Copolymerization of Ethylene Carbonate and 1,2-Propylene Carbonate with Tetramethylene Urea and Characterization of the Polyurethanes

Tetramethylene urea (TeU, 1) is successfully copolymerized with 1,2‐propylene carbonate (PC, 2) leading to a polyurethane ($\overline M _{\rm n}$ = 12 200; $\overline M _{\rm w}$ 18 400; $\overline M _{\rm w} /\overline M _{\rm n}$ = 1.50) with a Tm of 145.7 °C and a Tg of 53.7 °C. Mechanistic studies with a blocked isocyanate model compound revealed that, at no stage of the reaction is the TeU ring opened to form an isocyanate. Hence, a well‐underlined mechanism for the copolymerization is proposed. Furthermore, TeU is successfully copolymerized with mixtures of PC and ethylene carbonate (EC, 3). From NMR spectroscopic data of the polyurethanes obtained, it is concluded that PC is less reactive than EC. However, it is possible to increase the PC content in poly(TeU‐EC‐stat‐TeU‐PC) by increasing the PC/EC ratio in the feed. 13C NMR spectroscopy reveals that a random copolymer is obtained. This conclusion is supported by differential scanning calorimetry (DSC) data, which show a continuous decrease in Tm with increasing PC content. Tm was found to decrease with increasing PC content.