Epoxy-free synthesis of aromatic dicyclocarbonates and the related strong epoxy hybrid non-isocyanate polyurethanes

A new epoxy-free method for synthesizing aromatic five-membered cyclic carbonates (5CCs) was established, and several epoxy hybrid non-isocyanate polyurethanes (HNIPUs) with aromatic segments were prepared from them. First, two aromatic tetraols were synthesized from hydroquinone and bisphenol S with 3-chloro-1,2-propanediol in aqueous NaOH solution. Then, the aromatic 5CCs were prepared through a carbonylation reaction of the tetraols with diethyl carbonate in the presence of K2CO3. Six H2N- terminated polyhydroxyurethane prepolymers (PHUs) were prepared through bulk aminolysis polyaddition of the 5CCs with excessive hexamethylene diamine, and they were crosslinked with an aliphatic epoxy resin to obtain crosslinked HNIPUs. The HNIPUs were amorphous crosslinked hybrid PUs with high crosslinking extent. They showed excellent mechanical property with tensile strength up to 45.1 MPa and good toughness. Introducing aromatic segments increased the stiffness, glass transition temperature, intermolecular interactions, and mechanical properties, and also influenced the swelling properties of HNIPUs.