Study Of Zwitterionic Photosensitive Copolymer

Coumarin-containing acrylic acid monomer(CA) was synthesized,which could be used together with dimethylaminoethyl methacrylate(DM) and acrylic acid(AA) to synthesize the zwitterionic photosensitive copolymer poly(dimethylaminoethyl methacrylate–co-acrylic acid-co-4-methylcoumaryl acrylate) P(DM-co-AA-co-CA) via free radical copolymerization. Its structure was characterized by Fourier transform Infrared Spectroscopic (FTIR), Magnetic Resonance Spectrometer (1H-NMR), Gel Permeation Chromatography (GPC) and Differential Scanning Calorimeter (DSC).The copolymer could self-assemble into steady spherical micelles in the selective solvent THF/water with suitable initial copolymer concentration and water content. The self-assembly process and characteristic of P(DM-co-AA-co-CA) micelles were studied by UV spectrophotometer,Dynamic Laser light Scattering(DLS) and Transmission Electron Microscope(TEM). The results show that compared to add aqueous solution, the CWC decreased when add dropwise basic or acid aqueous solution into the copolymer THF solution. When increased the quantity ratio of CA moieties or the initial concentration of copolymer in THF also made the CWC decreased.The multi-sensitive of copolymer micelles were studied by Zeta Potential,Fluorescence spectrophotometer,UV spectrophotometer,Dynamic Laser Light Scattering(DLS) and Transmission Electron Microscope(TEM). The results show that in the range of pH 2.13-8.54, the UV absorbance and fluorescence emission intensity of micellar solutions increased with increasing of pH, and in the range of 8.54-12.46, both of them decreased with increasing of pH. Depending on the solution pH, these micelles can exist in two different micellar charge states and also exhibit an isoelectric point at around pH 9.73, around which the diameter of micelles became the smallest, and then it increased either with the pH increasing or decreasing. In basic solution, LCST of micelles decreased with increasing of pH.The stable emulsions were obtained with P(DM-co-AA-co-CA) micelles used as particulate emulsifier which homogenized with equal volume toluene as oil phase. This particulate emulsifier has the dual advantages of polymeric surfactant and particulate emulsifier. The stability of emulsions increased with the increasing of photo-dimerization degree, net charge of micelles and micellar solutions. Styrene-in-water (o/w) emulsion was also obtained in the same way after the homogenization. The emulsion was diluted and polymerized at 65℃to solidify the oil phase for SEM studies. The results showed that the nanoparticles were adsorbed at the surface of the solidified PS particles, which indicated that the self-assemble micelles were absorbed at the oil/water interface to prevent the coalescence of emulsion droplets.