Synthesis and Characterization of Main Chain Ester-containing Poly (dimethylaminoethyl methacrylate) -based Copolymers

The main chain ester-containing poly (dimethylaminoethyl methacrylate) -based copolymers were successfully synthesized by the hybrid copolymerization of caprolactone (CL) and dimethylaminoethyl methacrylate (DMAEMA). The structure and properties of the resulting copolymers have been characterized by nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and so on. The results showed that the phosphazene base 1-tert-butyl-4,4,4-tris-(dimethylamino)-2, 2-bis [tris (dimethylamino)-phosphoranylidenamino]-2 A5, Lambda 5-catenadi-(phosphazene) (t-BuP4) displayed high activity for the copolymerization of CL and DMAEMA. The resulted copolymers consisting of CL and DMAEMA segments were random copolymers with only one glass transition temperature. The proportions of CL to DMAEMA in the copolymers were consistent with the feed ratios. The number average molecular weights of the resulted copolymers detected by GPC were in the range from 1. 63 x 10(4) to 2. 47 x 10(4), and the polydispersity (PDI) changed from 2. 11 to 2. 54. The introducing of hydrolytically cleavable ester endows the copolymer good degradability, but decreases the lower critical solution temperature (LCST) from 52. 6 degrees C to 44. 5. degrees C. The TEM result showed that the amphiphilic polymers could form micelles around 60 nm in water. This reported method provides a facile approach for preparing stimuli-responsive degradable polymers under mild conditions, and will be useful in bio-related applications.