DOPO-Based Phosphorus-Containing Methacrylic (Co)Polymers: Glass Transition Temperature Investigation

A 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% phosphorus. All homo- and copolymers exhibit a unique glass transition temperature (T-g ). A new group contribution for DOPO-based substituent is extracted that leads to reasonable estimations of T-g s of other published polymers. The Fox equation provides a good estimation of T-g s for most copolymers and for physical blends of poly(methyl methacrylate) (PMMA) and DOPO. When using monomers having three and four carbon atoms in the hydrocarbon spacer, the T-g of copolymers remains close to that of PMMA over a wide range of composition.