Study On Synthesis And Self-assembly Of Polymethyl Methacrylate Graft With Polyethylene Glycol

Poly(methyl methacrylate) graft poly(ethylene glycol) (PMMA-g-PEG) copolymers were prepared by radical copolymerization of methyl methacrylate (MMA) and poly(ethylene glycol) macromonomer (MA-PEG) with a methacryloyl end group in N,N-dimethylformamide (DMF). The structures and molecular weights of the PMMA-g-PEG copolymers were characterized by nuclear magnetic resonance (NMR), Fourier transformation infrared (FTIR) spectrometer and gel permeation chromatography (GPC). The results show that structures of the PMMA-g-PEG copolymer are clear. The molecular weight and distribution of PMMA-g-PEG has not clearly changed under different ratio of MA-PEG macromonomer to MMA. The thermal properties of the copolymer were investigated by differential scanning calorimeter (DSC) analysis. It was found that the PMMA-g-PEG copolymers have evident phase change. The phase change temperature and the value of phase change enthalpies are affected by changing content of MA-PEG. The phase change enthalpies were increased through increasing content of MA-PEG macromonomer.The micelle solutions of PMMA-g-PEG were prepared in the selective solvent such as DMF/H2O by self-assembly. The critical water content (CWC) was studied by ultraviolet (UV) spectroscopy for formation of micelles. The CWC was increased with content of PEG in the graft copolymer and decreasing concentration of copolymer solution. The morphologies of micelles were observed by transmission electron microscopy (TEM). Sphere and rod micelle could be found at different composition of PMMA-g-PEG copolymer when the water volume content was 18.3%. The bowl-shaped micelle was found through increasing water content. In the selective solvent such as dioxane/H2O, the shape of formed micelle changed to"loose"network structure. Pyrene was used as fluorescence probe to study critical micelle concentration (CMC) of the PMMA-g-PEG by fluorescence probe method. The quenching of pyrene in copolymer micelles by benzophenone was investigated. The results showed that the PMMA-g-PEG has low CMC and it was increased with decreasing content of PEG. Quenching constant of pyrene in copolymer micelles was affected by shape of micelles. The solubilization of pyrene from DMF/H2O mixed solvents to the micelles of PMMA-g-PEG copolymer was determined by fluorescence spectroscopy. The solubilization of pyerne depended upon water content in the mixed solvents.