A procedure for the analysis of the electron spin resonance (ESR) lineshape of a cholestane paramagnetic tracer dissolved in a liquid crystalline polymer is described. Due to its rodlike geometry, the cholestane probe is subjected to an anisotropic reorientational motion in the polymer matrix. On the basis of the generalized Mori theory, simulation approaches to the lineshape have been developed. The ESR lineshape has been calculated for a molecule reorienting in a homogeneous molecular site according to diffusion or jump motion. Moreover, the case of inhomogeneous sites with continuous or discrete distribution functions was also accounted for. Systematic comparison with experimental spectra has been carried out, and a two-delta distribution function of the molecular sites has been singled out as best description of the experiment. The temperature dependence of the two species has been fully investigated and the spatial character of the heterogeneity has been proved.
On the simulation of inhomogeneous ESR lineshape of a spin probe in a liquid crystalline polymer
ANDREOZZI, LAURA;GIORDANO, MARCO;
2002-01-01
Abstract
A procedure for the analysis of the electron spin resonance (ESR) lineshape of a cholestane paramagnetic tracer dissolved in a liquid crystalline polymer is described. Due to its rodlike geometry, the cholestane probe is subjected to an anisotropic reorientational motion in the polymer matrix. On the basis of the generalized Mori theory, simulation approaches to the lineshape have been developed. The ESR lineshape has been calculated for a molecule reorienting in a homogeneous molecular site according to diffusion or jump motion. Moreover, the case of inhomogeneous sites with continuous or discrete distribution functions was also accounted for. Systematic comparison with experimental spectra has been carried out, and a two-delta distribution function of the molecular sites has been singled out as best description of the experiment. The temperature dependence of the two species has been fully investigated and the spatial character of the heterogeneity has been proved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
