THE LIFE TIME OF A DISSOLVING POLYMERIC PARTICLE

The life time of a dissolving polymeric particle in a hydrodynamic fie ld is predicted by building up a model that includes the phenomenon of reptation of the macromolecules, disengagement of these molecules fro m the gel-liquid interface and also diffusion in the boundary layer su rrounding the gel-liquid interface. The model predictions have been ve rified through some preliminary experiments. A striking experimental o bservation is that below a critical particle size, the dissolution tim e does not depend on the particle dimension, a finding that is in shar p contrast to the dissolution of ordinary low molecular weight systems . The minimum time for dissolution in the particle size independent re gion is shown to satisfy the prediction emanating from scaling theorie s. The implications of the findings in engineering practice have been discussed.