Phenomena Associated with Gel-Water Interfaces. Analyses and Alternatives to the Long-Range Ordered Water Hypothesis

Interfacial regions between certain gels and their surrounding solutions were observed by Pollack and co-workers to exhibit several unexpected phenomena: (1) long-range exclusion of charged microspheres out to typical distances of similar to 100-200 mu m from the gel surface; (2) significant electrostatic potentials extending over comparable distances; (3) a reduced intensity of upward spontaneous thermal IR emission over a region 300-500 mu m wide at or near the gel solution interface; and (4) a significantly lower proton T-2 and an apparently reduced H2O self-diffusion coefficient over a zone similar to 60 mu m wide at or near the gel solution interface in high resolution NMR imaging experiments. To account for such observations, they proposed that a region of long-range ordered water bearing a net negative charge, but lacking mobile charge carriers, extended similar to 100-200 mu m outward from the gel surface. In this paper, various problems associated with the ordered water hypothesis, including contradictions,. by experiments from, many other laboratories, are : briefly discussed, and testable alternative explanations for the observed phenomena are proposed. Exclusion zones are suggested to arise from chemotaxis of the microspheres in long-range diffusion gradients of OH- (or H+) theory Of which was developed and compared with the observations on non-ionic gels in a companion paper. The same theory together with the expected directions of ion transfers between gel and solution are now used to predict qualitatively the exclusion/attraction behavior of microspheres in the presence of ionic gels and ionomers. The electrostatic potentials are interpreted as long-range liquid-junction, potentials arising from the same long-range diffusion gradients of OH-(or H+) and salt the unstirred solutions of Pollack and co-workers. Alternative explanations in terms of plausible experimental artifacts are suggested for both the reduced intensity of IR thermal emission and the lower proton T-2 and apparent H2O, diffusion coefficient in the NMR imaging experiments.