High-performance segmented polyurea by transesterification of diphenyl carbonates with aliphatic diamines

Abstract

In an effort to develop a green process for the production of elastomeric polyurethane–urea (PUaE) through a nonisocyanate route, a highly practical method was found using diphenyl carbonate (DPC) instead of diisocyanate as the carbonylation agent. The transesterification of aliphatic diamines in a solvent such as tetramethylene sulfone (TMS) with DPC results in a new process obtaining new segmented PUaE with high molecular weights and excellent mechanical performance. The key to the present success lies in the timing and sequence of the diamine addition forming initial carbamate intermediates in situ and then in shifting the equilibrium toward polyurea product formation by phenol removal from the TMS solution so that high‐molecular‐weight polyurea could be formed favorably. The most optimized polyurea films made in this study has a ηinh of 0.64, with high‐performance characteristics showing tensile strength of greater than 30 MPa and elongation exceeding 400% with decomposition temperature (5%) of >280 °C. Well‐defined soft‐ and hard‐segment domains were observed for the products as determined by atomic force microscope. This new improved process to produce segmented polyurea thereby complies fully with the principles of green chemistry using readily available chemicals. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2781–2790

Solvent-free processes to polyurea elastomers from diamines and diphenyl carbonate

“…8, the carbonyl absorption changed rapidly from carbonate (1780 cm −1 ) [19] to carbamate (1737 cm −1 ) [19] for the reaction mixture in the initial stage of the reaction, which was eventually consumed in two hours to form an urea product evidenced by its final absorption at 1640 cm −1 [19]. Therefore, these IR spectral changes indicate that the one-step meltpolymerization went through nearly identical changes to those done previously in TMS solution [6]. As indicated in Table 2, polyureas prepared in an one-step manner exhibit rather poor molecular weights as shown by its low inherent viscosity (η inh =0.29).…”

“…Because of its poor solubility, NS-P3 and NS-P4 could not be processed into films for further physical characterizations. Based on the previous TMS solution process [6], the threestep addition method has been shown to be the most desirable process of making segmented polyurea among other alternatives. Hence, we repeated a similar three-step sequential process except that TMS was eliminated.…”

“…In our recent NIR development [6] based on diphenyl carbonates (DPC), one of the most difficult problems encountered has been the environmental issue related to the solvent usage and recycling. Our prior processes rely heavily upon polar boiling solvents such as DMSO or TMS to facilitate the polymerization processes and to achieve high molecular weight products under relatively mild conditions.…”

Isocyanate‐ and Solvent‐Free Route to Thermoplastic Poly(amide‐urea) Derived from Renewable Resources

“…Thereby, it is of crucial importance that the polymerization temperature is higher with respect to the polyurea's melting temperature. In another nonisocyanate route (pathway G in Figure ) various groups prepared polyurea from biscarbamates by means of transurethane reactions . For example, semicrystalline and tough polyurea thermoplastics were obtained from melt‐phase transurethane polycondensation of diethylene glycol bis(3‐aminopropyl) ether with bis(hydroxyethyl)hexanediurethane and bis(hydroxyethyl)isophoronediurethane at 170 °C under a reduced pressure .…”

Synthesis of azo carbonate monomers and biocompatibility study of poly(azo-carbonate-urethane)s

“…However, in terms of green chemistry, today syntheses of polyurethanes free of isocyanate (NIPUs) are highly desirable. 15 There has been considerable attention paid to polycarbonate urethanes (PCUs) for improvement of their mechanical, antihydrolyzation and anti-oxidation properties compared to the traditional polyurethanes. 16 PCUs have excellent toughness, exibility, durability, chemical-and bio-stability and are biocompatible with human tissues, therefore they have been used or tested in modern medical applications, 17 like implanted medical devices, heart valves, blood pumps, cardiovascular implants, in reconstructive surgery, tissue repair, etc.…”