Study On Nanocolorants And Photoswitchable Fluorescent Nanohybrids

In general, those pigment particles, composite particles of dyestuffs or pigment and their dispersions with dimension less than 100 nm can be all defined as nanocolorants. Besides the advantaged applications in conventional coloration for polymers, painting & coating and cosmetics etc, nanocolorants and their aqueous dispersions could be directly utilized in color ink-jet printing and likely cause revolutionized change for the color image-printing industry. However at present, the preparing study of nanocolorants still only focused on the traditional physical submicronization in our country, which is a high energy-consumption, high-cost approach. In this dissertation, one of our main objectives is to introduce a facile, low-cost method for preparation of a class of nanocolorants with excellent chromatic property of dyes and superior durability of organic pigments.Through the stop-press searches and investigating on the all-around references and documents, miniemulsion polymerization is concluded as the most feasible approach for the preparation of nanocolorants. Although Germany BASF Corporation briefly reported this approach for the preparation of nanocolorants we cannot acquire the key techniques and formulation about the generation of nanocolorants. Therefore the modified miniemulsion polymerization process for achieving the objective was studied by ourself, in which include the following: 1) the controllable preparation for the steady miniemulsion dissolved with high-content red, yellow, blue and green hydrophobic dyes. Because the stabilized miniemulsion including homogeneous size-adjustable minidroplets is the precondition for the form of high-quality nanoparticles, we should firstly obtain the formation rule of this given kind of miniemulsion; 2) to design the architecture of the high- performance nanocolorants and implement the modified miniemulsion polymerization process, in which are involved with many research issues as: effects of diverse hydrophobic dyes on the polymerization process, effects of diverse initiator and polymerized temperature&time, effects of polar monomers on the polymerization process and product, effects of the amount of dyes dissolved in styrene, significance of the crosslinking of matrix polymer, etc; 3) a series of characterization and performance test as follows: to evaluate whether all used dyes be incorporated in the nanoscale polymeric matrix, morphology of the nanocolorant particles and particle-size distribution, retaining stability of dyes in polymeric matrix, UV-Vis spectra analyses, evaluation of apparent chromaticity and photostability/ weatherability of nanocolorants, analyses for the heat stability and migration fastness of nanocolorants, etc. In addition, the preliminary works for the obtained nanocolorants & aqueous dispersions to be used in color ink-jet ink and color resist of CF were accomplished in this dissertation, which included correlative theory study and some experimentals.In the same way, the photoswitchable fluorescent nanohybrids based on spirobenzopyran were fabricated in the dissertation, in which hydrophobic spirobenzopyran and the matched fluorescent dyes are intermolecularly hybridized and embedded in the nanoscale crosslinked polymeric matrix. The obtained nanohybrids with high relative fluorescence quantum yield (Q) exhibited superior fluorescent photoswitchable performance due to the efficient photoinduced intermolecular energy transfer, and also the thermal stability of photomerocyanine was improved. So the type of nanohybrids may be developed individually addressable nanoscale devices with light.The photoswitchable fluorescent supramolecular systems based on diarylethenes have been received much attention in recent years owing to their promising applications in erasable media for ultrahigh-density optical data storage, photoswitching devices, and fluorescent biological markers. However, the previous efforts have almost focused on the covalently linked supramolecular systems with A-L-B architecture, there is still main disadvantage e.g. trouble in design and synthesis. In this dissertation, we developed a rather simple noncovalent approach to assemble a new type of photoswitchable fluorescent nanohybrids with quasi A-L-B supramolecular architecture, in which both of the essential components are assembled and intermolecularly hybridized in the nanoscale seeded polymeric matrix via a modified miniemulsion polymerization process and then achieved a modified or biocompatible shell by a seeded polymerization technique. Besides the study on how to perfectly implement the fabricating process, we emphatically investigated the mechanism of photoinduced intermolecular energy transfer from fluorescent molecules to photochromic component and how to enhance the efficiency of energy transfer, etc.The developed method of "modified miniemulsion polymerization process combining with seeded polymerization technique" in this dissertation extends the preparation for core-shell-type nanoparticles. Accordingly, a new class of high-performance core-shell-type fluorescent nanospheres which emit orange, yellow, green and cyan light respectively, have been fabricated.