Fractionary couplings of spin probe to backbone and side group dynamics of a liquid crystal polymer

The cholestane spin probe dynamics in a nematic polymeric matrix after annealing at a temperature value slightly above the T-NI was investigated by ESR spectroscopy in a wide temperature interval. Careful lineshape analysis showed that a two delta-like distribution better represented the experimental spectra. The dependance on temperature of the population in the difference sites was evalulated and compared with the analogous one previously found for the same polymer/spin probe system that had been annealed at temperature well above the T-NI.([1]) The temperature dependance of the spinning correlation time of the spin probe rearranging in slow and fast sites led us to locate them in the backbone and side groups of the polymer. The cooperativity degree in dynamics was quantified. A signature in temperature scale at the onset of cooperativity in backbone dynamics was recorded.