Study On Photosensitive Sensors Of Coumarin

The smart amphiphilic polymers are causing extensive attentions since they can self-assemble nanostructures that used widely in the reaction vessel, drug nano-carriers, the catalyst and enzymes and other biological macromolecules protective carrier. Smart polymers means the polymer structures can make a series of chemical/physical changes when subjected to external conditions (temperature, pH, light and ionic strength, etc.), resulting in the polymeric self-assembly changes.In this dissertation, the light control was introduced to study the self-assembly of coumarin based on amphiphilic polymers, and the study was divided into two parts:1.The water-soluble amphiphilic random copolymer of P(DMA-co-VBC) with coumarin pendants has been designed to investigate the photo-induced dynamic association of coumarin pendants within polymer micelles in aqueous solution. Methods of UV (solution transmittance, absorption spectrum), fluorescence spectra, DLS and AFM were applied. The time-dependent PD changes in the photo-dimerization experiments showed saturating behaviours with intensity-independent of PDmax values at 28,44,92,85,36,35,32 and 31% for 254,288,320,360,400,500,650 and 900 nm irradiations, respectively. The irradiation experiments at λ.< 300 nm announced the occurring of an asymmetric equilibrium of photo-dimerization and photo-cleavage, and the photo-dissociation extent of coumarin dimers declined with the enhancement of 254 nm irradiation intensities at the used conditions. Finally, three kinds of alternating light were selected, i.e.320 and 254 nm,360 and 254 nm,650 and 254 nm irradiation experiments. Result show that coumarin side groups can occur reversible dimerization. At the same time, a significant emission band at 445 nm (I2) evidently emerged as against the disappearance of emission band at 385 nm (I1) during the photo-dimerization, and the time-dependent I2/I1 changes in the reversible photo-dimerization cycles showed a waved increase as a function of irradiation cycles, indicating the waved increasing hydrophobic association of coumarin pendants within polymer micelles.2. Two amphiphilic random copolymers of PDMV and PDMS were prepared, methods of ultraviolet spectrophotometer (UV), fluorescence spectroscopy (FL), dynamic light scattering (DLS) and atomic force microscope (AFM) were applied to investigate the micellization behaviors of PDMV and micellar mixtures of PDMS and PDMV with the temperature changing. The test results showed that PDMV (before and after cross-linking) and the micellar mixture of PDMV (before and after cross-linking) and PDMS afforded lower critical phase transition temperature (LCST) behaviors, but the latter showed a more broad transmittance changes at the LCST temperature. The polymer micelles were also visualized by the atomic force microscope (AFM).