Symmetric C-C stretching mode splitting versus CH2-chain conformation order in sodium montmorillonite modified by cetyltrimethylammonium bromide

Sagitova, E.A.; Donfack, P.; Prokhorov, K.A.; Nikolaeva, G.Y.; Gerasin, V.A.; Merekalova, N.D.; Materny, A.; Antipov, E.M.; Pashinin, P.P.

Авторы: Sagitova E.A., Donfack P., Prokhorov K.A., Nikolaeva G.Y., Gerasin V.A., Merekalova N.D., Materny A., Antipov E.M., Pashinin P.P.
Журнал: Journal of Physical Chemistry B
Том: 116
Номер: 1
Год издания: 2012
Издательство: American Chemical Society
Местоположение издательства: United States
Первая страница: 221
Последняя страница: 231
DOI: 10.1021/jp208036c
Аннотация: Exploiting Raman spectroscopy and computational modeling, for the first time, we report and explain an interesting phenomenon in clay modified by cetyltrimethylammonium bromide. A splitting of the CH(2)-chain's symmetric C-C stretching Raman mode found at ~1128 cm(-1) in cetyltrimethylammonium bromide into two bands at 1128 and 1139 cm(-1) in clay modified by cetyltrimethylammonium bromide is observed. We demonstrate that this splitting appears if two types of trans-segments with nonequivalent lengths and terminal groups coexist in the CH(2)-chain of the alkylammonium ion embedded into the clay interlayer space. We report Raman experimental evidence for a CH(2)-chain bending within the clay galleries, resulting in the symmetric C-C stretching band splitting, as was also suggested by computational modeling. Noteworthy, we postulate that this unique behavior based on CH(2)-chain bending provides a general understanding of conformation reorganization and switching within long CH(2)-chain molecules confined within modified clay interlayer galleries. For all modifier concentrations, we show that the intercalated cetyltrimethylammonium ions exist in a liquid-like state, consisting mainly of trans conformations (~86%) of two types in approximately equal proportions. Moreover, we demonstrate that the integral Raman intensity ratio I(1295)(CH(2))/I(705)(clay) provides a rapid nondestructive quantification of the relative content of alkylammonium ions in modified clays. These results demonstrate that a simple direct monitoring of specific modifier-dependent interlayer conformational states is possible, which is of great importance for a tunable fabrication of modified clays-based nanocomposites with desired properties.
Добавил в систему: Герасин Виктор Анатольевич

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Symmetric C-C stretching mode splitting versus CH2-chain conformation order in sodium montmorillonite modified by cetyltrimethylammonium bromideстатья

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