EFFECT OF MOLECULAR-STRUCTURE ON MESOMORPHISM .16. NEMATIC-ISOTROPIC THERMODYNAMICS FOR OLIGOMER MODELS OF LIQUID-CRYSTALLINE POLYMERS

Thermodynamic measurements of DELTA H and DELTA S for the nematic-isotropic transition for a homologous series of Siamese Twin diester liquid crystals are reported. These diesters are structurally related as conceptual dimers in the monomer yields oligomer yields polymer sequence of liquid crystals with a 4,4 prime -disubstituted phenyl benzoate mesogenic moiety. Both DELTA H and DELTA S values show an odd:even alternation with carbon number intermediate in magnitude between those for the monomeric and the polymeric mesogens. It is concluded that the Twin diesters are good models for these oligomers in the monomer yields oligomer yields polymer progression.