Preparation And Application Of Cyclodextrins Supramolecular Functional Materials - From Macromolecules To Nanomaterials

Cyclodextrins (CDs) are the Second-generation supramolecular host molecules. Given the hydrophobic internal cavity and hydrophilic external surface of CDs, the special molecular structures can form supramolecular host-guest complexes with various hydrophobic molecules. Therefore, CDs are used in various fields, such as in electroanalysis, biotechnology, and environmental protection, because of their distinct physical and chemical properties. In this article, it was studied the combination between CDs and their water-soluble polymers with nanomaterials, and designed a variety of cyclodextrin functional materials with supramolecular recognition, expanded cyclodextrin nano-materials in the applications of electrochemistry and water treatment. This dissertation was divided into the following five parts:1. Electrospinning β-cyclodextrin/poly (vinyl alcohol) nanofibrous membrane for molecular captureA novel β-cyclodextrin/poly (vinyl alcohol) nanofibrous membrane (β-CD/PVAnfm) with the function of molecular capture was successfully prepared by electrospinning homogeneous aqueous solutions of β-CD and PVA. p-CD/PVAnfm was characterized by scanning electronic microscopy and Fourier transform infrared spectroscopy. The viscosity of β-CD/PVA solution increased with the concentration of β-CD and high viscosity of β-CD/PVA solution was beneficial to form more uniform nanofibers. The interaction between β-CD and PVA in the solution was studied by rheological measure and1H NMR. The rheological change of electrospinning solutions was attributed to the intermolecular hydrogen bonding between β-CD and PVA in the solution, which was confirmed by1H NMR. The electrochemical measurement showed that β-CD/PVAnfm could recognize small hydrophobic molecules such as ferrocene (Fc) by forming inclusion complexes. The molecular capturing ability of β-CD/PVAnfm increased with the amount of β-CD in the composite nanofibrous membrane. The results suggested that the composite nanofibrous membrane could be potentially applied to purification/separation processes, electrochemical sensor, drug delivery, and so on.2. Preparation of β-cyclodextrin functionalized polyacrylonitrile nanofibers and its adsorption for methylene blue A novel Polyacrylonitrile/β-cyclodextrin (PAN/β-CD) nanofibrous membrane (PAN/β-CDnfm) for molecular adsorption was successfully prepared by electrospinning from a homogeneous solution of β-CD and PAN in DMF. PAN/β-CDnfm with the different wt.%was characterized by scanning electronic microscopy, Fourier transform infrared spectroscopy and X-ray powder diffraction. The SEM results showed that the increasing concentration of β-CD in the fibrous membrane improved the fibrous morphology. The viscosity and conductivity of electrospinning solutions were influenced by the addition of β-CD. The studies of FTIR and XRD proved that β-CD molecules combined with the PAN nanofibers. In the adsorption study, methylene blue (MB) was used as a model molecule. By UV-vis spectrometry, PAN/β-CDnfm showed the efficient adsorption ability for MB via the formation of the inclusion complex with β-CD, which indicated that the β-CD functionalized nanofibers might be utilized in purification/separation processes, electrochemical sensor, drug delivery, and so on.3. Correlation of polymer-like solution behaviors with electrospun fiber formation of hydroxypropyl-β-cyclodextrin and the adsorption study on the fiberBased on our previous study of CD/polymer, the formation of hydroxypropyl-β-cyclodextrin (HPCD) nanofiber in electrospinning and the adsorption on HPCD nanofiber for organic molecule were studied. The properties of polymer-like solution from highly concentrated HPCD/N,N-dimethylformamide (DMF) solution revealed the formation of HPCD supramolecular aggregates. The entanglements of HPCD self-organized aggregates were one of the most important factors that significantly influenced fiber formation during cyclodextrin electrospinning. The HPCD self-organized aggregates entanglement concentration (Ce) was investigated. Analyzing the dependence of specific viscosity (ηsp) on concentration enabled the determination of the aggregates unentangled and entangled regimes for HPCD polymer-like solutions. The dynamic light scattering (DLS) measurements and the ’H NMR spectra of HPCD solutions confirmed the presence of considerable HPCD self-organized aggregates in high concentrated HPCD/DMF solutions due to the intermolecular hydrogen bonding. The scanning electron microscopy (SEM) showed the electrospinning morphology transitioned from regular beads to uniform fibers with the HPCD concentration increased. The dependence of the fiber diameter on the zero shear rate viscosity (η0) was determined. Static adsorption behavior of HPCD fibers was studied. Neutral red (NR) was a model organic molecule. The adsorption of NR onto HPCD fibers fitted the pseudo-second-order kinetic model. The equilibrium adsorption amount of NR was18.41mg g-1, and the apparent adsorption rate constant was9.83×10-4g mg-1min-1at25℃.4. Preparation and electrochemical behavior of water-soluble inclusion complex of ferrocene with β-cyclodextrin polymerA new water-soluble inclusion complex of ferrocene (Fc) with β-cyclodextrin polymer (β-CDP) was prepared by a facile strategy and characterized by1H-NMR spectroscopy, elemental analysis, powder X-ray diffractometry, thermogravimetry, UV-vis spectroscopy and cyclic voltammetry. Compared with Fc and the inclusion complex of Fc with β-cyclodextrin (Fc-β-CD), the solubility of ferrocene-β-cyclodextrin polymer (Fc-β-CDP) was greatly enhanced due to the water-soluble β-CDP host. The ratio of β-cyclodextrin (β-CD) unit in β-CDP to Fc was determined as1:1. At25℃, the dissociated constant of Fc-β-CDP was measured as3.65mM by UV-vis spectroscopy and cyclic voltammetry. The electrochemical properties of Fc-β-CDP in water were studied. The diffusion coefficients of oxidation state and reduction state were calculated as3.52×10-7cm2s-1and3.93×10-7cm2s-1. The resulting value of standard rate constant was measured as1.95×10-3cm s-1. The diffusion activation energy was calculated as21.8kJmol-1.5. Universal water-soluble cyclodextrin polymer-carbon nanomaterials with supramolecular recognitionFunctionalization of carbon nanomaterials (CNMs)(including fullerenes, single-walled carbon nanotubes, multi-walled carbon nanotubes (MWCNTs), and graphene sheets) dispersed in water with macromolecules was achieved by a one-step strategy using β-cyclodextrin polymer (CDP). CDP-CNMs were characterized by ultraviolet-visible, Raman, and Fourier transform infrared spectroscopies, transmission and scanning electron microscopies, and thermogravimetric analysis. These nanomaterials showed high solubility and stability in water because of the noncovalent interaction between CNMs and CDP. The supramolecular recognition abilities of CDP-CNMs were studied by cyclic voltammetry (CV). CDP-MWCNTs were also decorated by p-aminothiophenol (PATP) which formed inclusion complexes with the CDP. The conjugates (PATP-CDP-MWCNTs) were ideal templates for the highly efficient assembly of noble metal nanoparticles (Au and Pt) with dramatically different properties. Methanol oxidation of Pt-decorated PATP-CDP-MWCNTs in CV analyses indicated its potential application in direct methanol fuel cells, facilitating the feasibility of metal-decorated CDP-CNMs in real technological applications. This universal method of producing CNMs ftmctionalized with macromolecules is beneficial for investigating the structure-performance relationship of CNMs for designing compounds with specialized functions.