Synthesis and characterization of conjugated polyazines and polyazomethines containing the thienylene moiety and flexible hydrocarbon side chains

Condensation reactions of mono- and didodecyl-substituted-2,5-diformylthiop hene with hydrazine, p-diaminobenzene, 2,7-diaminofluorene, and 1,5-diamino naphatalene give the corresponding polyazines (PAZs) and polyazomethines (P AMs), which have been characterized by thermal, structural, and optical ana lyses. The former polymers begin to decompose at 300 degrees C, while the l atter polymers are stable up to 360 degrees C. All disubstituted polymers a nd the regioregular monosubstituted polyazines show nematic character. Disu bstituted polymers display a larger conjugation with respect to monosubstit uted ones. This effect has been attributed to a different conformation of t hiophenic rings versus imino-linkages assumed by the polymeric backbone in the two classes of polyazines. Particular attention has been devoted to stu dy the reactivity of mono- and disubstituted dialdehydes toward condensatio n with nucleophiles displaying different steric hindrance or power. Specifi cally the study of the reaction onset allowed us to determine the condition s to obtain regioregular monosubstituted polymers even with hydrazine, whic h is the less hindered and the more powerful nucleophile used.