Ionic liquids as novel, green media for clean synthesis of soluble aromatic-aliphatic poly(amide-ester)s containing hydroxynaphthalene urazole moiety
Ionic liquids (IL)s are very attractive and environmentally acceptable solvents. They can be used as green media for a number of chemical processes. In this investigation, for the advancement of ecological safety and improvement of technological ability of this process, room temperature ionic liquids (RTIL)s and quaternary ammonium salt, tetrabutylammonium bromide (TBAB) have been used both as an environmentally benign solvent and catalyst for the polycondensation 4-(3-hydroxynaphthalene)-1,2,4-triazolidine-3,5-dione (3HNTD) with aliphatic diacid chlorides, eliminating the need for a volatile organic solvent (VOS) and additional catalyst. The reaction of monomer3HNTD with acetyl chloride was performed in N,N-dimethylacetamide solution at different molar ratios, and the resulting mono-, di-, and trisubstituted derivatives were obtained in high yields and were finally used as models for polymerization reactions. The effects of various reaction parameters, such as the nature of the ILs, the amount of ILs, the reaction temperature, and the reaction time, on the yields and inherent viscosities of the resulting poly(amide-ester)s (PAE)s were studied. Polycondensation reactions successfully proceeded in IL without any additional extra components, such as triethylamine or pyridine, which are used in similar reactions in organic solvents. Therefore, ILs can act both as solvent and catalyst. In addition to the solubility test, inherent viscosity as a measure of molecular weight was determined. PAEs were obtained in high yields with inherent viscosities ranging from 0.18 to 0.34 dl g−1. This method was also compared with conventional method for the synthesis of PAEs. Fluorimetric studies of the model compound as well as polymers were performed.