Investigation of the nematic-isotropic transition of a liquid crystalline polymer and determination of molecular diffusion coefficients using gas chromatography

Inverse gas chromatography has been used to study the nematic-isotropic tra nsition of a side chain liquid crystalline polymer (LCP). The mesogenic sid e groups are laterally attached to a polysiloxane backbone through a flexib le spacer. The nematic-isotropic transition of this LCP coated onto a glass capillary column is detected by considering the variation with temperature of the retention volume and of the theoretical plate number for the severa l probes. The molecular diffusion coefficients, D, of naphthalene, fluorene , pyrene and o-terphenyl have been determined at different temperatures in the nematic phase of the LCP as well as in the isotropic melt. The values r anged between 10(-14) and 10(-12) m(2) s(-1) for the polynuclear aromatic h ydrocarbon probes tested. (C) 2000 Elsevier Science B.V. All rights reserve d.