ON THE DYNAMICS OF MOBILIZATION IN SWELLING-DISSOLVING POLYMERIC SYSTEMS

The dynamics of the swelling-dissolution process in a rubbery polymer has been probed at a microscopic level for the first time by doing in situ NMR measurements. Some preliminary experiments on swelling-dissol ution of polyisoprene have been performed. The appearance of an interm ediate plateau in the mobility vs time plot in this system is highly s uggestive of ''pseudoequilibrium'' swelling, which persists for a surp risingly long time before any substantial dissolution can take place. Based on these microscopic observations, a mathematical model for the swelling-dissolution process has been developed which treats the swell ing process and the dissolution process as distinct decoupled processe s. ''Disengagement'' of polymer chains at the interface due to the hyd rodynamic forces on the polymer chains dangling into the liquid has be en postulated to be responsible for the increased dissolution rates un der shearing conditions. The simple model developed is able to correct ly predict the existence of the plateau under stagnant conditions as w ell as the disappearance of the plateau in a hydrodynamic field.