Dynamic investigations of liquid crystalline elastomers and their constituents by ²H NMR spectroscopy.

Several side-chain liquid single crystalline elastomers (LSCEs) were investigated by means of ²H NMR spectroscopy focusing on the temperature dependence of the spectral line width and spectral shape, as well as the T-dependence of spin-lattice and spin-spin relaxation times (T₁ and T₂). All measurements were performed at the Larmor frequency of 76.753 MHz for ²H. The LSCEs were prepared in the form of monodomain films by using either ²H-labelled monomers (or co-monomers), ²H-labelled cross-linkers or ²H-labelled molecular probes free to diffuse in the LSCE matrix. In all cases, deuterons are on the phenyl moiety. The main features of the measured ²H NMR properties (static and dynamic ones) in these different cases were discussed and comparedwith those of low-molecular-weightmesogens (i.e. the same molecules used as monomers or co-monomers in the side-chain LSCEs) in the nematic and smectic A phases. Among all investigated LSCE samples, those ²H-labelled on the cross-linker sites present distinct properties either on the ²H NMR spectral line width and spectral shape in the paranematic and in the nematic phases, which can be interpreted in terms of director reorientational dynamics in the intermediate-slow motional regime, taking into account the inherent local director misalignment of LSCEs. [ABSTRACT FROM AUTHOR]