H3PO4‐induced micellization of styrene‐ethylene oxide block copolymers in toluene solutions

In toluene/dimethoxyethane (80/20)v solution, copolymers containing 11, 33, and 51 mol% of oxyethylene residues and having a fixed PS‐segment molecular weight of ~60,000 g/mol, are dissolved molecularly. Doping with 10, 20, and 50 mol% of H3PO4 based on the oxyethylene content, induces varying degrees, of micellization in the respective block copolymer solutions. Light scattering and viscometry were used to evaluate the relationship between block‐copolymer composition and the state of aggregation for solutions of styrene/ethylene oxide block copolymers as a function of solution concentration and level of doping with phosphoric acid. Specifically, diffusion coefficients, hydrodynamic radii, and critical micelle concentration were evaluated by dynamic light scattering. Radii of gyration were obtained by complementary static light scattering measurements. In all three block copolymers, complete micellization is realized at the 50 mol% H3PO4 doping level. At the 20 mol% H3PO4 doping level, complete micellization is induced with the copolymers containing 11 and 33 mol% of oxyethylene residues.