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 338.1℃.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 K 2CO 3 as a catalyst.High molecular weight polymer was formed in 8 h at 190℃.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 120℃ for 48*!h and then under 200℃ for 4*!h.The intrinsic viscosity of the polymer was 0.58*!dL/g in NMP at 25℃.The polymer showed high glass transition temperature (T g) at 258℃ by DSC.The decomposition temperature for 5% weight loss (T d5) in nitrogen measured by thermogravimetric analysis occurred at 431℃.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.
A novel unsymmetrical dianhydride containing 4\|(4\|hydroxylphenyl)\|2,3\|phthalazin\|1\|one was synthesized in order to improve the solubility of aromatic polyimides according to the principle of designing new monomers.This article reported a series of polyimide random copolymers derived from 4,4′ diamino diphenyl sulfone (DAPS),4,4′ oxyl dianiline (ODA) and the new dianhydride\|2 (3,4 dicarboxyl phenyl) 4 (3′,4′ dicarboxyl phenyl oxyl) phenyl 2,3 phthalazine 1 one dianhydride (DAH4) by“one step”solution polycondensation in m cresol with catalystic amount of isoquinoline at 200℃.Some properties of the copolymers were investigated by DSC,TG and mechanical analysis.The result shows that the η inh of copolymers is between 0 64 to 0 71 dL/g in m cresol at 25℃,and the T g of the copolymers are higher than that of pure poliymides containing 4,4′ oxyl dianiline (polymer 5).The relationship between T g and mole percent of DAPS is not obvious.Degradation temperature for 5% weight loss ( T d5 ) of the copolymers occurs all above 470℃ in air.The mechanical properties of the copolymers are lower owing to introducing sulfone groups into polymer’s backbone.In sharp contrast,the copolymers have good solubility and can be easily soluble in 1,1,2,2 tetrachloroethane(TCE), N,N dimethylacetamide(DMAc), N methyl 2 pyrrolidinone (NMP), m cresol and pyridine.Furthermore,the copolymers have better solubility in dimethyl sulfoxide (DMSO) and chloroform than the polyimide derived from DAH4 and ODA.
