Studies On Photoresponsive O-nitrobenzyl-based Polymer Nanoparticles And Spiropyran-janus Materials

Light is an excellent trigger,owing to its fast responsiveness,non-invasiveness,and easy operation of wavelength,intensity,illuminated area and time.Recently,photoresponsive polymers were widely used in the field of controlled encapsulation and release,emulsifiers,and biointerfaces et al.In this dissertation,not only irreversible o-nitrobenzyl-based polymer nanoparticles for controlled release,but also the effect of photochromatic reversible spiropyran on the wettability of Janus materials were studied.The detailed contents and results are as follows:1.Photoresponsive o-nitrobenzyl-based nanogels:temperature-,pH-,and redox-responsive linear polymer nanogel precursors were intra/interchain cross-linked by photocleavable cross-linking agent.The multi-stimuli-responsive nanogels allowed for simultaneous encapsulation and stimuli-responsive selective release of hydrophilic and hydrophobic cargos.The hydrophobic cargos were released by increased temperature,weak acid,and UV irradiation,while the hydrophilic cargos were released in response to redox reagent.2.Photoresponsive o-nitrobenzyl-based polymer nanocapsules:responsive polymeric chains were cross-linked by photocleavable cross-linker on the emulsion template surface.Upon UV light irradiation,the monodisperse polymer nanocapsules underwent photodegradation efficiently.Hydrophobic cargo molecules were successfully encapsulated into the polymer nanocapsule,and then could be released in a controlled manner,namely,burst release by UV light irradiation,slow release by weak acid,and synergistic release by the combination of UV light and weak acid.3.Photoresponsive spiropyran-Janus composite nanosheets:hydrophobic spiropyran-containing polymer brushes were grafted onto one side of Janus silica nanosheets,while the other side was terminated with octyl groups.The Janus composite nanosheets could serve as a responsive solid emulsifier.After UV light irradiation,wettability of the Janus composite nanosheets was tuned from hydrophobic to amphipathic,and the stable water-in-oil emulsion formed.Upon another irradiation with visible-light,the Janus composite nanosheets were recovered hydrophobic,and the complete de-emulsification occurred.The emulsion stability can be remotely triggered in a reversible way by light.4.Photoresponsive spiropyran-Janus composite particles:hydrophobic spiropyran-containing polymer brushes were grafted onto the coarse hemispherical side of the as-synthesized Janus silica particles,and the other flat side was modified with hydrophilic imidazoline groups.The Janus composite particles were applied for the fabrication of robust light-responsive coatings.The polymer side directed toward the air.Under visible-light irradiation,the coatings were hydrophobic,and HeLa cells could be effectively captured onto the coatings;after UV light irradiation,the coatings became hydrophilic,and the captured cells were released.The processes of cell capture and release were reversible.