Synthesis of polyester thermosets via internally catalyzed Michael-addition of methylene compounds on a 2-(trifluoromethyl)acrylate-derived building block

Abstract : The Michael-addition reaction of methylene compounds has been known and used for more than 120 years in organic chemistry synthesis. We report herein a new type of application for this reaction: the preparation of thermosets by catalyst-free bis-Michael addition. In this study, the addition of various methylene C-nucleophiles on tert-butyl 2-(trifluoromethyl)acrylate in presence of a tertiary amine was preliminary evaluated. Then, a tris-2-(trifluoromethyl)acrylate monomer incorporating a tertiary amine was synthesized and used with methylene monomers to prepare innovative polyester networks at temperature going from 25 °C to 100 °C. Finally, the resulting fluorinated carbon-Michael networks were characterized by FTIR, differential scanning calorimetry, thermal gravimetry, dynamic mechanical and swelling analyses. These thermosets exhibited high gel content (>86 %) and good thermo-mechanical properties with a rubbery plateau above 7 MPa and a glass transition temperature above 44 °C. The material thermal properties could be adapted to a targeted application (binder or coating) by the choice of the methylene compound used in the thermoset formulation.