Aging and history effects in solvent-induced glass transition of polymer films

Aging and history in glassy polymer films are investigated in the frame of solvent-induced glass transition. By decreasing the pressure of a solvent vapour surrounding a polymer film, the film goes from the rubbery swollen state to the glassy dry state. Gravimetry experiments in a pressure-controlled chamber were performed to analyse aging behaviour for different kinds of solvent vapour pressure cycles. Results are utterly different from those obtained with equivalent temperature cycles: no marked memory effect can be shown; very important hysteresis at small activity as well as complex behaviour of the melting time according to the quench amplitude have been observed. This behaviour may be related to the coupled evolution of two variables, the free volume and the solvent fraction.