Synthesis, Self-Assembly, and Thermosensitivity of Amphiphilic POEGMA-PDMS-POEGMA Triblock Copolymers

In this article, the synthesis and self-assembly of a novel well-defined biocompatible amphiphilic POEGMA-PDMS-POEGMA triblock copolymer were studied. The copolymer was synthesized by atom transfer radical polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) using alpha,omega-dibromo polydimethylsiloxane macroinitiator (Br-PDMS-Br). Br-PDMS-Br was synthesized through the esterification of alpha,omega-hydroxypropyl polydimethylsiloxane and 2-bromoisobutyryl bromide. The structures of the copolymers were confirmed by proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The copolymers showed reversible aggregation in response to temperature cycles with a lower critical solution temperature (LCST) between 61 and 66 degrees C, as determined by ultraviolet-visible spectrophotometry and dynamic light scattering. The LCST values increased in proportion to the length of the hydrophilic block and were lower than that of the POEGMA homopolymer. The self-assembly behavior of the copolymers in aqueous solution was investigated by fluorescence spectroscopy and transmission electron microscopy. The critical micelle concentration value (1.08-0.26 10(-6) mol L-1) decreased as the length of the POEGMA chain increased. The POEGMA-PDMS-POEGMA copolymers can easily self-assemble into spherical micelles in aqueous solution. Such biocompatible block copolymers may be attractive candidates as "smart" thermo-responsive drug delivery systems. (C) 2014 Wiley Periodicals, Inc.