Some NMR Results on a Linear Nematic Polyester in the Bulk and in Mixtures with a Low Molecular Mass Nematic

Abstract

Proton and deuterium NMR results from a study of a nematic polyester (poly (4,4′ -dioxy- 2,2′dimethy-lazoxybenzene dodecanedioyl)) in bulk and in mixtures with perdeuterated para-azoxy-anisole (PAAd14) are presented. Two compounds are considered : polymer DDA9-L with an average degree of polymerisation ∼9 and the partially deuterated model compound 9DDA9-S d20. Both compounds exhibit a nematic plus isotropic (N + I) biphase. In the nematic phase, the molecules are aligned along the director with the spacers in an extended conformation. Relative fractions of N and I components and order parameter S are estimated. For DDA9-L, undulations of S with temperature suggest that in the N + I biphase, the nematic component is enriched with the longest molecular species. In the mixtures, S of DDA9-L and of PAA are estimated. The values and temperature dependence of S and of the relative order of the spacers and mesogens in the polymers are studied as a function of composition.