Polymers PGSE studies

In his PGSE study of polyethylene oxide and polydimethylsiloxane in QHg and CHC13, Tanner 39) also measured the diffusion of a fixed fraction of solvent in the polymers. He concluded that their diffusion rate in polymers of molecular weight lower than their own was approximately equal to that of the polymers. As the polymer molecular weight exceeded that of the solvent, the solvent diffusion rate approached a constant value, independent of polymer molecular weight. Tanner offered semiempirical explanations for this effect. 

Strong evidence of ionic association was found by Stilbs and Lindman 69) in their PGSE study of aqueous polyelectrolyte solutions, polyacrylic acid and poly-methacrylic acid, neutralized by tetramethylammonium hydroxide, with or without sodium counterions. While polymer diffusion could not be detected since its T2 was too short, TMAOH and water diffusion was measured as function of degree of neutralization a, or Na+ content. A pronounced minimum of D(TMAOH) near a = 1 was interpreted in terms of a two-site model, leading to the determination that at a = 1, approximately half of the counterions are bound in both systems. Fourier transform techniques permitted the simultaneous measurement of diffusion of water and TMAOH. 

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