Chapter 5.1 – Polymerization in supercritical carbon dioxide: surfactants, micelle formation, and heterophase polymerization

This chapter describes polymerization in supercritical carbon dioxide. Due to their unique physical and chemical properties, supercritical fluids are at the center of interest for the processing of materials, plasticizing of polymers, in extraction processes, as well as solvent in polymerization reactions. The block copolymer chosen was poly(styrene-b-dimethylsiloxane) (PS-b-PDMS). PS serves here as CO2-phobic and PDMS as a CO2-philic part. The expected amphiphilic behavior should lead to micelle formation given the proper pressure and temperature range. Well defined latex particles of polyvinylpyrrolidone of about 1μm diameter with a small size distribution are produced. It is concluded that the particles were created in a stabilized reaction through the in sc-CO2 amphiphilic block copolymer PS-b-PDMS. As determined by light scattering experiments, the size of the micelles these amphiphilic molecules form at about the same experimental conditions is only 60 nm in diameter, much smaller than the product in the polymerization.