ANALYSIS OF CONTROLLED-RELEASE IN DISORDERED STRUCTURES - A PERCOLATION MODEL

The analysis of controlled-release kinetics in disordered models (perc olation clusters) of polymer matrices is developed in detail. It is sh own that the ''anomalous diffusion'' experimentally found in the relea se kinetics from swollen gels, M(t)/M(infinity) similar to t(n), n > 1 /2, cannot possibly be related to hindered diffusive motion in disorde red media, i.e, is not a consequence of the disordered structure of th e matrix. A kinetic model is proposed to account for an exponent n gre ater than 1/2. This is based on a two-phase kinetics which takes into account both field effects (deriving from potential interaction betwee n solute and polymeric matrix) and entrapping effects due to geometric constraints.