Enhanced site isolation and reduced site mobility have been demonstrated in polystyrene networks having trityl functionality at the cross-links through steady-state fluorescence measurements of intraresin excimer formation by 4-(1-pyrenyl)butanol labels and through ESR nitroxide spin-label studies. Suspension copolymerization of R,R-bis(4-vinylphenyl)benzyl alcohol with styrene afforded beads having trityl groups at the cross-links (C‚Tr). Pendent-functionalized beads (P‚Tr), prepared by copolymerization of R,R-diphenyl-4-vinylbenzyl alcohol with styrene and divinylbenzene served as a reference. Comparison of (Ie/Im) as a function of polymer loading and solvent demonstrated that crosslink functionalization reduced site interactions, providing 30% higher effective dilution of labels. ESR of polymers labeled with 2,2,6,6-tetramethyl-4-oxopiperidin-1-oxyl oxime demonstrated C‚Tr are less mobile than P‚Tr. Possible origins of enhanced site-separation and reduced mobility are discussed and explored through various experiments.

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