Abstract
The influence of the position and length of alkoxy substitutents on the phase behaviour of poly( p-phenylene terephthalate)s was investigated by differential scanning calorimetry and rheological measurements. The two polymers with respectively dodecyloxy and hexyloxy side chains on the terephthalate moiety (PTA12HQ and PTA6HQ) both showed stable liquid-crystalline phases. For these two polymers the location of the transition temperatures as a function of the molecular weight (inherent viscosity) was shown to level off above an inherent viscosity of 2 dl g −1. From rheological measurements it is concluded that the layered mesophase, 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 mesomorphic behaviour on cooling, while the polymer with double the amount of substituents (PTA12HQ12) does not show any liquid-crystalline behaviour.
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