Study of conformation and dynamic of surfactant molecules in graphite oxide via NMR

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2016-08, Vol.122 (8), p.1-7, Article 760
• Main Authors: Ai, X. Q., Ma, L. G.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Condensed Matter Physics; Dynamic tests; Graphite; Machines; Manufacturing; Monolayers; Nanotechnology; Nuclear magnetic resonance; Optical and Electronic Materials; Orientation; Oxides; Physics; Physics and Astronomy; Processes; Segments; Surfaces and Interfaces; Surfactants; Thin Films
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-016-0299-x

The conformation and dynamic of surfactant in graphite oxide (GO) was investigated by solid-state 13 C magic-angle-spinning NMR and 1 H– 13 C cross-polarization/magic-angle-spinning NMR spectra. The conformation ordering of the alkyl chains in the confined system shows strong dependence on its orientation. While the alkyl chains parallel to the GO layer in lateral monolayer arrangement are in gauche conformation in addition to a small amount of all-trans conformation, those with orientation radiating away from the GO in paraffin bilayer arrangement is in all-trans conformation in addition to some gauche conformation even though high-order diffraction peaks appears. NMR results suggest that the least mobile segment is located at the GO-surfactant interface corresponding to the N-methylene group. Further from it, the mobility of the alkyl chain increases. The terminal methyl and N-methyl carbon groups have the highest mobile. The chains in all-trans conformational state are characterized as more rigid than chains with gauche conformation; each segment of the confined alkyl chains with the lateral monolayer arrangement exhibits less mobility as compared to that with the paraffin bilayer arrangement.