Synthesis and Characterization of PE-b-POEGMA Copolymers Prepared by Linear/Hyperbranched Telechelic Polyethylene-Initiated ATRP of Oligo(ethylene glycol) Methacrylates

摘要

Amphiphilic diblock copolymers consisting of linear or hyperbranched polyethylene (PE) and poly[oligo (ethylene glycol) methyl ether methacrylate] (POEGMA) were synthesized via atom transfer radical polymerization (ATRP) initiated by PE macroinitiators (MIs). The MIs contained an end-capping 2-bromoisobutyryl group per chain. Their linear and hyperbranched structures were first synthesized through a "living" polymerization of ethylene under pressure of 27.6 and 1 atm, respectively, using Pd-diimine catalyst, [(ArN=C(Me)-(Me)C=NAr)Pd(CH_2)_3C(O)O(CH_2)_2OC(O)C(C H_3)_2Br]~+ SbF_6~- (Ar = 2,6-(iPr)2C_6H_3) (1). In the ATRP of OEGMA, the effect of solvent, ligand, and MI concentration on the block copolymer formation were studied. The macroinitiator and block copolymer samples were characterized by GPC, 1H NMR, and DSC measurements. All samples possessed well-defined topologies/structures with narrow molecular weight distributions and controlled lengths of PE and POEGMA blocks. The block structures were verified by an intrinsic viscosity study. Micelle formation and its temperature sensitivity were also analyzed by dynamic light scattering.