Influence Of The Nanoporous Material Surface
INFLUENCE OF THE NANOPOROUS MATERIAL SURFACE
ON THE ALIGNMENT OF FILLER COMPOUNDS
T. Bezrodnaya, G. Puchkovskaya, S. Makarenko,
V. Mel’nik, K. Nelipovich
Institute of Physics of NAS of Ukraine
Prospekt Nauki 46, 03028, Kyiv, Ukraine
Nowadays nanocomposition systems of “guest-host” type are of great interest because of significant changes observed in properties of capsulated substances in comparison with their properties in the bulk and because of perspective applications of these systems. Many works have been carried out on the study of dynamics and phase transitions of liquid crystals incorporated to the inner space of different nanoporous materials before. The aim of the present one is to investigate by the spectroscopic methods the behavior of molecular crystals with different polarity such as nitrobenzene C6H5NO2 (NB), benzophenone CO(C6H5)2 (BP) and behenic acid CH3(CH2)20COOH (kC22) encapsulated in nanocomposition structures. Mesoporous alumosilicate molecular sieves of MCM-41 type with the average channel diameter of 40Å have been used as matrices. The parameters of spectral bands caused by vibrations of polar groups namely -NO2, -C=O, -COOH have significant changes in IR spectra of capsulated substances. This results from the interaction between the filler and matrix active centers of Al(Si)-OH type located on the channel internal surface.
NB-MCM-41 system. IR-spectra (400-4000 cm-1, T=300 K) of pure NB, MCM-41 nanoporous matrix and of this matrix filled with NB have been obtained. Their analysis showed that NB molecules have been capsulated into the inner space of molecular sieves forming hydrogen bonds of Al(Si)-OH…ON- type.
BP-MCM-41 system. It has been investigated by both IR-spectroscopy (600-5000 cm-1, T=300 K) and phosphorescence (16000-26000 cm-1, T=4.2-200 K). Results obtained by us showed that the possible mechanism of the interaction between BP molecules and surface active centers is hydrogen bonds of Al(Si)-OH…O=C
different modifications: crystal rhombic and monoclinic, and also glass-like amorphous. Results of our study demonstrated that encapsulated BP is in its amorphous state.
kC22-MCM-41 system. IR spectra (400-4000 cm-1, T=300 K) of this system have been studied. Their analysis allows to draw the conclusion that capsulated molecules of kC22 have the completely stretching trans-conformation of alkyl chains but possibly their C-form can transform into B or E ones. It has also been shown that a part of kC22 molecules dissociates. This process is clearly seen from the appearance of IR band (ν=1588 cm-1) of COO–group symmetric vibrations.
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