Solid-state 13C-NMR analysis of hypercrosslinked polystyrene

✍ Scribed by Roychen Joseph; Warren T. Ford; Shanmin Zhang; M. P. Tsyurupa; A. V. Pastukhov; V. A. Davankov

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 167 KB
• Volume: 35
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(199703)35:4<695::aid-pola12>3.0.co;2-i

✦ Synopsis

Hypercrosslinked polystyrenes, synthesized by reaction of linear or lightly crosslinked polystyrene with chloromethyl methyl ether (CME) and a Lewis acid in a good solvent, swell even in nonsolvents for polystyrene. Structures and dynamics of hypercrosslinked polystyrenes in both dry solid and solvent-swollen gel states have been determined by 13 C-NMR spectroscopy. Deconvolution of 13 C solid-state CP/MAS spectra gave the relative numbers of quaternary carbon atoms in monosubstituted and disubstituted benzenes. A typical sample, crosslinked by reaction of a mixture containing 0.5 mol of CME per mol of repeat units, contains 35% of unreacted and 65% of crosslinked aromatic rings, and no residual chloromethyl groups. Gels swollen in CDCl 3 and in CH 3 OH have residual static dipolar interactions enabling crosspolarization and require magic angle spinning (MAS) and high power 1 H decoupling to reduce chemical shift anisotropy from Ç 10 4 Hz to Ç 10 3 Hz. A single proton spin-lattice relaxation time in the rotating frame measured from all peaks in the 13 C spectra of dry samples indicates homogeneity on a nanometer scale. Proton NMR line widths indicate no substantial molecular motions in a dry hypercrosslinked polystyrene up to at least 200ЊC.