Chain Propagation/Step Propagation Polymerization. 5. Telechelomer Polymerization via Alanine Mediation.

摘要

The)polyesterification of a monodisperse poly(oxyethelene-b-pivalolactone) telechelomer, having Mn of 2700 and containing hydroxyl and carboxyl end groups, is described. Polymerizations were attempted with no success using selected (a) activating agents, (b) dehydrating agents, and (c) esterification catalysts, wherein the reactions were monitored by size-exclusion chromatography, viscometry, and nuclear magnetic resonance. Success was achieved with titanium tetrabutoxide catalysis in the presence of alanine to give high molecular weight polymers. A 5-fold increase in viscosity was observed as the alanine-mediated polyesterification progressed, and the M(GPC) of the polymer obtained was 31,000. Reaction conditions could be optimized to avoid side reactions. The function of alanine in the esterification reaction is not yet clear; however, functions include (a) acting as a dehydrating agents, (b) acting as a template, and (c) increasing the effectiveness of titanium tetrabutoxide catalyst. Keywords: Chelates; Reprints. (aw)