Nonpolymerizable Monomers in Living Cationic Polymerization

点击翻译按钮获取中文摘要

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. ***