Sulfonated Amphiphilic Block Copolymers: Synthesis, Self-Assembly in Water, and Application as Stabilizer in Emulsion Polymerization

Described is the synthesis of diblock copolymers generated via sequential atom transfer radical polymerization (ATRP) of poly(n-butyl acrylate) (PnBA) followed by chain augmentation with either sulfonated poly(2-hydroxyethyl methacrylate) (PHEMA) or poly(2-hydroxyethyl acrylate) (PHEA) blocks. ATRP of PHEMA or PHEA from PnBA macroinitiator was conducted in acetone/methanol 50:50 (v/v) and produced diblock copolymers of low PDI (< 1.3). Hydroxyl functional groups were converted to sulfonate through esterification using excess 2-sulfobenzoic acid cyclic anhydride (SBA). TEM images of aqueous block copolymer solutions reveal an array of polymer micelle morphologies including monodisperse spheres, cylinders, and cylinder aggregates. Surface tensions and critical micelle concentrations appear to be dependent more on hydrophile structure as opposed to its length. Application of the synthesized block copolymers as stabilizers for batch emulsion polymerization of n-butyl acrylate showed the polymeric surfactant effectively stabilizes latex particles and produces a lower polydispersity when compared with commonly applied commercial emulsifiers.