关键字：ENANTIOMERIC POLY(LACTIC ACID)S; STEREOCOMPLEX FORMATION; MECHANICAL-PROPERTIES; KINETIC RESOLUTION; MESO-LACTIDE; ORGANOCATALYSTS; STEREOCONTROL; ACETONITRILE; COMPLEXES; POLYMERS
摘要：Poly(lactic acid), as a kind of biocompatible and degradable polymer, has considerable potential in a wide range of applications. Because the main chain repeating unit has a chiral center, its physical and mechanical properties are closely related to its stereoregularity. In recent years, chiral organocatalysts have attracted increasing attention in stereoselective ring-opening polymerization (ROP) of lactide in addition to organometallic catalysts with chiral centers. In this contribution, we synthesized three types of chiral ureas (L-Phe-U, L-Ala-U and L-Val-U), which were prepared by reactions of L-Phenylalanine methyl ester (L-Phe-OMe), L-alanine methyl ester (L-Ala-OMe) and L-valine methyl ester (L-Val-OMe) with 4-(trifluoromethyl)phenyl isocyanate. They can form binary catalytic system with DBU, which can catalyze the stereoselective ROP of rac-lactide (rac-LA) to produce stereoblock PLA (P-m up to 0.87) at room temperature. In addition, the stereoregularity (P-m) can be improved by reducing the polymerization temperature with regularity as high as 0.90 at -20 degrees C. Using H-1 homonuclear decoupling spectroscopy, it was found that the contribution of chain-end control mechanism to stereo-regularity increased with decreasing temperature.
卷号：51
期号：10
是否译文：否