Graft copolymers having hydrophobic backbone and hydrophilic branches - 27. Nanosphere formation in copolymerization of methyl methacrylate with poly(ethylene glycol) macromonomers

Polymeric nanospheres consisting of poly(methyl methacrylate) (PMMA) cores and poly(ethylene glycol) (PEG) branches on their surfaces were prepared by free radical copolymerization of methyl methacrylate (MMA) with PEG macrom onomers in ethanol/water mixed solvents. PEG macromonomers having a methacr yloyl (MMA-PEG) and p-vinylbenzyl (St-PEG) end group were used. It has beco me clear that the obtained polymer dispersions form three kinds of states, particle dispersion (milky solution), clear solution, and gel/precipitation . It was found that the reaction parameters such as MMA concentration, mole cular weight, and concentration of PEG macromonomers, and water content can affect nanosphere formation in a copolymerization system. The water volume fraction of mixed ethanol/water solvents affected the particle size of the nanospheres. These differences in the formation of nanospheres were due to the solvophilic/solvophobic balance between the copolymers and solvents du ring the self-assembling process of the copolymers. The sizes of nanosphere s can be controlled by varying concentration of PEG macromonomer and water content in solvents. (C) 2000 John Wiley & Sons, Inc.