Compared properties of related aromatic poly(1,3,4-oxadiazole-amide)s

Two series of aromatic poly(1,3,4-oxadiazole-amide)s have been synthesized by low-temperature solution poly-condensation reaction of equimolar amounts of aromatic diamines containing preformed oxadiazole rings with diacid chlorides having silicon or hexafluoroisopropylidene groups. These polymers are soluble in polar aprotic solvents and show high thermal stability with decomposition temperature being above 400 degreesC and glass transition temperature in the range of 250-350 degreesC. The polyoxadiazole-amides have weight- and number-average molecular weights in the range of 207000-330000 and 77000-131000, respectively. Conformational parameters of these polymers were calculated by Monte Carlo method with allowance for hindered rotation and discussed in relation with thermal properties. Polymer solutions in NMP were processed into thin free-standing films that showed good mechanical properties with tensile strength in the range of 50-100 MPa, tensile modulus in the range of 2.25-3.56 GPa and elongation to break in the range of 1.65-8.58%. (C) 2003 Elsevier Ltd. All rights reserved.