Synthesis of a New Phosphonated Dimethacrylate: Photocuring Kinetics in Homo- and Copolymerization, Determination of Thermal and Flame-Retardant Properties

In this work, we describe the synthesis of a new dimethacrylate phosphonate monomer by condensation of methacryloyl chloride with a phosphonate diol resulting from a radical addition of allyldiethyl phosphonate with 3‐mercapto propane‐1,2‐diol. The photochemical polymerization of this new monomer was first studied as a function of reaction temperature. The optimal conversion of the photopolymerization was 63% at 70°C. This new monomer is less reactive than the commercial dimethacrylate polyether of Bisphenol A, that we have used for copolymerization. The mechanical and thermal properties of the final material were studied as a function of dimethacrylate phosphonate monomer content. The ultimate conversion slightly decreases (from 72 to 55%) and the glass transition temperature drops from 44 to –26°C when the phosphorus content increases. The addition of phosphorus leads to an improvement of the thermal and flame‐retardant properties, i. e. a significant decrease in the degradation rate (factor 4.5) and a high increase in the amount of residue that remained after combustion (15% for the 2.5% phosphorus copolymer). Moreover, the Limited Oxygen Index (LOI) is increased from 16.9 (0% P) to 21.5 (2.5% P).