Effect of methyl groups on the thermal properties of polyesters from methyl substituted 1,4‐butanediols and 4,4′‐biphenyldicarboxylic acid

Albert J.B. Loman, Leen van der Does, Adriaan Bantjes, Ivan Vulić

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Abstract

Results are reported on the effect of lateral methyl groups on the thermal properties of a series of polyesters prepared from diethyl 4,4′‐biphenyldicarboxylate and various methyl substituted 1,4‐butanediols. The diols were 1,4‐butanediol; 2‐methyl‐1,4‐butanediol; 2,2‐dimethyl‐1,4‐butanediol; 2,3‐dimethyl‐1,4‐butanediol; 2,2,3‐trimethyl‐1,4‐butanediol; and 2,2,3,3‐tetramethyl‐1,4‐butanediol. Apart from the tetramethyl derivatve, the transition temperatures of the methyl substituted polyesters were lower with respect of the unsubstituted polyester. On the basis of polarized photomicrographs, a smectic A mesophase was found for the unsubstituted polyester, whereas a nematic mesophase was observed for the 2‐methyl substituted polyster. The 2,2‐dimethyl, 2,3‐dimethyl, and the 2,2,3‐trimethyl substituted polyesters showed no liquid crystalline behavior. The 2,2,3,3‐tetramethyl derivative displayed a birefringent melt phase although the DSC measurements were not unambiguous. A copolyester based on diethyl 4,4′‐biphenyldicarboxylate, 1,4‐butanediol, and 2,2,3,3‐tetramethyl‐1,4‐butanediol showed a broad nematic mesophase. Further evidence for the nematic mesophase of this copolyester and the 2‐methyl substituted polyester was provided by dynamic rheological experiments. Based on thermogravimetric analysis, it was concluded that the thermal stability was affected only when four methyl side groups were present in the spacer.
Original languageEnglish
Pages (from-to)493-504
JournalJournal of polymer science. Part A: Polymer chemistry
Volume33
Issue number3
DOIs
Publication statusPublished - Feb 1995

Keywords

  • METIS-107115
  • IR-71212
  • Characterization
  • Butanediol
  • Smectic
  • 4,4′‐biphenyldicarboxylic acid
  • Liquid crystalline polymer
  • Methyl substitution
  • Nematic
  • Polyester
  • Synthesis
  • Thermal properties
  • X-ray analysis

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