Synthesis, characterization and properties of amphiphilic block copolymers of 2-hydroxyethyl methacrylate and polydimethylsiloxane prepared by atom transfer radical polymerization

Abstract

A series of amphiphilic poly(2-hydroxyethyl methacrylate)-b- polydimethylsiloxane-b-poly(2-hydroxyethyl methacrylate) (pHEMA-b-PDMS-b-pHEMA) (A-B-A) triblock copolymers were synthesized with varying block molecular weights. Control over the polymerization, micellar size and size distribution, dynamic mechanical properties, and film morphology of nine triblock copolymers was investigated as a function of block length. The polymerization resulted in copolymers with polydispersity index below 1.5. The self-assembly behavior of the triblock copolymers was studied in selective solvents for A and B blocks. The micellar diameter was determined by dynamic light scattering and transmission electron microscopy. The film morphologies were investigated by small angle X-ray scattering. Phase separation was observed when the blocks had similar molecular weights (symmetry). However, the ordering of the morphology was disrupted when the blocks lengths were asymmetric. Phase separation was observed by atomic force microscopy when the block molecular weights were symmetric. The viscoelastic properties were examined using dynamic mechanical analysis. The modulus and crosslink density increased with increasing pHEMA content. © 2012 The Society of Polymer Science, Japan (SPSJ) All rights reserved.