Preparation of organo-soluble poly[(2,2′-m-phenylene)-5,5′-bibenzimidazole] with high yield by homogeneous nitration reaction
✍ Scribed by Won Seok Lyoo; Jin Hyun Choi; Sung Soo Han; Won Sik Yoon; Min Su Park; Byung Chul Ji; Junhan Cho
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 168 KB
- Volume
- 78
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
To prepare organo-soluble poly[(2,2,Ј-m-phenylene)-5,5Ј-bibenzimidazole] (PBI) with high yield, a homogeneous nitration of PBI was attempted. Nitro-substituted PBI (NO 2 -PBI) was synthesized through the homogeneous reaction of the PBI powder with nitric acid in sulfuric acid. The degree of substitution (DS) of this NO 2 -PBI is higher than that of the NO 2 -PBI prepared through the heterogeneous reaction of the PBI fiber. The viscosity of the NO 2 -PBI prepared through the homogeneous reaction decreased with increasing amount of nitric acid added. The DS of the NO 2 -PBI reached the maximum value of 2. The substitution efficiency of nitro groups decreased as the amount of nitric acid added increased. When a small quantity of nitric acid was added, the substitution of the sulfonic acid group was confirmed as well as that of the nitro group. The solubility of the NO 2 -PBI depended strongly on the DS. The NO 2 -PBI having the DS of about 2 was completely soluble in dimethylacetamide and almost soluble in N-methylpyrrolidone. At an elevated temperature, it was also soluble in other polar aprotic solvents such as dimethylformamide and dimethylsulfoxide.