Macromonomer surfactants for the polymerisation of methyl methacrylate in supercritical CO2

Free radical polymerisation of methyl methacrylate in supercritical CO2 req uires addition of a surfactant (amphipathic macromolecule) to produce poly( methyl methacrylate) (PMMA) in high yield and molar mass and with well-defi ned particle sizes. This paper describes the use of poly(dimethylsiloxane)m onomethacrylate macromonomers in stabilising the free radical polymerisatio n of methyl methacrylate in supercritical CO2. In particular, the effects o f surfactant molar mass (2-10 kD) and concentration on the nature of the pr oduct PMMA are examined, It is found that the 2 kD surfactant is the most e ffective at low (wt./wt.) concentrations and may be a more viable option fo r industrial production than the higher molar mass surfactants, although th e particle sizes of the PMMA products are different. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.