INVESTIGATIONS CONCERNING DISSOLUTION AND SWELLING OF POLYMETHACRYLONITRILE IN ORGANIC LIQUIDS

The interaction of various liquids with polymethacrylonitrile (PMCN) was investigated with respect to their ability of acting as solvent or soaking agent. The extent of interaction with the polymer solvents were classified on the basis of the following characteristics—Category A liquids: UA, the rate of dissolution, is determined by Vrept, the rate of reptation. A swollen surface layer is formed during dissolution of polymer films. VA increases with decreasing Mw, the weight average molecular weight. Category B liquids: VA is determined by Vsolv, the rate of solvation. A swollen surface layer is not formed during dissolution of polymer films. VA is independent of Mw. Category C liquids: They are incapable of dissolving but capable of soaking PMCN. Penetration of polymer films is characterized by features typical of CASE II sorption—a sharp step‐wise penetrant profile proceeding with constant velocity Vsorp. Dissolution and soaking tests with X‐ray irradiated PMCN films carried out in category B or C liquids, respectively, revealed the importance of morphological properties regarding the rate of dissolution and sorption, respectively. The observed increase in VA and Vsorp with increasing exposure dose was concluded to be due to the radiation‐induced increase in free volume rather than to the decrease in Mw. Copyright © 1990 John Wiley & Sons, Inc.