Para‐ordered polybenzimidazole

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Abstract
A series of novel AB monomers such as 2‐[p‐carboxyphenyl]‐5,6‐diaminobenzimidazole hydrochloride have been synthesized. In addition, a new aromatic monomer, 1,3‐diamino‐4,6‐bis(p‐toluenesulfonamido)benzene has been prepared in high purity and substituted for 1,2,4,5‐tetraaminobenzene in a polymerization with terephthalic acid. Homopolymerization of the AB monomers, and polycondensation of monomer with terephthalic acid in polyphosphoric acid, produced the rod‐like para‐oriented polymer, poly[1,7‐dihydrobenzo(1,2‐d: 4,5‐d)diimidazole‐2,6‐diyl‐1,4‐phenylene]. The yellow polymer was completely soluble in methanesulfonic acid (MSA) and PPA, exhibiting intrinsic viscosities as high as 5 dl/g in MSA, and a blue opalescence in solution. Polymerization at temperatures above 225°C caused crystallization and subsequent precipitation to occur. Polymer thus obtained was completely insoluble in MSA and possessed a high degree of crystallinity as demonstrated by x‐ray analysis.

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