A New Way to Synthesize Poly(Urethane-Imide)s Based on Nitroethyl Carbamate Intermediary

Abstract

Poly(urethane-imide)s were prepared using a new method based on Michael addition and elimination reactions of bis(nitroethyl)urethane oligomers (PUNO₂) with bismaleimides. The bis(nitroethyl)urethane oligomers were synthesized from poly(tetramethylene oxide) glycol of molecular weight 650, 1000, 1500 and 2000 (Terathane 650, 1000, 1500 and 2000), 1,6-hexamethylene diisocyanate (HMDI) or dibenzyl diisocyanate (DBDI), and 2-nitroethanol, in the molar ratio of 1:2:2, in solution. The poly(urethane-imide)s were characterized using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopies, thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), contact angle measurements, and mechanical analysis. The dynamic contact angles of the cast films of these polymers were influenced by the molecular weight of the poly(tetramethylene oxide) glycol and the hard segment of the polyurethanes. Static mechanical measurements showed greater strength at break and modulus for the obtained poly(urethane-imide)s (PUI), the modulus being even ten times higher than that of PUNO₂ when using aryl diisocyanate.

Keywords:

• Mechanical properties
• Nitroethyl carbamate
• Poly(urethane-imide)s
• Thermal properties

ACKNOWLEDGMENTS

This article is dedicated to the 65th anniversary of “Petru Poni” Institute of Macromolecular Chemistry of Romanian Academy, Iasi, Romania.

Notes

^a Calculated from the initial composition.

^b The numeric-average molecular weight.

^c The weight-average molecular weight.

^d Polydispersity index.

^a Temperature corresponding to 5, 10 and 20% weight loss, respectively.

^b Maximum decomposition temperature.

^c Char yield at 600°C.

^a Glass transition temperature of soft segment poly(urethane-imide)s.

^b Melting temperature of soft segment of poly(urethane-imide)s.

^c Heat of melting/crystallization process, respectively.

^d Crystallization temperature of soft segment of poly(urethane-imide)s.

^e Glass transition temperature of hard segment of poly(urethane-imide)s.

^a Advanced contact angle measured in water.

^b Advanced contact angle measured in ethylene glycol.

^c Molar free energy of hysteresis.

^e Calculated from the dispersive (γ ^d ) and polar (γ ^p ) components.

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