The dynamics of a side chain liquid crystal copolymer at two dierent compositions has been investigated in its smectic A and C phases. J1x0 and J22x0 spectral densities have been determined for aromatic deuterium nuclei in the side chains and their interpretation has been carried out by means of several available motional models. The dy- namic process mainly contributing to relaxation has been found to be the rotation of the phenyl ring about its para-axis, that is best described by a small step rotational diusion model, where the diusion constant has an Arrhenius tem- perature dependence and a Gaussian distribution of the activation energies is present, indicating a remarkable degree of dynamic heterogeneity of this system.
Phenyl ring dynamics in a liquid crystal polymer through H-2 NMR spectroscopy
GEPPI, MARCO;VERACINI, CARLO ALBERTO
2001-01-01
Abstract
The dynamics of a side chain liquid crystal copolymer at two dierent compositions has been investigated in its smectic A and C phases. J1x0 and J22x0 spectral densities have been determined for aromatic deuterium nuclei in the side chains and their interpretation has been carried out by means of several available motional models. The dy- namic process mainly contributing to relaxation has been found to be the rotation of the phenyl ring about its para-axis, that is best described by a small step rotational diusion model, where the diusion constant has an Arrhenius tem- perature dependence and a Gaussian distribution of the activation energies is present, indicating a remarkable degree of dynamic heterogeneity of this system.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.