Synthesis of mono functional carboxylic acid poly(methyl methacrylate) in aqueous medium using sur-iniferter. Application to the synthesis of graft copolymers polyethylene-g-poly(methyl methacrylate) and the compatibilization of LDPE/PVDF blends

Carboxylic acid mono functional poly(methyl methacrylate) was prepared by emulsion photopolymerization using 4-diethylthiocarbamoylsulfanylmethyl benzoic acid (DTBA) as sur-iniferter agent. DTBA is efficient to obtain mono functional polymers with a linear evolution of Mn vs. monomer conversion up to 60%. Beyond 60% monomer conversion, Mn decreases drastically and addition of a supplementary surfactant seems to disturb the effect of sur-iniferter. Secondly, an α-functional polymer presenting a Mn=43500 g/mol, a polydispersity index Ip=2.67 and a functionality fCOOH=98% was grafted in the molten state onto a statistical copolymer of ethylene and glycidyl methacrylate and the amount of PMMA grafts was about 10 wt%. In a final step, the graft copolymer was used as emulsifier in LDPE/PVDF blends. Blends including the graft copolymer present a better interfacial adhesion and a reduction of the size of the dispersed phase in comparison with blends without additive.