Cosolvent effect of alkyl acrylates on the phase behaviour of poly(alkyl acrylates)-supercritical CO2 mixtures

Cloud-point data to 220 degrees C and 2000 bar are presented for ternary mixtures of poly(butyl acrylate)-CO2-butyl acrylate (BA) and poly(ethyl hexyl acrylate)-CO2-ethyl hexyl acrylate (EHA). The addition of either BA or EHA to the respective polymer-solvent mixtures decreases the cloud-point pressures by as much as 1000 bar and changes the pressure-temperature slope of the cloud-point curves from negative to positive which significantly increases the single-phase region. Both BA and EHA provide favourable polar interactions with the acrylate groups in the backbone of the polymer and they densify the solvent mixture. However, the effect of these cosolvents on the location of the cloud-point curves diminishes as the amount added to the solution increases. (C) 1998 Elsevier Science Ltd. All rights reserved.