Oleanolic\nAcid-Derived High-Glass-Transition-Temperature\nMethacrylic Polymers

Four new monomers based on the naturally occurring pentacyclic\ntriterpenoid oleanolic acid (OA) were synthesized by introducing a\nmethacrylate group at either the hydroxyl or carboxylic acid positions.\nAfter establishing their (in)solubility in a range of solvents, three\nmonomers could notably be polymerized in the green solvent <i>N</i>-butyl-2-pyrrolidone (NBP), in which soluble polymers were\nobtained. Dithiobenzoate-mediated radical polymerization of all four\nmonomers led to polymethacrylates with theoretical number-average\nmolecular weights (<i>M</i><sub><i>n</i></sub>) of up to 45 kg/mol and single-detection size-exclusion chromatography <i>M</i><sub><i>n</i></sub> values of up to 24 kg/mol.\nThe purified polymers show thermal stabilities in the range of 300–350\n°C and high glass-transition temperatures, up to 220 °C.