Nonpolymerizable Monomers in Living Cationic Polymerization

9502777将对1，1-二苯基乙烯和相关的高反应性但不可聚合的单体添加到活性阳离子聚合物中进行动力学和机理研究。 电导测量和紫外-可见光谱结合结构分析将确定添加的动力学和模式，链端电离和解离的程度。 还将研究二苯基碳正离子加成到单体中的动力学，并确定自由离子和离子对的绝对速率常数。 当第二单体的反应活性高于第一单体的反应活性时，该结果将用于通过顺序单体加成合成定义明确的嵌段共聚物。 该方法包括用反应性但不可聚合的单体如1，1-二苯基乙烯封端，然后通过加入烷氧基钛（IV）、用较弱的路易斯酸代替刘易斯酸或通过使用常见的离子盐使刘易斯酸性适应第二单体的反应性。 该提案的另一个目的是探索通过活性末端的原位官能化（末端淬灭）来合成末端官能化聚合物。 最后一个目标是研究活性阳离子和活性阴离子基团转移聚合的组合，用于合成线性和杂臂星星嵌段共聚物。 基于1，1-二苯基乙烯封端，提出了两种不同的方法;一种基于位点转换，另一种基于活性聚合物阳离子和阴离子的相互湮灭。 这项研究为合成具有精确已知结构的各种定义明确的聚合物提供了一种新方法。 需要这种聚合物来研究作为结构函数的基本物理性质。 ***

9502777 Faust Kinetic and mechanistic studies on the additions of 1,1- diphenylethylene and related highly reactive but non- polymerizable monomers to living cationic polymers will be carried out. Conductance measurement and UV-vis spectroscopy combined with structure analysis will determine the kinetics and mode of addition, the extent of chain end ionization and dissociation. The kinetics of the addition of diphenylcarbenium ions to monomers will also be studied, and the absolute rate constants will be determined for free ions and ion-pairs. The results will be used in the synthesis of well-defined block copolymers by sequential monomer addition when the reactivity of the second monomer is higher then that of the first monomer. The method involves capping with a reactive but non-polymerizable monomer such as 1,1-diphenylethylene, followed by tailoring the Lewis acidity to the reactivity of the second monomer by the addition of titanium(IV) alkoxide, by replacing the Lewis acid with a weaker one or by the use of a common ion salt. Another objective of the proposal is to explore the synthesis of end-functional polymers by in-situ functionalization (end-quenching) of the living ends. The last objective of the proposal is to investigate the combination of living cationic and living anionic-group transfer polymerization for the synthesis of linear and hetero-arm star block copolymers. Two different methods are proposed based on 1,1-diphenylethylene capping; one based on site transformation and the other based on mutual annihilation of the living polymer cations and anions. %%% This research provides a novel approach to the synthesis of various well-defined polymers with precisely known architecture. Such polymers are needed to study the fundamental physical properties as a function of structure. ***