A Polymer-Solvent System with Two Homogeneous Double Critical Points: Polystyrene (PS)/(n-heptane + methylcyclohexane)

摘要

Liquid-liquid (LL) critical demixing loci have been experimentally determined in the (T,P) projection for some polystyrene/solvent systems with nonspecific interaction for (approx 270 K < T < approx 500 K) and (0 MPa < P < 200 MPa). A lower homogeneous double critical pressure and lower homogeneous double critical temperature have been located for a solution of PS (M_#omega# = 2.0 * 10~6) dissolved in an n-heptane/methylcyclohexane mixture [PS-C_7H_(16)/CH_3C_6H_(11)//0.029/0.194/0.777 (wt. fractions)]. That solution forms the first example of a polymer/solvent with nonspecific interaction that exhibits two double critical points. A symmetrical representation of the LL critical loci in the (P,T) plane is developed.