DIFFUSIONAL TRANSPORT FROM STRUCTURALLY VARIANT HYDROGELS

Diffusional release of solutes polymer matrices undergoing structural changes has been analysed by incorporating the dependence of solute diffusivity on rime. The functional dependence of diffusivity with time has been experimentally verified and its utility and limitations are discussed. Criteria for predicting release characteristics have been arrived at based on two model parameters, K and beta. Here K represents the reciprocal of the time required for the structural change and beta is the ratio of the solute diffusivity prior to the onset and after the completion of the structural change. The criteria, which are independent of the mechanistic details of the structural change, have been validated by analysing solute release from polymeric matrices undergoing diverse structural changes. The approach should be useful in predicting the relase characteristics of solutes on the basis of the physicochemical characteristics of the polymer-solute systems. It should also help in tailoring the polymers to obtain the desired release kinetics.