High Conversion Catalytic Chain Transfer Polymerisation of CO{sub}2-Expanded Methyl Methacrylate

摘要

Experimental molecular weight distributions are presented for the catalytic chain transfer polymerisation of CO{sub}2-expanded methyl methacrylate at 50°C in the range of 1 to 25% conversion. The effect of poly(methyl methacrylate) on the volumetric expansion of the monomer with CO{sub}2 is considered. At 5 MPa, the weight average molecular weight increases with conversion while the polydispersity index increases slightly. At 6 MPa, the reaction proceeds above the homogeneous expansion limit, as indicated by a cloudy appearance in the liquid phase. Under these conditions, a double-peak molecular weight distribution is obtained, leading to contamination of the oligomer with high molecular weight product. These observations highlight the need for accurate determination of the phase behaviour of the reaction system.