Study On Synthesis Of Poly (Phthalazinone Ether)s By Ullmann C-N And C-O Condensation Reactions

The Ullmann condensation is one of the most well established reactions for aryl-oxygen and aryl-nitrogen bond formation. The order of ease of halide replacement is I, Br > Cl>> F. This is the reverse of the order of the activated halide for nucleophilic displacement polycondensation reactions. The harsh reaction conditions, however, have forced chemists to develop milder reaction conditions. Many modified synthetic methods have been reported for the formation of these bonds. There are also several reports about polyarylether formation via Ullmann C-O condensation reaction of various biphenols with dibromides in the presence of copper or cuprous salt with ligands. To the best of our knowledge, no polymerization reaction via combined Ullmann C-O and C-N condensation reactions in a one-pot process has emerged. The similar reactivity of NH and OH groups in 4-(4-hydroxyphenyl)-1-(2H)-phthalazinone (DHPZ) in the nucleophilic displacement polycondensation reactions encouraged us to explore its new polymerization reaction in this area. Herein synthesis of poly(phthalazinone ether)s by Ullmann C-N and C-O condensation reactions was studied in detailed.A new class of high molecular weight poly(phthalazinone ether)s has been successfully synthesized via the Ullmann condensation reaction of DHPZ and unactivated 4, 4'-dibromodiphenyl ether catalyzed by cuprous chloride with quinoline as ligand (10 mol% of DHPZ) and potassium carbonate (1.14 times of DHPZ). The effect of the reaction temperature on polymer molecular weight has been studied. The result indicates that when the reaction temperature is above 190℃, poly(phthalazinone ether)s with 18400 number average molecular weight can be obtained. But a part of gel product (30 wt% of the whole product) in the system was found when the reaction temperature was above 200℃, maybe owing to trace of oxygen which can lead to C-C coupling under the catalyst of cuprous salt.Other poly(phthalazinone ether)s from the reaction of DHPZ and other five dibromides have been subsequently prepared by the above mentioned reaction condition. ~1H-NMR was used to characterize the structure of poly(phthalazinone ether)s. DSC was used to study the thermal properties of the polymers. The polymers obtained have T_gs of above 237℃and T_d-5% of more than 484℃in nitrogen. Most of them can be soluble in chloroform, DMAC and NMP, and can be cast into tough and flexible films.The Ullmann condensation reaction of DHPZ and 2, 5-dibromothiophene was also investigated. When the molar ratio of DHPZ and 2, 5-dibromothiophene is 2:1, the product mainly contains dimer and trimers detected by LC-MS . To investage the reactivity of 2, 5-dibromothiophene, 4,4'-dibromo-diphenyl ether was added as the comonomer in the reaction system of DHPZ and 2, 5-dibromothiophene. The result indicates that when the molar ratio of 4,4'-dibromo-diphenyl ether and 2,5-dibromothiphene is 3:1, the film cast from the product is fragile, and only oligomers are obtained when their molar ratio is 1:1, indicating that the reactivity of 2,5-dibromothiophene is not enough for this reaction system.e cast into tough and flexible films.