Polymer drying. X. A recondsideration of the kinetics of evaporation from polymer-liquid systems during the interval of transition from the rubbery to a glassy state

This kinetic restudy of the physical changes that occur during evaporation‐induced transition from the rubbery to a glassy state of polystyrene–liquid systems shows that such transitions occur via two mechanistic pathways. The first is random nucleation of microdomains of self‐associated polymer segments owing to a time‐dependent logarithmic decrease in the number of adsorbed volatile molecules per phenyl group of residual mobile polymer segments. The second is a therodynamically driven self‐association of adjacent monomer units with concomitant explusion of the adsorbed molecules, which appears to propagate via a “dominolike” chain reaction. Conceptually this is a three‐dimensional “zippering‐up” of suitably close polymer segments to produce the corresponding macrostructural network of self‐associated polymer. The kinetics of the latter is zero‐order, and this dominates the overall kinetics of evaporation during the latter portion of the transition interval, presumably owing to changes in entropy of the system as it progresses from the mobility characteristic of the rubbery state to the rigidity characteristic of a glassy state. © 1994 John Wiley & Sons, Inc.