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

摘要

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.