LIQUID-CRYSTALLINE MAIN-CHAIN POLYMERS WITH A POLY(P-PHENYLENE TEREPHTHALATE) BACKBONE .1. SYNTHESIS, CHARACTERIZATION AND RHEOLOGY OF POLYESTERS WITH ALKOXY SIDE-CHAINS

The influence of the position and length of alkoxy substitutents on th e phase behaviour of poly(p-phenylene terephthalate)s was investigated by differential scanning calorimetry and rheological measurements. Th e two polymers with respectively dodecyloxy and hexyloxy side chains o n the terephthalate moiety (PTA12HQ and PTA6HQ) both showed stable liq uid-crystalline phases. For these two polymers the location of the tra nsition temperatures as a function of the molecular weight (inherent v iscosity) was shown to level off above an inherent viscosity of 2 dl g -1. From rheological measurements it is concluded that the layered mes ophase, shown by PTA6HQ and PTA12HQ, behaves more like a solid than a liquid. For the nematic mesophase, only shown by PTA6HQ, a minimum in the viscosity-temperature curve was found. The polymer with dodecyloxy substituents on the hydroquinone moiety (PTAHQ12) only shows mesomorp hic behaviour on cooling, while the polymer with double the amount of substituents (PTA12HQ12) does not show any liquid-crystalline behaviou r.