POLYMER DRYING .10. A RECONSIDERATION OF THE KINETICS OF EVAPORATION FROM POLYMER LIQUID-SYSTEMS DURING THE INTERVAL OF TRANSITION FROM THERUBBERY TO A GLASSY STATE

This kinetic restudy of the physical changes that occur during evapora tion-induced transition from the rubbery to a glassy state of polystyr ene-liquid systems shows that such transitions occur via two mechanist ic pathways. The first is random nucleation of microdomains of self-as sociated polymer segments owing to a time-dependent logarithmic decrea se in the number of adsorbed volatile molecules per phenyl group of re sidual mobile polymer segments. The second is a thermodynamically driv en self-association of adjacent monomer units with concomitant expulsi on of the adsorbed molecules, which appears to propagate via a ''domin o-like'' chain reaction. Conceptually this is a three-dimensional ''zi ppering-up'' of suitably close polymer segments to produce the corresp onding macrostructural network of self-associated polymer. The kinetic s 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. (C) 1994 John Wiley & Sons, Inc.