Structural and dynamic study of chemically modified polyHIPE by solid-state C-13 NMR spectroscopy

The structure of laboratory-made polyHIPEs was successfully characterized b y cross-polarity/magic-angle spinning, solid-state C-13 NMR experiments. Th e signals of vinyl groups appeared in the spectrum of the polyHIPE precurso r PH-CH=CH2, which was prepared by the polymerization of the divinylbenzene continuous phase from a highly concentrated reverse emulsion. This materia l was chem ically modified by the regioselective free-radical addition of t hiols to the pendant vinyl groups. Spectra of materials modified by the gra fting of C-8 and C-12 alkyl chains, PH-SC8 and PH-SC12, respectively, were produced. The signals of the vinyl groups disappeared in favor of methylene groups. This experiment clearly established that the alkyl chains were cov alently bound to the polymer. To elucidate the dynamic aspect of long chain s in polyHIPE, we measured the 13C spin-lattice relaxation times (T-1) of P H-SC12 from 25 to 100 degreesC with variable-temperature, solid-state, high -resolution C-13 NMR spectroscopy. revealing a strong variation in T-1 alon g the alkyl side chain. Furthermore, the crystallinity of a wide range of c hemically modified polyHIPEs, including PH-SC12, was studied with pulse H-1 NMR. (C) 2001 John Wiley & Sons, Inc.