Preparation, Characterization And Application Of New Functional Polymer Microspheres

As a novel kind of functional polymer materials, polymeric microspheres have been widely studied due to their great value in various application fields, such as biology technology, medical engineering, chemical industry and electronic information, etc. The purpose of this thesis is to develop new methods to prepare novel functional polymeric microspheres and their applications. Firstly, a suitable precipitation polymerization method was chosen to prepare monodispersed polymeric microspheres. After surface modification, their applications have been conducted in our experiment. The main contents and results are as following:1. We prepared high hydrophilic PMAA nanohydrogels from commercial methacrylic acid and synthesized N, N’-bis(acryloyl)cystamine crosslinker utilizing free radical reaction via distillation-precipitation polymerization method. Dispersion light scattering(DLS), transmission electron microscope(TEM) and scanning electron microscope(SEM) studies revealed that as-prepared nanohydrogel microspheres have uniform size, narrow monodispersedsized dispersion and high hydrophilicity. Turbidity change showed that the nanohydrogels could be quickly degraded in the presence of reducing agent. Futher more, gel permeation chromatography (GPC) studies also revealed that the polymer degraded into polymeric chains with low molecular weight. Ultraviolet absorption spectrometry (UV) confirmed that nanohydrogels have high drug loading capacity and entrapment efficiency. More interesting, the drug releasing experiment detected that the nanohydrogels exhibiting an obvious pH/redox dual-responsive controlled drug release capability, and with obvious varying responses to dithiothreitol (DTT) and glutathione (GSH). Subsequently, the cell counting kit-8(CCK-8) assay cell experiment further verified the targeting drug delivery efficacy, and fluorescence microscope demonstrated the DOX-loaded nanohydrogels could be taken up quickly by human glioma (U251MG cells) and then biodegraded to release the loaded drugs. We also prepared biodegradable polymeric hollow microspheres via two-step distillation-precipitation polymerization method. First, we prepared uncrosslinked PMAA polymeric microspheres as core, and then coated them with a layer of disulfide-crosslined polymer shell, subsequently dissolved the uncrosslinked core using ethanol as a gentle condition. Besides, we also prepared core-shell composite microspheres with Fe3O4 magnetic colloidal nanocrystal cluster (MCNC) cores and biodegradable polymer shells.2. Poly[N-(2-hydroxypropyl)methacrylamide-co-methacrylic acid](PHPMA-co-MAA) nanohydrgels were prepared via distillation-precipitation polymerization method, then we synthesized aminated folic acid molecules, and modified it to the surface of nanohydrogels via amidation reaction. Dispersion light scattering (DLS) and transmission electron microscope (TEM) studies revealed that as-prepared nanohydrogels have uniform size, narrow dispersion and well hydrophilicity. Gel permeation chromatography (GPC) studies detected that polymer could be degraded into polymeric chains possessed two polymer building units with low molecular weight. Both fourier transform infrared spectroscopy (FTIR) and ultraviolet absorption spectrometry (UV) confirmed the successful conjugation of folic acid molecules to the surface of nanohydrogels. The cell experiment demonstrated that HPMA monomer makes the nanohydrogels having better biocompatibility compared with pure PMAA nanohydrogels. Besides, the conjugated folic acid molecule makes the nanohydrogels have obvious target therapy efficacy towards Hela cells that with abundant folate receptor. Futher more, the studies to the hydrophobic anti-cancer drug paclitaxel also extend the application scope. We also prepared polyethylene glycol methacrylate-co-methacrylic acid (POEGMA-co-MAA) nanohydrogels via one-pot distillation-precipitation polymerization method.3. Polyphosphazene nanoparticles were designed and prepared as a novel heterogeneous catalyst. We realized high efficiently conversion from fructose to HMF (HMF yield of97.2%within0.5h) using DMSO as solvent. First, we prepared polyphosphazene micro spheres within different solvents, deacid reagents and monomer molar ratios. Dispersion light scattering(DLS), transmission electron microscope(TEM) and scanning electron microscope(SEM) studies all revealed that as-prepared microspheres have uniform size, narrow monodispersedsized dispersion. Catalysis experimental results demonstrated the microspheres have high catalatic activities that are affected by their monomer molar ratio. Subsequently, we modified the surface of microspheres respectively with HCCP, BPS monomer or benzoyl chloride. Catalysis experiment results confirmed that the P-Cl groups in HCCP unit are essential to their catalytic activities. We further studied the catalytic activities of microspheres with different monomer molar ratios at various substrate concentrations, and compared with homogeneous catalyst such as HCl or HCCP monomer. To our surprise, the heterogeneous catalyst surpassed its homogeneous counterpart such as HCl and HCCP. Herein, we put forward a novel proposal catalysis mechanism that the reaction may undergo a relative stable transition state to form an intermediate. So we prepared other two kinds of polyphosphazene nanoparticles to investigate the impact of inner chemical composition and electronic properties of polymer microspheres to the catalytic activity. We also designed competition reactions adding stoichiometric glycerol or dihydroxyacetone, and the results showed that the P atom on the surface of microspheres has strong interaction with the O atom of hydroxyl groups and ketone groups in the sugars. We also prepared polymer nanotubes, their catalytic activity showed that the materials with other form also could be effective because the catalytic active spots are mainly on their surface. Besides, we further prepared magnetic core-shell composite microspheres, such as Fe3O4@PZS with Fe3O4magnetic colloidal nanocrystal cluster (MCNC) cores and polyphosphazene shells, and PZS@Fe3O4@PZS sandwich-type composite microspheres, which could be used as magnetic solid catalyst for more facile separation and recycle.