Stratifying polymer solutions in microsized pores: phase transitions induced by deformation of a porous material

Based on the thermodynamic approach, the influence of pore morphology on the phase equilibria in stratifying liquid solutions entrapped in a porous matrix is analyzed. As illustrated by an example of a solution of oligomeric fractions of polybutadiene and polystyrene, the matrix deformation determining the geometric characteristics of pores makes it possible to control the mutual solubilities of components and the volumes and thermodynamic stability of phases coexisting at equilibrium. The change in the geometric characteristics of pores in the general case is simulated by introducing a parameter that corresponds to the degree of deviation of the interface shape from the spherical one. Moreover, the behavior of the component solubilities as a function of pore volume is different in pores of different shapes, which is explained by various mechanisms of reducing the free energy of the system. With significant matrix deformations, the phase separation in microsized pores is suppressed and any solution compositions up to equimolar ones become.