Synthesis and characterization of isocyanate-free polyureas

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 20; no. 1; pp. 243 - 249
• Main Authors: Dennis, Joseph M., Steinberg, Limor I., Pekkanen, Allison M., Maiz, Jon, Hegde, Maruti, Müller, Alejandro J., Long, Timothy E.
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2018
• Subjects: Ammonia; Biodegradation; Calorimetry; Copolymers; Crystallization; Diamines; Differential scanning calorimetry; Dynamic mechanical analysis; Dynamic stability; Environmental degradation; Green chemistry; Isocyanates; Magnetic resonance spectroscopy; Mechanical properties; Melt temperature; NMR spectroscopy; Polymers; Polyureas; Stability analysis; Thermal analysis; Thermal stability; Thermogravimetric analysis; Urea; Urease
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/C7GC02996A

Due to continued health and safety concerns surrounding isocyanates, alternative synthetic routes to obtain urea-containing polymers is gaining much attention. Melt polycondensation of urea with diamines achieved polyureas in the absence of catalyst or solvents. 1 H NMR spectroscopy and thermogravimetric analysis confirmed targeted compositions and thermal stability, respectively. Differential scanning calorimetry and dynamic mechanical analysis provided insight into the copolymers’ thermal and morphological behavior. A steady increase in the melting temperature across the range of compositions suggested co-crystallization of the different repeating units, in sharp contrast to non-hydrogen bonded copolymers. Furthermore, tunable melt temperatures and mechanical performance illustrated the versatility of these copolymers in high performance applications. Finally, initial biodegradation studies using a naturally occurring, soil enzyme (urease) demonstrated steady degradation over 4 weeks, releasing ammonia as a potential nitrogen source for agricultural applications.