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Polymer-Dispersed Liquid Crystal, PDLC, are composite materials formed by liquid crystal droplets embedded in a polymer matrix. They allow to simultaneously exploit the electro-optical properties of liquid crystals and the mechanical properties of polymers, giving rise to interesting electro-optical devices such as smart windows. In this work monomer/LC mixtures in different weight ratios were polymerised in the presence of an external magnetic field to obtain PDLCs, whose director was aligned along the field direction. The time behaviour of LC order parameter was followed by 2H-NMR and the final morphology of PDLCs was investigated by SEM. Then, the electro-optical properties of PDLCs prepared in the absence of any magnetic field were investigated and correlated to the order parameter measurements, confirming the strong correlation between large order parameters and optimal electro-optical properties. [ABSTRACT FROM AUTHOR]

The three-dimensional structure and conformational equilibrium of flexible bioactive molecules in solution are of considerable importance in clarifying their role in chemical and biological activity, since their action takes place in a liquid medium. The use of residual dipolar couplings (RDCs) recently emerged as a promising and effective method to address this kind of investigation. In this brief review, the conformational analysis of several flexible non-steroidal anti-inflammatory drugs, belonging to the class of salicylates and a-arylpropionic acids (profens), is described using the RDCs measured in weakly aligning poly-γ-benzyl-L-glutamate solutions. By combining these experimental parameters, extracted by using different mono- and bi-dimensional nuclear magnetic resonance experiments, with the theoretical additive potential-direct probability description approach, accurate descriptions of the probability distributions have been obtained for all the drug molecules selected. [ABSTRACT FROM AUTHOR]

A comparison is made between the information which can be derived on structure, conformation and orientational order of the molecules in a nematic liquid crystal 4-pentyl-4'-cyanobiphenyl (5CB) from the NMR spectra of the deuterium atoms at natural abundance (NAD NMR), and the two-dimensional proton-detected 13C local field experiment (PDLF). The nine residual quadrupolar splittings, Δν k , obtained experimentally have been compared with quadrupolar tensors and a geometry and conformational potentials calculated by the DFT method B3LYP/6-311G**. The PDLF experiment yielded 42 scaled 13C-1H residual dipolar couplings, kD CiHj . The scaling factor, k, is determined experimentally by comparing unscaled and scaled residual dipolar couplings in a sample of fluorobenzene dissolved in a nematic liquid crystalline solvent. The corrected residual dipolar couplings, D CiHj , are used to investigate the structure and rotational potentials about each bond in the molecule. [ABSTRACT FROM AUTHOR]

For spin systems with N[sup I] and N[sup S] interacting nuclei of magnetogyric ratio γ[sub I] and γ[sub S] respectively, it is possible to obtain multiple quantum spectra characterized by changes in the magnetic numbers mX by N[sup I], (N[sup I]—1)…, 0 with X = I, S. The use of such heteronuclear MQ spectra as an aid in the automatic analysis of NMR spectra of both rigid and flexible molecules dissolved in liquid crystalline phases, is discussed. It has been found that when I = [sup 1]H and S = [sup 19]F, the decoupling efficiency of the standard multipulse sequences, developed and optimized for heteronuclear decoupling in isotropic liquids, depends on the spin system and also on the overall orientation of the molecule when orienting mesophases are involved. These facts impose limitations on the applicability of a procedure which, when the decoupled heteronuclear MQ spectrum is obtained, significantly reduces the computing requirements of the automated spectral analysis. [ABSTRACT FROM AUTHOR]