We have investigated the experimental terahertz phonon modes in a model oligothiophene, the alpha-quaterthiophene (LT phase), by using infrared and inelastic neutron scattering spectroscopy in the 10-50 cm(-1) (0.3-1.5 THz) domain. The ability of density functional theory to reproduce the terahertz infrared phonon modes is also reported. In agreement with the calculation, the experimental infrared spectrum at 10 K is dominated by two phonon modes centered at 32 and 46 cm-(1) respectively assigned to an antiphasis translation mode and a libration of rings. (C) 2007 Published by Elsevier B.V.

Fourier transform infrared (FTIR) spectroscopy has been used to probe the organization of the organic fragments in lamellar bridged silsesquioxanes with organic substructures based on alkylene chains of various lengths and urea groups [O1.5Si(CH2)3NHCONH(CH2)nNHCONH(CH2)3SiO1.5] (n = 6, 8-12). The structure and intermolecular interactions (hydrophobic and H-bonding) of these well-defined self-structured hybrid silicas are discussed in relation to their powder X-ray diffraction patterns. The degree of structural order is determined by the length and parity of the alkylene spacer. A concomitant enhancement in the degree of condensation of the inorganic component and a decrease in the strength of the hydrophobic interactions between the organic components are demonstrated. The strength and directionality of the H-bonding are directly correlated to the crystalllinity of the organic-inorganic hybrid materials.

Inelastic neutron scattering investigations of the orthorhombic (O), tetragonal (T), and rhomboliedral (R) pressure-polymerized phases of C-60 as well as the pressure-dimerized state give evidence for differences in the responses of low-energy excitations between these phases. These differences are assigned to changes in low-energy interball modes dynamics as a function of the structure of pressure-polyutmerized phases. Far-infrared transmittance measurements complete the information of the low-frequency vibrational dynamics of these phases. The temperature dependence of these low-frequency excitations reveals a strong anharmonicity and possible phase transitions.

X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) investigations have been performed to study the self-assembly properties of lamellar organic–inorganic bridged silsesquioxanes. The organic part consists of an alkylene chain (flexible spacer) between two urea groups. For this study, two samples with different chain length (six and twelve carbon atoms) were synthesized. It is pointed out that the self-assembly properties of the organic component are controlled both by the hydrophobic interactions between alkylene chains and by the hydrogen bonds between urea groups. Infrared results clearly show a direct correlation between the strength of the hydrogen-bond and the crystallinity of the organic–inorganic hybrid materials. Furthermore, the study of the asymmetric stretching CH2 correlated with XRD results indicate that the disorder along the alkylene chain decreases with longer chain length.