flame retardant, DOPO is also attractive because PH bond can be easily modified into PN, PO, or PC bonds, leading to improved thermal stability. [5][6][7][9][10][11][12] DOPO has been successfully used as an additive in many polymers (additive strategy) such as epoxy resins, [13,14] polyurethane, [9] acrylonitrile-butadiene-styrene copolymers, [15] polyamide, [16] and poly(methyl methacrylate) (PMMA). [17] Alternatively, DOPO-based monomers have been used to prepare matrices with chemically bound flame-retardant groups (reactive strategy) by step polymerization, like epoxy resins, [18][19][20][21] polyurethane, [22] poly(ethylene terephthalate), [23] polyamide, [24] ethylenevinyl acetate copolymer, [25] and polysulfone. [26,27] Nevertheless, to the best of our knowledge, only one study has been reported about the synthesis and application of DOPO-derived acrylate monomer for the preparation of flame resistant thermoplastic matrix by free radical polymerization. [28] More precisely, the latter monomer was first derived from acryloyl chloride with DOPO covalently linked as side group, then copoly merized with methyl methacrylate (MMA).Because of the very limited number of available studies, there is a need for new flame-retardant monomers able to react with common monomers via free radical polymerization. While bringing flame-retardant properties, these monomers should also preserve mechanical properties of final polymeric materials. The first requirement regarding mechanical properties is generally that the materials exhibit a high enough glass transition temperature (T g ) as compared to the conditions of targeted application. Indeed, when flame-retardant additives are blended with thermoplastics, they often act as plasticizers and consequently lower the T g of the final material, which may be a serious drawback. Such effect has been reported for DOPO. [17] Thus, the reactive strategy appears promising for providing efficient flame-retardant properties while limiting undesirable plasticizing effect.This work aimed at exploring a reactive strategy involving the design and the use of functional monomers with DOPO pending groups for including significant amounts of phosphorus in the material while keeping high enough T g . To that goal, DOPO was used as the precursor of the flame-retardant moiety and was covalently linked to methacrylate groups by aliphatic hydrocarbon spacers with number of carbon atoms ranging between 3 and 11 (Figure 2). Chemical structure and purity of the prepared novel phosphorus-containing methacrylic monomers were verified by combining several NMR Phosphorus-Containing MethacrylatesA two-step synthetic procedure is designed for preparing new flame-retardant methacrylic monomers containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as a substituent side group. DOPO and methacrylate moieties are linked by linear aliphatic hydrocarbon spacers (3 to 11 carbon atoms). Copolymerization with methyl methacrylate is carried out leading to copolymers containing between 2 and 10 wt% ...

From a set of around 100 phosphorus-containing polymers tested in pyrolysis–combustion flow calorimetry, the contributions to flammability of two phosphorus-containing pendant groups (called 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and PO3) were calculated using an advanced method previously proposed and validated. The flammability properties include total heat release (THR) and heat release capacity (HRC) measured in standard conditions, i.e., anaerobic pyrolysis and complete combustion. The calculated contributions are in good agreement with the main modes of action of both phosphorus groups, i.e., flame inhibition for DOPO and char promotion for PO3. Moreover, the results provide first conclusions about the cooperative interaction between phosphorus and nitrogen, as well as the influence of the architecture of tested co-polymers.

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