Polymer synthesis and processing using supercritical carbon dioxide

Carbon dioxide is a clean and versatile solvent for the synthesis and proce ssing of a range of materials. This review focuses on recent advances in po lymer synthesis and processing using liquid and supercritical CO2. The synt hetic techniques discussed include homogeneous solution polymerisation, pre cipitation polymerisation, dispersion and emulsion polymerisation, and bulk polycondensation. The formation of porous polymers and polymer blends is a lso considered, and the specific advantages of CO2 in these processes are e valuated in each case. The use of CO2 as a solvent for polymer processing i s reviewed from a materials perspective, with particular attention being gi ven to the formation of polymers with well defined morphologies. The variab le solvent strength associated with supercritical fluids has been utilised in areas such as polymer fractionation and polymer extraction. Plasticisati on phenomena have been exploited for the impregnation and heterogeneous che mical modification of polymeric materials. The formation of microcellular p olymer foams by pressure induced phase separation is considered, as is the use of CO2 for polymer particle formation, spray coating, and microlithogra phy. The aim of the review is to highlight the wide range of opportunities available to the materials chemist through the use of carbon dioxide as an alternative solvent.