Micellisation of polystyrene-b-polyglycidol copolymers in water solution

Abstract

The preparation of a set of amphiphilic polystyrene-b-polyglycidol (PS-b-PGL) diblock copolymers and their characteristics in aqueous media are described. The copolymers were prepared via anionic polymerisation starting from the synthesis of a polystyrene macroinitiator terminated by ethylene oxide, followed by anionic polymerisation of glycidol 1-ethoxyethyl ether to obtain a poly(1-ethoxyethyl glycidyl ether) block. The ethoxyethyl blocking groups of the hydroxyls were subsequently removed by hydrolysis. The copolymers differed in polymerisation degree of the polyglycidol block with DP values equal to 13, 43, 68 and 125, whereas the DP of polystyrene was 29. Two different organic media, N,N-dimethylformamide and dioxane, were used to prepare copolymer solutions dialysed afterward against water. The behaviour of diblock copolymers in water, their self-assembly and the size parameters of their aggregated structures were determined using dynamic light scattering. The critical micelle concentration (CMC) did not depend on the initial solvent and linearly increased with increasing content of hydrophilic glycidol units in the copolymer chain. However, above the CMC, the dispersions obtained from DMF contained a significant fraction of large aggregates. In the case of dioxane after dialysis, only one population of particles of the sizes, which can be related to typical core–shell micelles, was observed. Cryogenic transmission electron microscopy images revealed the presence of spherical objects and confirmed their sizes. PS-b-PGL micelles were highly stable and did not dissociate even after dissolution of their dispersions to concentrations below the CMC.