraethyl with a stoichiometric amount of oxygen, alcohols, or mercaptans, etc. The catalyst prepared by reacting NaAlEt₄ with RSH remains active at temperatures as low as ?78°C., polymerizing acrylonitrile into high molecular weight polymers with high conversions. At ?78°C., the propagating chain remains active over a period of days, and the chain length increases with time or conversion. At high conversions the molecular weight of the polymer is directly proportional to the concentration of the monomer, the catalyst concentration being kept constant. The efficiency of the catalyst expressed as the ratio of the number of the polymer molecules produced to the number of the sulfur atoms used is in excess of 80%. The weight-average molecular weight of the polymer measured by light scattering is roughly equal to the number-average molecular weight determined by sulfur analysis assuming only onesulfur atom in each polymer molecule. Although the data given here are only qualitative in nature, it is nevertheless evident that this system bears great resemblances to anionic polymerizations resulting in “living polymers.” The polymer obtained with the NaAlEt₃S(i-Pr) catalyst at ?78°C. differs from free-radical polyacrylonitrile in exhibiting substantially lower solubility, higher melting point, and higher rate of crystallization than that for the free-radical polymer. The polymer is also free from structural mpurities; it does not cause fluorescence in dilute solutions and has no absorption peak at 265 mμ; both these effects are produced by impurities in free-radical polyacrylonitrile. It is concluded that the polymer reported here is more regular in structure than free-radical polyacrylonitrile.