Synthesis and micellization of polydimethylsiloxane-carboxy-terminated poly(ethylene oxide) graft copolymer in aqueous and organic media and its application for the synthesis of core-shell magnetite particles

Abstract

An amphiphilic graft copolymer having an average of 7-8 carboxyester-terminated poly(ethylene oxide) grafted sequences on each polydimethylsiloxane main chain was obtained by a multistep procedure. Through fluorescence, surface tension and laser diffractometry methods the graft copolymer was proved to undergo micellization in aqueous media. In water, the critical micellization concentrations (CMC) are dependent on pH. Two CMC values were established for pH = 4, i.e. CMC1 = 1.01 g/L and CMC2 = 1.73 g/L corresponding to the transition from single chain to multiple chain micelles and to intermicellar aggregation, respectively. Between CMC1 and CMC2, the dimensions of micelles increased from 18 nm to 46 nm. The graft copolymer was proved to efficiently act as surfactant in the preparation of magnetite particles with a hydrophobic siloxane shell.