A novel and green method for polycondensation reaction of 4‐substituted phenylurazoles with different diisocyanates under solvent‐free conditions

Abstract

In this investigation, a new method for stepgrowth polymerization reactions of 4-phenylurazole (PHU) and 4-(4-methoxyphenyl)urazole (MPU) with various diisocyanates were developed under solvent-free conditions. The reaction of these monomers with hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), and tolulyene-2,4-diisocyanate (TDI) were performed in the presence or absence of dibutyltin dilaurate (DBTDL) as a catalyst. The results of polymerization revealed that DBTDL did not have considerable effect on the polymerization process. The resulting polyureas showed good yields and moderate inherent viscosities ranging of 0.17-0.30 dL/g in N,N-dimethylformamide (DMF) at 258C. They are soluble in most polar organic solvents. All of the above polymers were characterized by 1 H-NMR, FTIR spectroscopy, and thermogravimetric analysis (TGA). This method was compared with the polymerization reaction in N,N-dimethylacetamide as a solvent via solution polymerization. Under solvent-free 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 and environmentally friendly method.

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

“…To compare the microwave-assisted method with conventional heating, we also performed the polymerization reactions under conventional heating (method II) [35]. In this method, polymerization was carried out by heating the monomers via one-step high temperature which took very long time (12 h versus 5 min ) compared to method I.…”

“…This could pertain to the aromatic, rigid structure of diisocyanate for PU6AI in comparison with the aliphatic and flexible structure of others PUs. The thermal behaviors of these polymers (method I) were also compared with PUs synthesized by a conventional method (method II) [35] and the results indicated that PUs prepared by solid-state condition under microwave had higher thermal properties according to the higher inherent viscosities USING: RAPID SOLID-STATE MICROWAVE-ASSISTED TECHNIQUE 323 (table 5). The polymers, PU4AI, PU5AI and PU6AI showed 10% weight loss at 283, 279 and 308 2 C, respectively.…”