Nonpolymerizable Monomers in Living Cationic Polymerization

将对1,1-二苯乙烯及相关高活性但不可聚合的单体加入活性阳离子聚合物的动力学和机理进行研究。电导测量和紫外可见光谱结合结构分析将确定动力学和加成方式，链端电离和解离的程度。还将研究二苯基正碳离子向单体加成的动力学，并确定自由离子和离子对的绝对速率常数。当第二个单体的反应活性高于第一个单体时，该结果将用于通过顺序添加单体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1,1-二苯乙烯）盖上一层，然后通过添加钛（IV）醇氧化合物、用较弱的酸取代刘易斯酸或使用普通离子盐来调整刘易斯酸以适应第二个单体的反应性。该提案的另一个目标是探索通过活性末端的原位功能化（末端猝灭）来合成末端功能聚合物。最后一个目标是研究活阳离子和活阴离子基团转移聚合的组合，以合成线性和杂臂星形嵌段共聚物。提出了基于1,1-二苯乙烯旋盖的两种不同方法；一种基于位点转化，另一种基于活性聚合物阳离子和阴离子的相互湮灭。这项研究提供了一种新的方法来合成各种结构明确的聚合物。这种聚合物是研究其基本物理性质作为结构函数所必需的。＊＊＊

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. ***