Synthesis of PPEGMEA-g-PMAA densely grafted double hydrophilic copolymer and its use as a template for the preparation of size-controlled superparamagnetic Fe3O4/polymer nano-composites

A series of well-defined amphiphilic densely grafted copolymers, containing polyacrylate backbone, hydrophobic poly(methoxymethyl methacrylate) and hydrophilic poly(ethylene glycol) side chains, were synthesized by successive atom transfer radical polymerization. Poly[poly(ethylene glycol) methyl ether acrylate] comb copolymer was firstly prepared via the grafting-through strategy. Next, poly[poly(ethylene glycol) methyl ether acrylate]-g-poly(methoxymethyl methacrylate) amphiphilic graft copolymers were synthesized via the grafting-from route. Poly(methoxymethyl methacrylate) side chains were connected to the polyacrylate backbone through stable C-C bonds instead of ester connections. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions were in the range 1.38-1.42. Poly(methoxymethyl methacrylate) side chains were selectively hydrolyzed under mild conditions without affecting the polyacrylate backbone to obtain the final product, poly[poly(ethylene glycol) methyl ether acrylate]-g-poly(methacrylic acid) densely grafted double hydrophilic copolymer. Finally, these double hydrophilic copolymers were used as templates to prepare superparamagnetic Fe3O4/polymer nano-composites with narrow size distributions via an in situ co-precipitation process, which were characterized by FT-IR, TGA, DLS and X-ray diffraction in detail. The size of the nano-composites can be controlled in a certain range by adjusting the length of the poly(methacrylic acid) side chains and the weight ratio of copolymer to Fe3O4 nano-particle used.