Preparation of poly(alkylenebenzimidazole) by ruthenium complex catalyzed polycondensation of 3,3?-diaminobenzidine with ?,?-diols

Abstract

The reactions of 3,3′-diaminobenzidine with 1,12-dodecanediol in 1 : 1–1:3 molar ratios in the presence of RuCl2(PPh3)3 catalyst give poly(alkylenebenzimidazole), [(CH2)11O(CH2)11Im/(CH2)10Im]n (Im: 5,5′-dibenzimidazole-2,2′-diyl) (Ia-Id) in 71–92% yields. The relative ratio between the [(CH2)11O (CH2)11Im] unit (A) and the [- (CH2)10Im] unit (B) in the polymer chain varies depending on the ratio of the substrates used. The polymer Ia obtained from the 1 : 3 reaction contains these structural units in a 98 : 2 ratio. The polymers are soluble in polar solvents such as DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), and NMP (N-methyl-2-pyrrolidone) and have molecular weights Mn (Mw) of 4,200–4,800 (4,800–6,500) by GPC (polystyrene standard). The polymerization of the diol and 3,3′-diaminobenzidine in higher molar ratios leads to partial cross-linking of the resulting polymers Ie and If via condensation of imidazole NH group with CH2OH group. Similar reactions of 3,3′-diaminobenzidine with α,ω-diols, HO(CH2)mOH (m = 4–10), in a 1 : 3 molar ratio give the polymers containing [(CH2)m−1O(CH2) m−1Im] and [(CH2) m−2Im] units with partial cross-linked structures. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1383–1392, 1999