SYNTHESIS AND CHARACTERIZATION OF POLY(1-BENZOYLTHIOSEMICARBAZIDE) AND POLY(1,3,4-THIADIAZOLE AMINE) FROM 2-(P-AMINOPHENYL)-1,3,4-OXADIAZOLINE-5-THIONE VIA RING-OPENING PROCESS

A novel thermally stable and semiconducting polyheterocycle, poly(1,3, 4-thiadiazole amine), was synthesized from 2-(p-aminophenyl)-1,3,4-oxa diazoline-5-thione via ring-opening. The polymer is a new class of ord ered alternating copoly(aniline) containing 1,3,4-thiadiazole heterocy clic units. An investigation of the reaction of 2-phenyl-1,3,4-oxadiaz oline-5-thione with aniline was conducted as a model reaction for the polymerization, and poly(phosphoric acid) (PPA) and phosphorus pentoxi de/methanesulfonic acid (PPMA) were found to be favorable both as cond ensing agent and solvent for the formation of 2-anilino-5-phenyl-1,3,4 -thiadiazole as a model compound. The polymerization was carried out b oth by two-step procedure that included ring-opening self-polyaddition giving poly(1-benzoylthiosemicarbazide), followed by cyclodehydration to poly(1,3,4-thiadiazole amine), and by a one-step procedure includi ng cyclodehydration in situ. The poly(1-benzoylthiosemicarbazide) whic h was formed in the first step in m-cresol had reduced viscosities up to 0,42 dL.g(-1), and it was converted to poly(1,3,4-thiadiazole amine ) by treating in PPA or PPMA. Poly(1,3,4-thiadiazole amine) having red uced viscosities up to 0,25 dL.g(-1) was also synthesized by the direc t one-step polymerization in PPA or PPMA. The polymer is highly therma lly stable and exhibited n1 weight loss up to 350 degrees C under nitr ogen. Its electric conductivity was less than 10(-10) S.cm(-1) at ambi ent temperature, but markedly increased to 2,9 10(-7) S.cm(-1) upon do ping with iodine.