Thermotropic Liquid Crystalline Poly(ester β-sulfide)s Based On Twin Hexamethylene-spaced p-oxybenzoyl Diads

A series of poly (ester β-sulfide) s, 6Sn, has been prepared by reacting the mesogenic hexamethylene bis [4-[[4-(acryloyloxy)benzoyl]oxy] benzoate] (1) with α,ω-alkanedithiols with a different number n of methylene units (n = 2–10). All of the polymers exhibit a nematic phase whose stability depends on the length of the dithiol segment. The nematic phases are enantiotropic with the only exception being that of the last term of the series, for which monotropic character has been detected. Onset and isotropization temperatures of the mesophase show a pronounced even–odd alternation that also holds for the isotropization entropy. A detailed study of the dependence of thermal properties upon the molecular weight is reported and indications are provided on their practical independence of the molecular weight at DP_n≥ 4–5.