NMR analysis of interaction between styrene-divinylbenzene gel beads and small molecules

The interaction of small molecules such as cyclohexane, tetrahydrofuran, and acetonitrile with styrene-divinylbenzene copolymer gel beads were investigated by ¹³C-NMR spectroscopy. When the gel content was 0.1–0.3 g/mL, the ¹³C-NMR spectrum of the solvent displayed two peaks. A sharp peak at lower magnetic field was assigned to the free solvent, and a broad one to the solvent affected by the gel. This signal splitting is attributed to the upfield shift caused by aromatic rings of styrene units in the polymer chain. The nitrile carbon of acetonitrile showed the largest upfield shift. The mobility of small molecules in gel beads was also investigated using the nuclear magnetic relaxation method. In the case of good solvents for gel beads, the mobility was affected by the cross-linking density, whereas poor solvents exhibited little dependence of the cross-linking density. © 1995 John Wiley & Sons, Inc.