Polymer studies self diffusion

We have studied self-diffusion in polymer-like networks self-diffusion of transient chains (long entangled micelles) and tracer diffusion in the solvent (silica gels). Our results illustrate the role of reversible chain breaking and the scale-dependence of diffusion in the solvent. 

We will present here experimental results dealing with self-diffusion in polymer-like systems. We have first investigated chain self-diffusion in semidilute solutions of long cylindrical micelles which can break and reform "living polymers". We have also studied self-diffusion of a tracer molecule inside porous silica gels. 

Brown, W Stilbs, P Lindstrom, T, Self-Diffusion of Small Molecules in Cellulose Gels using FT-Pulsed Field Gradient NMR, Journal of Applied Polymer Science 29, 823,1984. Brownstein, KR Tarr, CE, Importance of Classical Diffusion in NMR Studies of Water in Biological Cells, Physical Review A 19, 2446, 1979. 

In polymers, the field-gradient spin-echo methods of measuring self-diffusion have been useful in three more or less distinct areas, the diffusion of polymers in their own melt and in concentrated solutions, in dilute and semidilute solutions, and the diffusion of penetrants and diluents in polymer hosts. A fourth category, the diffusion of bulky or flexible molecules in polymer hosts, is useful for subject matter not closely associated with the first and third category. It should be noted that the work reviewed here represents only a small fraction of the diffusion studies in polymers, including those using other NMR methods. 

Diffusion of Water in poly[PFSA] Membranes To describe diffusion of water through the membrane in the presence of a water activity gradient, an appropriate interdiffusion coefficient must be determined. Experimental methods used to study diffusion of water in these polymers, such as radiotracer and pulsed gradient spin-echo NMR techniques, probe intrad-iffusion coefficients, often referred to as tracer or self-diffusion coefficients, determined in the absence of a chemical potential gradient. Intra- and interdiffusion coefficients are related for the case of diffusion of a small molecule in a polymeric matrix as follows [28] ... 

I. Carmesin and K. Kremer (1988) The bond fluctuation method - a new effective algorithm for the dynamics of polymers in all spatial dimensions. Macromolecules 21, pp. 2819-2823 H.-P. Deutsch and K. Binder (1991) Interdiffusion and self-diffusion in polymer mixtures - a monte-carlo study. J. Chem. Phys. 94, pp. 2294-2304... 

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