Aromatic poly(pyridinium salt)s Part 2. Synthesis and properties of organo-soluble, rigid-rod poly(pyridinium triflate)s

A bis[pyrylium tetrafluoromethanesulfonate (triflate)], i.e. p-bis[4-(2,6-d iphenylpyrylium)]benzene ditriflate) (3), has been prepared and polymerized with a series of aromatic diamines. The polymerizations, which were carrie d out in a dimethylsulfoxide (DMSO)/toluene mixture at 150 degrees C for 3- 4 h, Even significantly faster than previous polymerizations of an analogou s bis(pyrylium tetrafluoroborate). The poly(pyridinium triflate)s (5) obtai ned were soluble in polar aprotic solvents and had inherent viscosities tha t ranged from 8.3 to 18.7 dl/g (0.1 g/dl in DMSO at 30.0 +/- 0.1 degrees C) . The rigid-rod polymers obtained from all-para-catenated diamines had visc osities comparable to those of other rigid-rod polyheterocyclics. All of th e polymers could be solution cast into tough thin films that had moduli of 2.3-5.5 GPa. The poly(pyridinium triflate)s (5) were significantly more the rmally and thermooxidatively stable than analogous poly(pyridinium tetraflu oroborate)s. The polymers underwent 5% weight losses near 451 degrees C in nitrogen and near 461 degrees C in air when subjected to thermal gravimetri c analysis at a heating rate of 10 degrees C/min. The differences in the po ly(pyridinium salt) stabilities were shown to be due to the differences in the stabilities of the counter ions. (C) 2000 Elsevier Science Ltd. All rig hts reserved.