A new biphenol-like monomer, 4, 4'-methylenebis [ 4-( 1, 4-phenylene)-phthalazin-1 (2H)-one ] was synthesized from phthalic anhydride and diphenylmethane in two steps. In the first step, Friedel-Crafts reaction was carried out in, 1, 2-dichloroethane between diphenylmethane and phthalic anhydride. The obtained product was used in the second step with hydrazine monohydrate added into its solution,. followed by recrystallization in acetic acid. The melting point showed by differential scanning calorimetry of the bis(phthalazinone) monomer was 338.1degreesC. The overall yield of the biphenol-like monomer was 60%. A new polyphthalazinone was prepared from 4; 4'-difluorodiphenylketone(DFK) and 4, 4'-methylenebis [ 4-( 1, 4-phenylene)-phthalazin-1 (2H)-one ] by solution polycondensation in N-methyl-2-pyrrolidone (NMP) with anhydrous K2CO3 as a catalyst. High molecular weight polymer was formed in 8 h. at 190degreesC. The polymer was refined by precipitation from its 15% NMP solution with methanol as the precipitating agent. The powder of the polymer was dried in a vacuum oven under 120degreesC for 48 h and then under 200degreesC for 4 h. The intrinsic viscosity of the polymer was 0.58 dL/g in NMP at 25degreesC. The polymer showed high glass transition temperature (T-g) at 258degreesC by DSC. The decomposition temperature for 5 % weight loss (T-d5) in nitrogen measured by thermogravimetric analysis occurred, at 431degreesC. The solubility of the polymer was, investigated at room temperature. The polymer was soluble in NMP, m-cresol and partially soluble in chloroform, and insoluble in N, N-dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO). The methylene group and bis(phthalazinone) structure in the backbone of the polymer contribute much to the good solubility, and the rigid structure of bis (phthalazinone) retains its good thermal properties.
