Fabrication Of Reversible Photochromic Functional Nanofibrous Membranes With Water/Windproof And Breathable Performance

Waterproof and breathable fabric is a kind of functional fabric with outstanding waterproofness,moisture permeable properties,and ventilation properties,and the core functional layer of the breathable barrier fabrics is the waterproof and breathable membranes.This kind of membranes have a clearly visible system of holes as interconnected passage-ways and hydrophobic surface that enable them to discriminate between water droplets?diameter>100 um?and small molecular gases?diameter<1nm?in order to allow water vapor transforming from the human body to the outside while preventing the penetration of water.It is widely used in the production of protective clothing,medical applications,bioseparation,membrane distillation,moisture regulation of buildings,catalyst carriers,filtration and pharmaceutical.Electrostatic spinning technology can be used to prepare the fiber whose diameter ranges from several tens of nanometers to a few microns,through continuous accumulation,a fiber membrane with three-dimensional space network structure is formed.And its inner pore size is small and the porosity is high,which make the large droplets cannot penetrate and at the same time the water vapor can be transmitted outward through the transport channel due to the different temperatures between clothes inside and outside.Thermoplastic polyurethanes?TPU?as one hydrophobic/hydrophilic polymer with high mechanical strength,good elasticity,thermal stability,chemical resistance,and abrasive resistance have attracted great attention to prepare waterproof and moisture permeable membranes.Therefore,the electrospun TPU nanofibrous membranes have been greatly developed in waterproof and moisture permeable fabrics.However,the typical electrospun nanofibrous membranes usually appear white,which is the common color of polymers and mainly due to the physical phenomenon of light scattering.The phenomenon of photochromism is well known as the change of absorption spectrum caused by the molecular structure transformation under the irradiation of sunlight or ultraviolet light resulting in reversible changes in color,which has been widely used in decorative and protective packaging materials and other fields.Hence,considering the need for comfortability,aesthetic interest,and protection,it is necessary to develop a kind of multifunctional nanofibrous membrane,which not only possesses waterproof and moisture permeable properties,but also shows photochromic ability.And as far as we know,this material has rarely been reported up to now.In this work,to realize the intellectualization and multifunction of nanofibrous membranes,the TPU/PM composite waterproof and breathable nanofibrous membranes was fabricated through electrospinning using TPU and?photochromic microcapsule?PM as raw materials,and N,N-dimethylformamide?DMF?as solvent.Compared with the pristine TPU nanofibrous membranes,the composite TPU/PM membranes are endowed with reversible photochromic properties.In addition,the composite membranes not only exhibited a water contact angle of 137°and a milk contact angle of 130°,but also had integrated properties of modest water vapor transmittance rate of 1.9278×10⁴g m^-22 d^-1,high air permeability of 962mm s^-1,low waterproofness of 2.813 KPa,and comparable tensile strength of 12.08 MPa.Furthermore,the convenience and efficiency of this fabrication process will allow for large-scale production of the multifunctional nanofibrous membranes.