Eco-friendly synthesis of phthalonitrile polymers
A novel, efficient methodology for the synthesis of phthalonitrile derivatives was investigated, using ionic liquid (IL) and microwave (MW) media as well as both simultaneously. Phthalonitrile monomers containing imide linkages were prepared from the reaction between aromatic dianhydrides, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BPTA), pyromellitic dianhydride (PMDA), 4,4'-(hexafluroisopropylidene) diphthalic anhydride (6FDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BTDA) and the end-capping agent 4-(3-aminophenoxy) phthalonitrile through the imidization reaction. The use of the IL 1-butyl-3-methyl imidazoliumchloride as a solvent significantly increased the rate and yield of the reaction. The use of MW irradiation and reaction parameters significantly shortened the reaction time while enhancing the purity. The polymerization of the prepared phthalonitrile monomers was carried out with 3 wt % of aromatic diamine and 4,4'-oxydianiline (ODA) curing agent under MW irradiation. It is shown that condensation was successfully carried out using the recyclable IL medium under MW irradiation.