Effect of carbon dioxide sorption on the phase behavior of weakly interacting polymer mixtures: Solvent-induced segregation in deuterated polybutadiene/polyisoprene blends

The effect of carbon dioxide (CO₂) sorption on the lower critical solution temperatures of deuterated polybutadiene/polyisoprene blends was determined with in situ small-angle neutron scattering. CO₂ was a poor solvent for both polymers and exhibited very weak selectivity between the blend components. The sorption of modest concentrations of CO₂, at pressures up to 160 bar, induced phase segregation at temperatures well below the binary-phase-separation temperature and caused an increased asymmetry in the lower critical solution temperature curve. The origin of solvent-induced phase segregation in this weakly interacting polymer blend system was attributed predominantly to an exacerbation of the existing disparity in the compressibility of the components upon CO₂ sorption.