The Study On The Transparency Of Electrospun Nanofibrous Membrane And Alcohol Detection

Electrospun nanofibrous membrane has been widely used in optoelectronic devices,tissue engineering scaffolds,wound dressings,filtration and adsorption due to its flexible design,controllable structure,high specific surface area and high porosity.However,electrospun nanofiber membrane with a large number of light scattering sites formed by a large number of air-fiber interfaces and rough surfaces,which causes the visible light to undergo multi-level reflection at the air-fiber interface and increases the optical path of the incident light.So electrospun nanofibrous membrane is opaque due to the most incident light is lost through absorbing or scattering by the nanofibers,which limits the application of fibrous membranes.Therefore,research on the transparency of electrospun nanofibrous membranes through the material optimization and structural regulation can endow the fibrous membrane superior performance and application convenience,which can further expand its industrial application,upgrade product performance,and obtain visual fibrous membrane materials.In this paper,the refraction index of composite fibrous membrane is regulated by the composition and structural design of the original liquid,and the fibrous interface with excellent light transmission response is constructed to realize the specific detection of alcohol.The light propagation mechanism and response behavior of composite fibrous membrane are further studied,which lays a theoretical foundation and technical guarantee for the application of visual alcohol detection.This paper systematically completes the following three parts of work:1.In this chapter,a series of low refractive index polymers polyvinylidene fluoride(PVDF)with different concentrations are deposited on the surface of electrospinning polylactic acid(PLA)fiber membrane to successfully prepare hierarchical PLA/PVDF fibrous membrane materials.By means of scanning electron microscopy,infrared spectroscopy,X-ray diffraction and other characterization methods,the evolution process of electrospinning PVDF with different concentrations from microspheres to fibers is studied,and the influence of morphology changes on the visible light scattering behavior of hierarchical fibrous membranes is clarified.The air-fiber interface with high refractive index difference in PLA/PVDF fiber is replaced by alcohol-fiber interface with low refractive index difference through alcohol infiltration,which reduces the light loss at the interface and increases the light transmittance of fibrous membrane to T=91%.The construction of this hierarchical fibrous membrane provides the feasibility of alcohol dipstick based on light transmittance response,and provides a new idea for naked-eye detection of alcohol.2.Due to the large discrepancy of refractive index between PLA and alcohol,the thickness of the fibrous membrane is limited,and the mechanical properties of the membrane need to be further improved.Therefore,on the basis of the above work,in this chapter,a fluorine-rich oligomer,perfluorodecyltriethoxysilane(FAS-17),is introduced to modify the PVA matrix through the side-group engineering strategy.Then PVA@FAS-17 composite fibers are successfully prepared by controllable electrospinning and deposited on the surface of PVDF-HFP fibers to obtain PVDF-HFP/PVA@FAS-17 hierarchical membrane.The surface morphology and structure of the composite fibrous membrane are studied by scanning electron microscopy,atomic force microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy and infrared spectroscopy.It is found that fluoride silane is hydrolyzed to produce highly chemically active silicon hydroxyl groups,and reacts with hydroxyl groups of PVA to obtain fluorine-containing side groups,which reduces the refraction index of the spinning system.After alcohol treatment,the light transmittance of the membrane reaches84%.In addition,the fibrous membrane can also monitor alcohol vapor and trace alcohol in water,and ensure the stability of alcohol detection after multiple cycles of alcohol rinsing,sandpaper wearing,and ultrasonic cleaning.3.In order to obtain an alcohol dipstick that can quantitatively detect alcohol,we designed and developed a transparent photonic film with intelligent responsiveness by combining evaporation-induced co-assembly and electrospinning technology.In this chapter,PAN/PVA@GLU core-shell fibrous membrane is prepared by electrospinning using polyacrylonitrile(PAN)as the core layer and polyvinyl alcohol@glucose(PVA@GLU)as the shell layer.Then,the fibrous membrane material is impregnated with cellulose nanocrystalline/polyvinyl alcohol/glucose(CNC/PVA/GLU)suspension,and transparent photonic films are successfully prepared by evaporation-induced co-assembly.The morphologies of core-shell nanofibers and the structure of transparent photonic films are studied by means of scanning electron microscope,transmission electron microscope and polarizing microscope.The results demonstrate the transparent photonic film can respond to cyclic changes in relative humidity,that is,their structural color exhibits a reversible change from yellow-green light to colorless.In addition,the films could be used as alcohol dipstick with quantitative detection ability by choosing solvents with different polarities such as alcohol mixed with water to immerse this film.