Synthesis and characterization of new poly(bisbenzothiazole)s containing 4-tert-butylcyclohexylidene and alkene units

A new series of poly(bisbenzothiazole)s(PBTs III_{1, 2}) containing 4-tert-butylcyclohexylidene and alkene units were prepared from 1, 1-bis(4-amino-3-mercaptophenyl)-4-tert-butylcyclohexane dihydrochloride(BAMPBCH·2HCl) and alkene dicarboxylic acids by direct polycondensation. Their chemical structures were characterized by IR, ¹H NMR and elementary analysis. These polymers exhibited improved solubility due to the introduction of 4-tert-butylcyclohexene group into their structures. They also maintained good thermal stability. The decomposition temperatures at 10% mass loss of them were above 419°C. In comparison with poly[p-phenylene-6, 6'-(4-tert-butylcyclohexene)bisbenzothiazole](PBT), the UV absorption spectra of PBTs III_1,2 showed that the λ_max were red shifted. And compared with poly(p-phenylene benzobisthiazole)(PBZT), the λ_max were blue shifted. The bandgaps of PBTs III_1,2 were 2.56 and 2.53 eV, which widened the optical bandgap range of the benzothiazole polymers. The emission wavelengths of PBTs III_{1, 2} were red shifted in contrast to PBT. The bulky pendant group decreased the aggregation degree of polymer chains. The results of EPR studies showed the intrinsic paramagnetic defects in PBTs III_1,2.