Macromolecules, Vol.29, No.11, 3787-3792, 1996
Synthesis and Characterization of a Poly(Benzobisthiazole) with a Substituted Biphenyl Moiety in the Main-Chain
Poly(benzobisthiazole)s containing an ortho-tetrasubstituted biphenyl moiety were synthesized via the polymerization of 2,5-diamino-1,4-benzenedithiol dihydrochloride with 2,2’-dinitro-6,6’-dimethylbiphenyl-4,4’-dicarboxylic acid. Sulfolane was used as a cosolvent with poly(phosphoric acid) (PPA), owing to the insolubility of the ortho-tetrasubstituted biphenyl monomer in PPA. The intrinsic viscosities of the poly(benzobisthiazole)s in methanesulfonic acid at 30 degrees C were in the range of 0.5-2.3 dL/g. Copolymerizations of 2,5-diamino-1,4-benzenedithiol dihydrochloride with terephthalic acid and 2,2’-dinitro-6,6’-dimethylbiphenyl-4, 4’-dicarboxylic acid were carried out as well by varying the ratio of the two dicarboxylic acid monomers in the reaction mixture. Intrinsic viscosities of up to 9.93 dL/g were achieved for the copolymers. Thermal stability of the copolymers was evaluated by thermogravimetric analysis (TGA). The stability for the copolymers was found to decrease with increased amount of the substituted biphenyl structure in the polymer backbone.