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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 43: Nanoparticles and Composite Materials I

CPP 43.7: Vortrag

Donnerstag, 17. März 2011, 15:45–16:00, ZEU 222

Unique Splitting Behavior of the C-C Symmetric Stretching Mode as a Raman Signature of Conformational Order of Intercalated Alkyl Chains in Modified Clay Composites — •Patrice Donfack¹, Elena A. Sagitova1^1,2, Kirill A. Prokhorov², Kirill V. Vodopianov², Goulnara Yu. Nikolaeva², Viktor A. Gerasin³, Nadezhda D. Merekalova³, Arnulf Materny¹, Evgeny M. Antipov³, and Pavel P. Pashinin² — ¹Center of Functional Materials and Nanomolecular Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany — ²A.M. Prokhorov General Physics Institute of RAS, Moscow, Russia — ³A.V. Topchiev Institute of Petrochemical Synthesis of RAS, Moscow, Russia

A specific conformational insight into clay modified by alkylammonium salts is presented. It is associated with the splitting of the symmetric C-C stretching mode at ≈ 1128 cm⁻¹ into two bands at 1128 and 1139 cm⁻¹ in the Raman spectra of sodium montmorillonite clay modified by alkylammonium surfactants, such as cetyltrimethyl ammonium bromide. We demonstrate that this splitting appears if two trans-segments of nonequivalent lengths and terminal groups coexist for the chains of the alkylammonium ions embedded into the clay interlayer space. Interestingly, this correlates with the conformational reorganization of alkylammonium molecules confined within clay galleries, as a function of the modifier content. Moreover, we show that the integral intensity ratio, I_(CH2)/I₍₇₀₅₎, allows a rapid and nondestructive quantification of the content of alkylammonium ions in the modified clays.