Microwave-Accelerated Preparation of Aromatic Polyamides Containing Phthalimide and S-Valine Pendent Groups in Ionic Liquids
Ionic liquids (IL)s represent an attractive and potentially very valuable group of new solvents, which have the benefit of low vapour pressure and therefore easier handling than many conventional solvents. These liquids, because of their unique properties, are attracting a lot of attention to replace volatile organic solvents, eco-friendly and green media. This work describes microwave assisted polyamidation reaction of 5- (2-phthalimidyl-3-methylbutanoylamino)isophthalic acid as a diacid monomer with various aromatic diamines such as 4,4'-diaminodiphenyl sulphone, 4,4'-diaminodiphenylether, 4,4'-diaminodiphenyl methane, benzidine, p-phenylenediamine, mphenylenediamine, 2,5-diaminotoluene and 1,5-naphthalene diamine in the presence of different imidazolium salts and triphenyl phosphite without adding extra compounds. This technique of polymerization is a very fast and green process for polymer synthesis. This polymerization method benefits the advantages of elimination of volatile and toxic solvents such as NMP, very short reaction time and direct polymerization, so there is no need of preparation of diacid chloride and therefore, saves time and energy in this procedure. This method gave polyamides (PAs) with inherent viscosities ranging from 0.32-0.66 dLg-1. The resulting wholly aromatic PAs with bulky pendent groups, each has polyisophthalimide backbone substituted with phthalimide and S-valine groups in ring position 5 of the diacid, and different aromatic diamines. These polymers have chiral
centre in the pendant groups and show optical activity. They were characterized by FTIR, 1H NMR, elemental analysis and specific rotation techniques. Introduction of bulky and flexible clusters in these polymers pendant group; make them soluble in most polar aprotic solvents. Thermogravimetric analysis showed that these PAs exhibit high thermal stability.