A REPTATION MODEL FOR POLYMER DISSOLUTION

A model for the dissolution of a simple linear polymer in a solvent is presented. When the pure polymer and solvent are brought into contact, the solvent penetrates the polymer, causing it to swell. This swelling induces a nonrandom distribution of orientations for the polymer chains. The contribution to the free energy and chemical potentials of polymer and solvent due to this nonrandom distribution of orientations is evaluated in closed form from reptation theory. When this contribution is sufficiently large compared with the ordinary mixing terms, the system undergoes a phase separation into a gel-like concentrated solution phase and a dilute solution phase. The presence of this gel-like phase can significantly slow the dissolution process. Simple model calculations are present to illustrate the expected behavior of solvent/ polymer systems for which the magnitude of the orientational contribution to the free energy is sufficiently large to support a phase boundary between concentrated and dilute solution regions. © 1990, American Chemical Society. All rights reserved.