SYNTHESIS AND POLYMERIZATION OF 3,4-DIAMINOTHIOPHENE DERIVATIVES

Abstract

Repeated nucleophilic aromatic substitutions (SNAr) were used to synthesize new conjugated polymers. Polymer 3 was obtained from SNAr reactions of 2,5-dichloro-3,4-dinitrothiophene (DCDNT) and p-phenylenediamine as insoluble red-brown solid in 61.2% yield. Polymer 4 was also obtained from SNAr reactions of DCDNT and N,N’-di-sec-butyl-p-phenylenediamine as partially soluble black solid in 59.3% yield. The polymer 3 was then reduced by SnCl2 to obtain polymer 5 containing 3,4-diaminothiophene units in 65.4% yield. The polymer 4 was also reduced to obtain polymer 6 in 34.8% yield. To study the functionalization of the polymers through the diamino groups, the model reaction of the reduced 2,5-dibromo-3,4-dinitrothiophene (DBDNT) and benzaldehyde produced the imidazole derivative 1 in 34% yield. Similarly, reaction of the reduced DCDNT and salicylaldehyde gave the product 2 in 17% yield. With these successes on monomeric units, the polymer 7 was synthesized in 40.2% yield by consecutive reduction and condensation with benzaldehyde on polymer 4 precursor. These newly synthesized conjugated polymers exhibited the characteristic UV-Vis maximum wavelength absorptions (λmax) in the bathochromic range of 550-670 nm.