Room temperature synthesis of non-isocyanate polyurethanes (NIPUs) using highly reactive N-substituted 8-membered cyclic carbonates†
There is a growing interest to develop green synthetic pathways towards industrially relevant polymers such as polyurethanes without the use of toxic and dangerous isocyanate monomers. The most promising route towards non-isocyanate polyurethanes (NIPUs) is the aminolysis of dicyclic carbonates derived from renewable resources. Although, cyclic carbonates of 5- and 6-members have been successfully proposed, aminolysis of these compounds requires the use of high temperatures to obtain high conversions and subsequently high molecular weight NIPUs. Indeed, these cyclic carbonates do not allow the achievement of high molecular weight NIPUs using low reactive diamines analogous to two of the most industrially relevant aliphatic diisocyanates. Herein, we report a (bis) N-substituted 8-membered cyclic carbonate that could be prepared from naturally abundant epoxides, diamines and dimethyl carbonate using sustainable chemical routes. This N-substituted 8 membered cyclic carbonate appeared to be much more reactive than the smaller 5- and 6-membered cyclic carbonates. Due to this increased reactivity, we obtained high molecular weight NIPUs using a variety of diamines, including industrially relevant hindered aliphatic diamines, such as 5-amino-1,3,3-trimethylcyclohexanemethylamine (IPDA) and 4,4′-methylenebis(cyclohexylamine). The synthesis of NIPUs was demonstrated at room temperature without the need for any additional catalyst. Altogether, this paper shows that (bis) N-substituted 8-membered cyclic carbonates are ideal starting materials for the synthesis of sustainable non-isocyanate polyurethanes (NIPUs).