The synthesis and thermal, optical and electrical properties of novel aromatic–aliphatic five- and six-membered thermotropic polyimides

Abstract

Polymers have been prepared by the polycondensation of 4,4′-(butane-1,4-diylbis(oxy)) bis(butane-4,1-diyl) bis(4-aminobenzoate) and 5,10,15,20,25,30,35,40,45,50,55,60-dodecaoxatetrahexacontane-1,64-diyl bis(4-aminobenzoate) (PBBA 1200) with three dianhydrides based on naphthalene, perylene and phthalic moieties, respectively. This has resulted in five novel aliphatic–aromatic polyimides. The polyimides differed in aliphatic chain length and whether the imide ring was five- or six-membered. The chemical structure of the polyimides has been confirmed by ¹H NMR and FTIR spectroscopy and by elemental analysis. The optical and electrical properties of the polyimides have been studied using current–voltage measurements, and the effect of the polyimide structure on thermal and mesomorphic behaviour investigated by differential scanning calorimetry and polarising optical microscopy. Wide-angle X-ray diffraction at different temperatures was employed to confirm the structural properties of the polyimides. All the novel polyimides, with the sole exception of that obtained from PBBA1200 and 3,4,9,10-perylenetetracarboxylic dianhydride, showed liquid crystalline properties. As far as we are aware, this is the first time that six-membered polyimides exhibiting liquid crystalline properties have been reported.

Keywords:

• polyimide
• polynaphthimide
• perylene moieties
• thermotropic liquid crystals

Acknowledgements

The authors wish to thank Mr M. Domanski for his help in determining the I–V characteristics of the polyimides, and Dr W. Mielcarek for conducting the X-ray measurements. This research was partly carried out within the PAN/CNRS–DAE collaboration programme No. 22529.