Polymer drying. IV. A molecular interpretation of polymer drying

Further consideration of data already collected, in many time-studies that monitored gravimetrically evaporations of acetone, toluene, and chloroform from the corresponding liquid-saturated poly(styrene-co-divinylbenzene) samples, show that α_t, the residual number of sorbed molecules per phenyl group at a given level of desorption, is a linear function of α_s, the number of adsorbed molecules per accessible phenyl group in the polymer at thermodynamic equilibrium with excess test-liquid. Such linear relationships were noted at successive break-points in the kinetics of desorption (from gel-saturation to virtual dryness) that signaled sequentially (a) incipient elimination of adsorbed molecules from polymer in the rubbery state, (b) incipient transition from the rubbery state to the glassy state, (c) completion of this transition, and (d) successive depletions of five of the six populations of residual adsorbed molecules that were trapped in six different molecular environments by rigidification of the system during the transition. These results support the viewpoint that α_s is a parameter that reflects how well the molecular structure of the sorbed molecule can be accommodated by that of the monomer unit of the polymer.