Biodegradable isocyanate-free polyurethane films via a noncatalytic route: facile modified polycaprolactone triol and biobased diamine as precursors

Abstract

A facile synthesis of isocyanate free polyurethanes (PU) was executed by the reaction of biodegradable cyclic carbonate and sustainable diamines generated via chemical modification. The biodegradable polyol polycaprolactone triol (PCL) was transformed into a new glycerol carbonate derivative, PCL-(COOGC)₃, and subjected to polyaddition with the diamines linalool diamine (LLDA), isosorbide diamine (ISODA) and hexamethylene diamine (HDA). Polyaddition of PCL-(COOGC)₃ with the above diamine precursors was conducted via a one-pot reaction under catalyst-free reaction conditions prior to film casting. The above precursors were characterized by Fourier-transform infrared (FTIR) and ¹H and ¹³C nuclear magnetic resonance spectroscopies, high-resolution mass spectrometry and electrospray ionization matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, whereas the PU films were studied by attenuated total reflectance-FTIR spectroscopy, solid state ¹³C NMR, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, X-ray diffractometry, differential scanning calorimetry and thermogravimetric analysis. High onset degradation temperature (T_d) values were observed for the PU films PU-1 (345.8 °C), PU-2 (309.6 °C) and PU-3 (344.6 °C), and further studies, including cross-link density, water contact angle, swelling behaviour and biodegradation (phosphate-buffered saline medium, pH = 7.2 at 45 °C) measurements, were conducted.