关键字：Ring opening polymerization;Biographies - Catalyst activity - Catalyst selectivity - Economic and social effects - Metabolism - Polyesters - Urea
摘要：Phosphazenes have attracted considerable attention in the field of ring-opening polymerization (ROP) of cyclic esters. However, the application of phosphazenes as catalyst is subject to a trade-off between activity and selectivity (chain propagation versus transesterification/back-biting reaction, e.g., controlled polymerization). Despite extensive research efforts, the development of a new catalytic system having concurrent high activity and selectivity remains a great challenge. In this work, we report that the binary organocatalytic system comprised of cyclic trimeric phosphazene base (CTPB) and ureas shows both of high activity and selectivity for the ROP of Ε-caprolactone (Ε-CL) and δ-valerolactone (δ-VL) in the presence of alcohol as initiator. It is found that the introduction of ureas would significantly increase the catalytic selectivity during ROP without sacrificing the catalytic activity of CTPB. Moreover, the polymerizations catalyzed by the title catalytic system exhibit immortal characteristics and thus thousands equivalent of monomer could be converted to polymer efficiently with desired MWs and microstructures. Linear diblock copolymer AB and star copolymers (AB)<inf>3</inf> with three identical diblock arms could be readily synthesized by sequential copolymerization using different alcohols as initiators.<br/> © 2018 Elsevier Ltd
卷号：111
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是否译文：否