Polymer drying. VIII. Molecular interpretations of desorption from polystyrene–liquid systems

Abstract

AbstractThe results obtained in time studies that monitored evaporation from liquid‐saturated poly(styrene‐co‐divinylbenzene) to virtual dryness at temperatures ranging from 20 to 80°C confirm those reported earlier for multireplicated time studies at 23 ± 1°C; i.e., when the residual composition (αt, in sorbed molecules per phenyl group) attains the glassy state composition, the value of αt thereafter is given by a linear combination of no more than six exponential decay functions. The logarithms of the rate constants (ki) for decay of these populations at a given temperature decreased linearly with i, the population identification number in the order of decreasing decay rate. The Arrhenius activation energy (ΔEi) for increase in ki with temperature was characteristic of the sorbed species, but it was independent of i. The logarithms of the frequency factors (Ai) decreased linearly with i, the slope of which was numerically equal to that observed for the corresponding ki relationships, signifying that the stepwise decrease of the latter at a given temperature is attributable primarily to a corresponding incremental decrease in entropy. It is suggested that this reflects discrete changes in the molecular structure of polymeric inclusion complexes formed during the transition from the rubbery to the glassy state, as discussed in the text. © 1993 John Wiley & Sons, Inc.