Preparation Of Functional Micro/nano Materials With Schiff-base Dynamic Covalent Bond

Nowadays,there is a large demand for polymer materials,especially functional polymers which become a research hotspot in polymer science.As morphologically functionalized polymers,micro/nano-scale polymers have the advantages of small size,large specific surface area,and low density,which have been applied to basic research in many fields such as environmental governance,biomedicine,and optoelectronic field.In mild condition,amino group(-NH2)and aldehyde group(-CHO)can form a reversible imine bond[-(C=N)-],named functional Schiff base bond,has good metal complexing ability and PH-responsibility.As a kind of dynamic covalent bond,Schiff base bond has both the rigidity of covalent bond and the adjustability of non-covalent bond.As one kind of popular functional group,it is widely used in fluorescent materials,chiral transfer,controlled drug release,etc.It is also a popular functional group for constructing functional polymers.Electrospinning and self-assembly method are commonly used to prepare micro/nano polymers.Electrospinning has huge number of positives,including clear mechanism,uncomplicated operation,and controllable product morphology.Micro/nano fiber membranes with uniform fiber diameters has good repeatability.Moreover,the micro/nano fiber membrane favors of functional groups exposing,which is convenient for efficient use.And self-assembly method has the beauty of safely operated,short reaction time,and good morphology repeatability.In this thesis,micro/nano functional polymer were constructed through Schiff base dynamic covalent bond by electrospinning and selfassembly methods.The major research contents are as follows:1.Biomass vanillin-derived polymer is successfully used as raw material for fabricating aldehyde-containing nanofiber membranes via electrospinning technique.Due to the superiority of electrospun nanofibers,the functional aldehyde groups are easily accessible and efficiently undergo Schiff-base reaction,followed by reduction reaction and protonation reaction.The three-step reactions enable the original hydrophobic membrane transform to hydrophilic nanofiber membranes bearing functional ammonium groups(NFMs-NH3+).The products were characterized by scanning electron microscope,Fourier transform infrared and water contact angle measurements.The NFMs-NH3+performed well in removal of anionic pollutants.The maximum adsorption amount towards MO and SDS reached 406.6 and 636.0 mg/g,respectively.The nanofibers exhibit high reusability and stability over six adsorption/desorption cycles.The prepared nanofibers also show certain adsorption towards nonionic organic pollutants,taking poly(vinyl alcohol)and sulfamethoxazole as models.2.The self-assembly of helical substituted polyacetylenes containing Schiff base dynamic covalent structure are prepared by self-assembly method.Chiral monosubstituted alkyne monomer was prepared by BocL(D)-alanine.Through solution polymerization,chiral monosubstituted poly acetylene chain with Mn=43700 mg/mol was obtained.After remove the protection group,the chiral monosubstituted polyacetylene chain contains free amino group,and can assembled with achiral monosubstituted polyacetylene with free aldehyde group.Through characterization analysis,the two monosubstituted polyacetylene chains assemble into a flower-like morphology,based on the Schiff base bond and non-covalent bond.The microstructure is affected by the reaction time,concentration and composition.Chiral transfer occurs in the self-assembly products,due to the formation of Schiff base bond.As Schiff base bond is pH sensitive,the self-assembly products has certain application prospects on chiral optical switch materials.