The structure of laboratory-made polyHIPEs was successfully characterized by cross-polarity/magic-angle spinning, solid-state C-13 NMR experiments. The signals of vinyl groups appeared in the spectrum of the polyHIPE precursor PH-CH=CH2, which was prepared by the polymerization of the divinylbenzene continuous phase from a highly concentrated reverse emulsion. This material was chem ically modified by the regioselective free-radical addition of thiols to the pendant vinyl groups. Spectra of materials modified by the grafting 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 covalently bound to the polymer. To elucidate the dynamic aspect of long chains in polyHIPE, we measured the 13C spin-lattice relaxation times (T-1) of PH-SC12 from 25 to 100 degreesC with variable-temperature, solid-state, high-resolution C-13 NMR spectroscopy. revealing a strong variation in T-1 along the alkyl side chain. Furthermore, the crystallinity of a wide range of chemically modified polyHIPEs, including PH-SC12, was studied with pulse H-1 NMR.