Add time:08/24/2019         Source:sciencedirect.com

The self-diffusion of parabens (methylparaben, propylparaben) and tetramethylsilane in the binary solvents carbon tetrachloride – co-solvent (methanol‑d4, acetone‑d6) has been investigated by the pulsed gradient spin-echo nuclear magnetic resonance (PGSE NMR) method in the range of temperatures from 278 to 318 K. The self-diffusion coefficients of paraben and tetramethylsilane increase as the concentration of acetone‑d6 increases and have a minimum for paraben and an inflection point for tetramethylsilane when the methanol‑d4 concentration increases. Based on the Stokes-Einstein equation it is shown that the paraben hydrodynamic radius in the binary solvent acetone‑d6 – carbon tetrachloride is practically independent of the acetone‑d6 concentration and has a maximum in the binary solvent methanol‑d4 – carbon tetrachloride. This behavior in both cases is explained by the paraben self-association degree and the heteroassociation degree of paraben – co-solvent.

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