Phase Separation in Polymer Blends and Diblock Copolymers Induced by Compressible Solvents

The influence of compressed carbon dioxide sorption on the phase behavior of polymer blends and diblock copolymers exhibiting lower critical solution temperatures (LCSTs) and lower disorder-to-order transitions (LDOTs), respectively, was studied using in situ high-pressure small-angle neutron scattering. Homogeneous blends of poly(deuterated styrene) and poly(vinyl methyl ether) phase separate at temperatures more than 115 °C below the ambient pressure LCST upon sorption of less than 3.3 wt % CO 2 . The LDOTs in symmetric poly(deuterated styrene)- block -poly( n -butyl methacrylate) copolymers having total molecular weights of 78 000 and 32 000 g/mol are depressed by as much as 250 °C upon exposure to supercritical CO 2 at modest fluid-phase densities.