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Composites containing 4- n -octyl-4′-cyanobiphenyl (8CB) either confined to nanopores of molecular sieves with very large pores or coating silica nanoparticles of aerosil type at high silica-to-8CB ratios are investigated by IR spectroscopy. Band shape analysis was performed in wavenumber regions in which the peaks due to CN stretching, CH stretching and CH out-of-plane vibrations appear. Some of molecules confined to molecular sieves show spectroscopic features characteristic to a bulk-like 8CB matter located in the centre of the pores or in the inter-grain space. Other features of the IR spectra are due to 8CB molecules located in the surface layer, mostly forming hydrogen bonds between their CN groups and surface OH groups. Another part of the 8CB molecules in the surface layer may also interact by π electrons of the aromatic rings. Hydrogen bonding is less hindered for the molecules of the surface layers onto aerosil particles than inside pores of the molecular sieves. Comparison is also made with the case of composites based on molecular sieves with small pores.

Broadband dielectric spectroscopy (10 −2 –10 9 Hz) was employed to study in a rather large temperature interval the molecular dynamics of the composite systems containing a nematic liquid crystal (LC), 4- n -pentyl-4′-cyanobiphenyl, confined to NaY, a zeolite with faujasite structure. Thermal analysis was also performed in order to get information concerning the loading of the zeolite and the possible phase transitions. No phase transitions and no relaxation processes of the LC molecules inside the pores were observed. But remarkably, in the presence of these molecules the dielectric behavior of the faujasite host changes due to modifications appeared in the mobility of Na + ions.

The confinement of a nematic liquid crystal (LC), 4-octyl-4′-cyanobiphenyl, in the molecular sieves of AlMCM-41 and cloverite type is investigated by dielectric spectroscopy, thermal analysis and FTIR spectroscopy. We focus herein on the samples containing the LC not only in the pores and cavities, but also on the external surface of the molecular sieve grains. A bulk-like dynamical behaviour was found for these samples. An interaction of the LC molecules with the surface took place by coordination to Lewis sites and by hydrogen bonding with OH groups.

The molecular dynamics of the liquid crystals 8CB and 5CB confined to the mesopores of the molecular sieve Al-MCM-41 with pore diameter less than 2.5 nm was investigated by broadband dielectric spectroscopy. The phase transitions of the liquid crystal cannot be detected for the molecules confined to the pores. Moreover it has been found that even about 20 K below the melting temperature of the bulk material a relaxation process occurs for molecules confined to the mesoporous material which does not exist in the bulk liquid crystal state. The temperature dependence of the relaxation rate of that process obeys a Vogel-Fulcher-Tammann law.

The gallophosphate cloverite has been investigated because of its applicability to act as a host for larger molecules. 4-n-pentyl-4′-cyanobiphenyl (5CB) and 4-n-octyl-4′-cyanobiphenyl (8CB) liquid crystals were used as guest molecules. The results show that the adsorption of liquid crystals from the gas phase proceeds without destruction of the cloverite structure. The typical phase properties of the liquid crystals remain unchanged after adsorption on cloverite: however, they appear with lower intensity in the DSC curve. A new smectic phase seems to be formed inside the cloverite pore system. FTIR measurements show the interaction of 5CB with the Lewis and Bronsted acid sites of cloverite. Desorption of liquid crystals out of the pore system proceeds slowly under liberation of the POH groups of the lattice. In summary, the results show that the gallophosphate cloverite is a suitable host for large molecules.

Hemoglobin (Hb) interaction with Hg 2+ ions was investigated by means of laser photolysis and spectroscopic methods. The binding of the gaseous axial ligands to the 3rd and 4th molecules of a Hb tetramer, l 3 ′ and l 4 ′, were found to show more relaxed features than in the absence of Hg 2+ ions. A heme iron oxidation takes also place. The kinetic parameters of this interaction were compared with those of the systems HbCu 2+ and HbSn(IV).

A series of AlMCM-41 molecular sieves was prepared with constant composition (Si/Al = 14.7) and presumably same pore structure but different pore diameters (from 2.3 to 4.6 nm). The pore size distribution is narrow for each sample. The rotational fluctuations of water molecules confined inside the pores were investigated applying broadband dielectric spectroscopy (10(-2)-10(7) Hz) over a large temperature interval (213-333 K). A relaxation process, slower than that expected for bulk water, was observed which is assigned to water molecules forming a surface layer on the pore walls. The estimated relaxation time has an unusual non-monotonic temperature dependence, which is rationalized and modeled assuming two competing processes: rotational fluctuations of constrained water molecules and defect formation (Ryabov model). This paper focuses on the defects and notably the influence of the hydroxyl groups of the pore walls. The Ryabov model is fitted to the data and characteristic parameters are obtained. Their dependence on pore diameter is considered for the first time. The found results are compared with those obtained for other types of molecular sieves and related materials.

Summary Modification of ZSM-5 zeolites (Si/Al=25) by impregnation with Ga, In or Tl salts is obtained. The interaction of Py molecules with the modified samples was spectroscopically studied: the components of IR peaks were ascribed to different adsorption sites, among which there are the modifier ions. On this basis, the location of modifier ions inside the zeolitic framework is discussed. Ammonia adsorption and textural measurements as well as recent electrochemical titration data [1] also support the differences regarding the deposition of the three modifiers.