How to explain low molar masses in PolyHydroxyUrethanes (PHUs)

Abstract

PolyHydroxyUrethanes (PHUs) are desired to replace PolyUrethanes (PUs) which are synthesized using harmful isocyanates. However the synthesis of PHUs starting from bis(cyclic carbonate)s and polyamines usually leads to polymers with low molar masses. There are two model reactions carried out at 80°C. The first model used glycerol carbonate and n-hexylamine. The second model used carbonated benzylglycidyl ether and n-hexylamine. The findings demonstrated that the side reactions take place during the cyclic carbonate ring opening reaction by amines. 13C NMR and HRMS analyses demonstrated the formation of ureas as well as oxazolidinones and dehydration products that are seriously suspected to be responsible for the incapacity of reaching high molar masses during PHUs syntheses. Then a polymer from 1,10-decanediamine and an aliphatic polyether bis-carbonate was also synthesized at 80°C in DMF. The polyaddition was first analyzed by size exclusion chromatography until stabilization of the molar mass (Mn=10,300gmol−1, D=2.2). The effect of the addition of various amines and alcohols on the PHU polymer was evaluated based upon their physico-chemical properties. This preliminary study proves the formation of numerous side products such as ureas and oxazolidinones. These findings could explain the incapacity of PHUs to reach high molar masses when synthesized from difunctional precursors.