Ion pairs in macroreticular polystyrene resins: 2. EPR study using cation spin-labels

An EPR study using commercially available macroreticular resins (XAD-2 and XAD-4) coated and labeled with cationic probes 4-[(N,N-dimethyl-n-nonyl)ammonio]-2,2,6,6-tetramethylpiperidin-1-oxyl bromide and 4-[(N,N-dimethyl-n-hexadecyl)ammonio]-2,2,6,6-tetramethylpiperidin-1-oxyl iodide is reported. The nitrogen hyperfine coupling constants along the z direction, A{sub z}, were determined at 77 K. Rotational relaxation times and anisotropy of rotation were obtained based on procedures developed in part 1. The data are consistent with a model in which the cations are {open_quotes}anchored{close_quotes} to the resin framework through their hydrocarbon chains and the anionic components occupy an outer region within the resin pores with water occupying the polar ionic regions around the ion pairs. 12 refs., 7 figs., 5 tabs.