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The effect of molecular weight on the structure and temperature behavior of a thermotropic main-chain liquid crystalline copolyester

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Abstract

The structure of a fully aromatic thermotropic liquid crystalline (LC) copolyester poly-[(phenyl-p-phenylene)-co-(terephthalate)-co-(p-hydroxybenzoate)] (PES) prepared from terephthalic acid, phenylhydroquinone, andp-hydroxybenzoic acid at a molar ratio of 45/45/10, respectively, was studied at ambient and elevated temperatures by means of x-ray diffraction and differential scanning calorimetry as a function of molecular weight. On heating of PES fibers with fixed ends an irreversible phase separation process takes place above the glass transition point and two different crystalline phases are formed. A model is proposed where the phases are assumed to contain the constituents of the statistical copolymer in different amounts. The relative volume fraction of the two crystalline modifications depends on the molecular weight of the investigated fibers. At higher temperatures the melting of the two crystalline phases and their transition to a LC nematic mesophase is observed.

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Correspondence to Dr. M. Stamm.

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Stamm, M., Fischer, E.W., Antipov, E.M. et al. The effect of molecular weight on the structure and temperature behavior of a thermotropic main-chain liquid crystalline copolyester. Colloid Polym Sci 273, 23–31 (1995). https://doi.org/10.1007/BF00655670

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Key words

  • Structure
  • phase transitions
  • x-ray scattering