Binary Liquid Gels

Abstract

In a recent paper W.I. Goldburg, D.W. Pohl, M. Lanz and I reported the fabrication of several binary liquid gels, swollen gels whose solvent is a binary liquid mixture near its critical temperature [1]. One might expect novel features for such gels, since the presence of polymer strands spaced on average at something like the gel-pore size should inhibit hydrodynamic degrees of freedom in the liquid’s phase separation, and the polymer strands in turn should have a preference for one of the separated liquid phases. The minimum effect one might expect is a slowing down of the gravitationally-induced late stages of spinodal decomposition by the mechanical presence of the polymer network. Much more dramatic effects would be expected if the polymer plays a more active role, and forms a ternary thermodynamic system with the solvents. Our observation is that the polymer strands interact with the liquid mixture strongly enough to frustrate the phase separation and dramatically alter the light scattering properties of the system in the critical region; howeyer, the interaction is sufficiently weak that light scattering does not resemble that expected of a ternary system.

Supported by the U.S. D.O.E. under grant no DE-F602-84ER45131.