A Green Route for Synthesis of Different Polyureas Based on Phenylurazole: Rapid Solid-state, Microwave-assisted Technique

Abstract

Solid-state microwave synthesis was found to give a simple, rapid and economical route to prepare different kinds of materials. In this investigation, a new method for solid-state polymerization reaction of 4-phenylurazole (PHU ) and 4-(4-methoxyphenyl)urazole (MPU) with different diisocyanates was developed under microwave irradiation. The reaction of PHU and MPU with hexamethylene diisocyanate, isophorone diisocyanate, and tolulyene-2,4-diisocyanate were performed under solid-state conditions in the presence or absence of dibutyltin dilaurate as a catalyst. The resulting polyureas showed good yields and moderate inherent viscosities ranging of 0.20 to 0.34 dL g-1 in N,N-dimethylformamide at 30 °C. All of the aforementioned polymers were characterized by 1 H-NMR, FT-IR spectroscopy and thermogravimetric analysis. This method was compared with solid-state polymerization under high temperature conditions and also with the solution polymerization reaction in N,N-dimethylacetamide. Under microwave-assisted, solid-state conditions, higher yields and inherent viscosities were obtained. In addition in this method we do not need to use any solvents and the polymerization reaction can be classified as a green, cost-effective and environmentally friendly method.