| Abstract
| - The microscopic rotational dynamics of a main chain liquidcrystalline (LC) poly(ether) in its nematic phaseis studied in detail by nonlinear least squares analysis of ESR spectrain the slow motional regime. Thiscomplements results reported in an accompanying paper, which focuses onmacroscopic translational diffusionusing the DID-ESR (dynamic imaging of diffusion by ESR) technique.Far infrared 250 GHz ESR spectroscopyis used to determine the magnetic g and A tensorsof the 3-carboxy-PROXYL spin label attached to the LCpolymer. ESR spectra of the labeled polymers of varying molecularweights are analyzed to yield the rotationaldiffusion coefficients and orientational order parameters.Different cases of the degree of macroscopicalignment are observed in these samples and accounted for in thesimulations. For molecular weights lowerthan 11 000 (for both tracers and matrices), the rotational diffusioncoefficient R̄ is found to correlate withthe molecular weight of the polymer matrix and to be independent of themolecular weight of tracer, suggestingthe importance of free volume for end-chain motion.Macroscopically aligned samples, corresponding tolower molecular weight LC polymers, show an inverse correlation ofR̄ with order parameter, consistent withobservations previously reported for nonpolymeric LCs, which wereassociated with free volume effects.
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