Transport of Small Molecules in Swollen Polymer Beads
Pulsed-field-gradient spin-echo (PGSE) NMR experiments have been used to determine self-diffusion coefficients of toluene in swollen cross-linked polystyrene beads with 5.7-40% cross-linking. Self-diffusion coefficients were also determined for toluene in linear polystyrene solutions over a concentration range of 0.1-0.7 weight fraction of polymer. The swelling ratios of the cross-linked beads were used to determine the concentration of toluene in the beads by assuming that the increase in volume is due only to solvent uptake. A comparison of solvent diffusion in the cross-linked and the non-cross-linked systems at similar concentrations shows remarkably close agreement. These results suggest that the diffusion rate in the cross-linked polymer beads is not significantly affected by the presence of cross-links and is mainly determined by the concentration of solvent in the bead.
S. Pickup et al., "Transport of Small Molecules in Swollen Polymer Beads," Journal of the American Chemical Society, vol. 108, no. 14, pp. 3987-3990, American Chemical Society (ACS), Jan 1986.
The definitive version is available at http://dx.doi.org/10.1021/ja00274a022
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