Synthesis and Characterization of a Novel Low‐Viscosity Unsaturated Hyperbranched Polyester Resin

Abstract Hyperbranched thermosetting resin is the best additive for toughening and reinforcing linear thermosetting resin. A novel low‐viscosity unsaturated hyperbranched polyester resin (UHPR) is synthesized by the reaction between maleic anhydride monoisooctyl alcohol ester and a hydroxyl‐ended hyperbranched polyester resin (HPR) prepared from phthalic anhydride (PA) and trimethylolpropane (TMP). The structure of HPR is characterized by FT‐IR and 1 H NMR, and its degree of branching is deduced by comparing with the 1 H NMR spectrum of a model compound. The molecular weights of HPR and UHPR are determined by theoretical calculation and MALDI‐TOF MS measurements. This low‐viscosity (< 10 000 cP) novel UHPR can be applied in the field of environment‐friendly coatings and in toughening and reinforcing linear unsaturated polymers.