The Photochromism And Photoresponse Mechanism Of Spiropyran In Different Surroundings

As a dynamic material, spiropyrans have recently received considerable attention to different specific areas, such as photoelectric device, data storage, logic gates, ion recognition, self-assembly, controlled release and bio-image. These applications are based on the reversibly switching between two forms:the colorless ring-close form SP (spiropyran) and the colored ring-open form MC (merocyanine). The two reversible isomers have different remarkable characteristic in the ultraviolet-visible (UV-vis) absorption spectroscopy, dipole moment, dielectric constant, geometrical structure and coordination, self-aggregation property. The switch is triggered by multiple stimulants, e. g. light, solvent, electricity, temperature, mechanical force etc. On the other side, the loss of performance overtime called "fatigue" of spiropyran is inevitable, due to the chemical degradation which primarily caused by oxidation in the conversion between SP and MC. The fatigue resistance is also elemental to spiropyran materials. Therefore, the surroundings are of great importance for the application of spiropyran. The main researches and conclusions of the thesis are as follows:1. Using 2,3,3-trimethyl-3H-indole and 5-nitrosalicylaldehyde as the main raw material, the spiropyran derivertives that contain different N-substituent on indoline fragment have been synthesized, such as the spiropyrans have -OH moiety (SPOH),-CH(OH)Cl moiety (SP(OH)Cl), methacrylate moiety (SPMA), trithiocarbonate moiety (SP-RAFT). The structure and component of the spiropyran derivertives have been characterized by FT-IR,1H NMR and EI-MS.2. According to the the UV-vis spectra, the polarity of the solvent played a crucial effect on the absorbance of SPOH and SP(OH)Cl, employing the relative polarity and Reichardt’s empirical solvent polarity parameter (Er). The MC forms in different solvent lead to a blue shift with increasing polarity, which is usually called "negative solvatochromism". SPOH or SP(OH)Cl in the solvent with high viscosity such as ethylene glycol, polyethylene glycol have different photochromism when comparing with that in monohydric alcohol, which may be influenced by the structure and hydrogen bonding of the solvent molecule. The fatigue resistance is also investigated by the value of cyclability (Z50).3. Combining the self-emulsifying process with core-shell emulsion, the micelles containing macro-emusifier of acrylic acid (AA) constitutional unit on shell and spiropyran in core have been prepared, named as PMBA-PMH-SPOH, PMBAT-PMHSP and PMAA-PMSP emulsion, respectivly. The micelle particles have been characterized by Dynamic Light Scattering (DLS), SEM and UV-vis spectrum. The emulsion exhibits fast response to UV light. During the thermal fading process, the emulsion emerges continuous variable pattern on the surface. At the same time, the colored emulsion is light-guided and keeps swimming to the light. These phenomenom is probably initiated by the effect of MC on the electrostatic field of the micelle, which is a process of non-equilibrium self assebly. It gives a preliminary analysis on the process and behavior of spiropyran emulsion. Since the self-emulsifying technique is widely used in medicine, the micelles that are light-guided and light-driven have great potential in the next-generation drug delivery.4. The photochromism of SP-RAFT in solution has been characterized by UV-vis spectrum. In the observation of SP-RAFT in hexane, the MC forms aggeregate and keep growing during the thermal fading process until they return to SP form. The increasing diameters of the aggregates are determined by DLS. When exposed to magnet, the aggregates preceed to a circumfluence in hexane. When exposed to UV light, the aggregates move to the lighted spot and showed light-guided performance. Through the controlled "living" radical polymerization of iV-isopropylacrylamide (NIPAM) that mediated by SP-RAFT, the photo-and thermal responsive polymer has been prepared. The dual sensitive properties have been characterized by UV-vis spectrum, the Lower Critical Solution Temperature (LCST) is 28.0℃. The fatigue resistance of the polymer is also determined by the value of Z50.