FTIR-ATR studies of the sorption and diffusion of acetone/water mixtures in poly(vinyl alcohol)

The diffusion kinetics of water and acetone into dried PVOH polymer films have been measured simultaneously using the FTIR-ATR technique. The data have been fitted to a pseudo-Fickian model, along with allowance for a 'lag' time which lengthens considerably when the water mole fraction is low. It has been found that a case II model is viable at short times when the polymer is 'glassy' (< T-g). However, as water enters the polymer (unzipping the chain-chain hydrogen bonding), conversion to a 'gel' is rapid and the crystallinity drops concurrently. A Fickian-like model then becomes viable at intermediate times. FFIR-ATR is an excellent technique with which to study sorption from solvent mixtures. In this case, for example, we have demonstrated that acetone does not enter a dry polymer film and that the micro-crystallinity of the PVOH retums at longer times. Neither of these two potentially important results could have been obtained using gravimetric methods. (c) 2006 Elsevier Ltd. All rights reserved.