Studies on the Synthesis of di-hydroxy Terminated di-Carbamate via Aminolysis of Propylene Carbonate

Abstract

This study presents a work on the aminolysis of propylene carbonate (PC) and the influence of protic and aprotic solvents, a relatively scarce topic in the existing literature. In this work, di-hydroxy terminated di-carbamate/hydroxyurethanes (HUs) have been synthesized employing an environmentally benign approach, specifically, the aminolysis of PC with five distinct amines namely, 1,6-hexane diamine (HDA), isophorone diamine (IPDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA), utilized in stoichiometric molar ratios. The obtained HUs can be further utilized for the synthesis of non-isocyanate polyurethanes (NIPUs). The aminolysis of PC with HDA in the presence of a protic solvent (MeOH) resulted in a complete conversion without a catalyst. Notably, when compared to the utilization of an aprotic solvent (DMSO) with catalysts (TBAB, LiCl, LiF, DBTDL, and TEA), the exclusive use of the protic solvent (MeOH) demonstrated superior catalytic activity in the context of ring opening/aminolysis of PC. PC conversion was quantified through ¹H NMR spectra. In depth structural elucidation and molecular weight determination were achieved using ¹H NMR, ¹³C NMR, and GPC analyses. Additionally, DSC assessments were employed to characterize glass transition and melting point temperatures. The utilization of solvents improves the polymer conversion, facilitates the processability of the reaction mixture, and enhances the mobility of the monomers throughout the reaction. The synthesized di-hydroxy terminated di-carbamates exhibit significant potential for applications in wood and metal coatings, films, adhesives, and as curing agents for epoxies.