Preparation Of Photofunctional Molecules/Layered Double Hydroxides Composite Materials And Study On Their Intelligent Response

Intelligent optical functional materials, which respond to external environmental stimuli, have attracted considerable attention from both theoretical study and practical application, owing to their great prospects in fluorescent switches and optical devices. The stimuli-responsive optical functional materials with ordered molecular orientation are more beneficial to show excellent responsive behavior compared with irregular ones. Therefore, the design of photofunctional materials with a high orientation is significant to achieve sensitive and stable stimuli-response. In this dissertation, based on the structural properties of layered double hydroxides (LDHs), we have fabricated the BTBS@PAA/LDH and (ICG-SDS/LDH)/pNIPAM/PVA/R6G composite film, by the use of layer-by-layer (LBL) assembly and solvent evaporation technique. The piezochromism performance and photodeformable behavior of these two film materials were investigated. The main research contents and results are as follows:1. A flexible ultrathin film (UTF) was fabricated via layer-by-layer (LBL) assembly of a sodium polyacrylate (PAA) modified styrylbiphenyl derivative (BTBS) and MgAl-LDH, which exhibits pressure-responsive fluorescence performance with high sensitivity and reversibility. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and small angle XRD show that the UTF possesses a homogeneous surface and an ordered structure. Interestingly, the fluorescence intensity of UTF at??450 nm enhances systematically as the external pressure increases in the range 0-12 MPa, accompanied with improved quantum yield (QY) and lifetime. A simple treatment at 70 ? could recover the fluorescence performances of the UTF. FT-IR and small-angle XRD indicate that the UTF undergoes a contraction-expansion transformation in the compressing-recovering cycle. The external pressure leads to a constringent state of BTBS, which inhibits the non-radiative transition of BTBS and effectively promotes its fluorescence performances. Moreover, the UTF displays good reversibility and repeatability toward pressure, which may find potential use in pressure sensors.2. The (ICG-SDS/LDH)/pNIPAM/PVA/R6G film has been fabricated via the solvent evaporation method, which shows a uniform morphology and self-supported property. Small-angle XRD and FT-IR indicate that the ICG and SDS are intercalated into the interlayer region of LDHs; the stability of intercalated ICG is largely promoted, which results in largely-enhanced photothermal conversion efficiency (irradiation at 808 nm). Subsequently, the polymer pNIPAM shows a thermally induced contraction, which leads to the film deformation. Moreover, with the introduction of R6G, the obtained film material exhibits observable photo-deformation in dark environment.Therefore, two kinds of stimuli-responsive composite materials were prepared through LBL and solvent evaporation method, respectively, which can be potentially used in photofunctional sensors and switches.