Synthesis and colloidal behaviour of a polystyrene-b-poly(ethylene oxide) block copolymer

A convenient route was established for synthesizing a polystyrene-b-poly(ethylene oxide) block copolymer. Polystyryl lithium, prepared by initiating the polymerization of styrene with sec-butyl lithium, was end-capped by reaction with ethylene oxide. After isolation and characterization, the product was reacted with potassium methoxide to give a polymeric anion with a potassium counterion. The system was then used to initiate the polymerization of ethylene oxide to form the second block. Micellar aggregates formed by the polystyrene-b-poly(ethylene oxide) block copolymer in water were investigated by transmission electron microscopy using a phosphotungstic acid stain for the polyether component. Two types of colloidal particle differing greatly in average size were shown to be present in solution.