Preparation Of Conductive Polymer Nanofiber Membrane And Its Chemical Vapor Sensing Performance

Polymer nanofiber membrane prepared by electrospinning shows the merits of high porosity,large specific surface area,flexibility and lightweight,etc.In this study,carbon nano-fillers are evenly assembled on the surface of polymer nanofibers under the assistance of ultrasonication,thus forming a conductive network,and then a flexible conductive polymer nanofiber composite membrane composed of one dimensional nanofiber network is obtained.It has been found that the introduction of carbon nano-fillers could not only enhance the comprehensive performance of the polymer nanofiber membrane,but also endow the polymer nanofiber membrane with the good vapor sensing performance to organic vapors.The relationship between hierarchical structures and performance of the material is studied.The gas sensing effects and mechanisms are also explored.This paper mainly includes the following three parts1.At the beginning,a piece of polyurethane（PU）/polyethersulfone（PES）nanofiber mat with excellent flexibility was fabricated through electrospinning.Then,the blended PU/PES nanofiber mat was decorated with carbon nanotubes（CNTs）after experiencing ultrasonication.CNTs were uniformly distributed on the nanofiber surface,forming a perfect conductive network naturally.The prepared nanofiber composite membrane exhibited not only an ultralow percolation threshold of 0.056 vol%,but also a relatively high electrical conductivity of 2.8 S m^-1 at a low CNTs content of 0.85 vol%.In addition,the CNTs decoration enhanced the mechanical properties of the nanofiber membrane including tensile strength and Young’s modulus.The PU/PES/CNTs had a good sensing selectivity because of the different solubility of the solvent vapor to the polymer nanofiber.When it was exposed to the saturated acetone vapor,the response intensity（Ri）could reach⁸.8×102,while the response rate（RR）was only 9 s.The resistance of the sample could go back to its original value once the membrane composite was removed from the vapor to air,and the Ri could retain 90%after ten cyclic test,displaying a good sensing reproducibility.2.Flexible and super-hydrophobic nanofiber mats were fabricated by decorating the carbon nanofibers（CNFs）onto the blended polyurethane（PU）/polystyrene-block-poly（ethylene-co-butylene）-block-polystyrene（SEBS）nanofiber mat prepared through electrospinning.The introduction of CNFs with high degree of graphitization could not only greatly improve the mechanical and conductive properties of the nanofibrous membrane,but also endow the nanofibrous membrane with super-hydrophobicity.The super-hydrophobic PU/SEBS/CNFs nanofiber membrane showed corrosive solution（including salty,acid and alkali solution）repellent property and good stability in electrical conductivity and super-hydrophobicity.Moreover,the electrical conductivity of the nanofiber composite membrane kept stable even when the composite was exposed in a humid environment.It was discovered that the nanofiber composite mat could respond to both polar and non-polar vapors and display excellent repeatability in the sensing performance.3.Flexible polyurethane（PU）/polystyrene-block-poly（ethylene-co-butylene）-block-polystyrene（SEBS）nanofiber mat was firstly fabricated through electrospinning technique.Then,the acid treated carbon nanotubes（ACNTs）were dispersed and modified onto the surface of the PU/SEBS nanofiber by ultrasonication,followed by the hydrolysis of methyltrichlorosilane（MTS）on the ACNTs surface to obtain a conductive and super-hydrophobic nanofiber membrane.The nanostructured polysiloxane on the ACNTs surface derived from MTS hydrolysis enhanced the surface roughness of the materials and formed a hierarchical structure,thus endowing the polymer nanofiber with super-hydrophobicity with a maximum contact angle of 155°.In addition,the introduction of ACNTs and polysiloxane increased the mechanical strength of the nanofiber composite.The obtained PU/SEBS/ACNT/MTS with a unique porous structure and good flexibility could detect and distinguish different organic solvent vapors.As the nanofiber composite membrane was exposed to the environment containing acetone,toluene or heptane vapor,the corresponding response intensity（R₁）is about 2.8,1.4 and 1.1,respectively.