Preparation, Characterization And Application Of Functionalized Polymer-based Porous Microspheres

Due to their low density, synthetic diversity and facile functionalization, porous materials developed from organic polymers, including porous carbon and porous organic polymers have drawn great research interest in recent years. The main efforts in this area focus on the design and synthesis of new functionalized porous materials and their applications in the fields of gas storage, heterogeneous catalysis, organic electronics and optoelectronics. Accordingly, the main task of this thesis is to design and synthesize functionalized porous microspheres based on organic polymers and to apply them in the area of dye adsorption, heterogeneous catalysis, molecular detection and light-harvesting. The detailed results of each part are listed as follows:(1) Mesoporous magnetic Co-NPs(nanoparticles)/carbon nanocomposites were synthesized by carbonization of polyacrylonitrile (PAN) microspheres entrapped with cobalt salt for the first time. The structure and morphology of the porous magnetic nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and N2adsorption-desorption technique. The nanocomposites possess very high saturation magnetization (Ms is up to133emu/g), near-zero remanence, and very low coercivity (He is down to0.023kOe). Meanwhile, the nanocomposites have mesoporous structure with average pore size of4nm and high specific surface area of232m2/g, which can be tuned by changing the carbonization conditions. Using methyl orange (MO) as model pollutant in water, the mesoporous magnetic nanocomposites showed good adsorption capacity of380mg/g, and the absorbed MO could be easily released in ethanol. The esoporous nanocomposites were facile separated from solution under external magnetic force, and over85%adsorption capacity for MO could be retained after five adsorption/desorption cycles.(2) Conjugated nanoporous polymer colloids (CNPCs) consisting of covalently cross-linked poly(p-phenyleneethynylene) networks were synthesized by using the Sonogashira coupling reaction in a toluene-in-water miniemulsion. The synthesized CNPCs having a uniform particle size distribution exhibit high porosity with a specific surface area of421m2/g and a dual distribution of pore size in the micropore and mesopore ranges. They are amenable to postfunctionalization and enhancement of their dispersibility in solvents, and retain their native photoluminescence. The modified CNPCs allow for in situ incorporation of palladium nanocrystals to form the Pd@CNPC composite materials. The Pd@CNPCs are validated to have excellent catalytic activity, outstanding reusability, and exceptionally high TOF (44100h-1) for the Suzuki-Miyaura coupling reaction.(3) A novel multifunctional conjugated nanoporous polymer colloid (CNPC) combined with metal nanocrystals has been synthesized using the Sonogashira coupling reaction in a toluene-in-water miniemulsion. It is composed of a poly(phenyleneethynylene)(PPE) network that is covalently inlaid with the locked-in Fe3O4nanocrystals. The Fe3O4@CNPC has a narrowly distributed size and uniform morphology, preserves the advanced porosity and fluorescence emission of the conjugated polymer network, and shows rapid magnetic response and high catalytic activity. The magnetic content can be controlled during the synthesis. This is accompanied by a corresponding enhancement of the size and surface area of the mesopores. In view of those characteristics, Fe3O4@CNPC is able to behave as fluorescence sensor for the detection of phenolic compounds. Acetaminophen (APAP) has been used as a model compound and the test results demonstrate that the Fe3O4-catalyzed oxidation of APAP takes place within the pores of the PPE network in the presence of H2O2. The oxidized intermediates are reactive radicals and can remove electrons from the p-conjugated PPE network, eventually leading to a decrease or even quenching of its fluorescence. Since the multiple functions of Fe3O4@CNPC fully cooperate, it produces a rapid optical response and superior sensitivity for the detection of APAP at micromolar concentrations.(4) A novel light-emitting conjugated nanoporous polymer colloid (CNPC) with tetraphenylethene (TPE) as a building block has been synthesized by using the Sonogashira coupling reaction in a toluene-in-water miniemulsion. Solvent-hydrothermal treatment was used in the preparation process, which successfully enhanced the porosity and luminescence. Treated sample preserves high porosity and a tunable dual distribution of pore size. The interlocked network successfully restricts the rotation of the phenyl units, promotes π-conjugation, and improves luminescence activity. A light-harvesting system with designable donor-acceptor compositions was synthesized with the energy-accepting nile red molecules. Excitation of the TPE-CNPC skeleton leads to emission from nile red, while the fluorescence from TPE-CNPC itself is quenched as a result of energy transfer from the TPE-CNPC framework to nile red, which shows quick and efficient characters. In view of the solution processability, composite TPE-CNPC/PVA films were prepared using casting method. Doping of the films with fluorescence dyes enabled fine-tuning of the emission colors and a white light emitting film was obtained.