SOLID-STATE C-13-NMR ANALYSIS OF HYPERCROSSLINKED POLYSTYRENE

Hypercrosslinked polystyrenes, synthesized by reaction of linear or li ghtly crosslinked polystyrene with chloromethyl methyl ether(CME) and a Lewis acid in a good solvent, swell even in nonsolvents for polystyr ene. Structures and dynamics of hypercrosslinked polystyrenes in both dry solid and solvent-swollen gel states have been determined by C-13- NMR spectroscopy. Deconvolution of C-13 solid-state CP/MAS spectra gav e the relative numbers of quaternary carbon atoms in monosubstituted a nd disubstituted benzenes. A typical sample, crosslinked by reaction o f a mixture containing 0.5 mol of CME per mol of repeat units, contain s 35% of unreacted and 65% of crosslinked aromatic rings, and no resid ual chloromethyl groups. Gels swollen in CDCl3 and in CH3OH have resid ual static dipolar interactions enabling crosspolarization and require magic angle spinning (MAS) and high power H-1 decoupling to reduce ch emical shift anisotropy from similar to 10(4) Hz to similar to 10(3) H z. A single proton spin-lattice relaxation time in the rotating frame measured from all peaks in the C-13 spectra of dry samples indicates h omogeneity on a nanometer scale. Proton NMR line widths indicate no su bstantial molecular motions in a dry hypercrosslinked polystyrene up t o at least 200 degrees C. (C) 1997 John Wiley & Sons, Inc.