Abstract:

Objective Traditional waterproof materials， such as coated fabrics or dense films， can effectively prevent the infiltration of external liquid water， reduce the risk of rainwater or pathogen transmission media entering， and minimize heat loss due to moisture wetting. However， their dense structure severely hinders the transfer of water vapor （sweat） produced by human metabolism to the outside. This leads to the accumulation of heat and moisture inside the clothing， causing discomfort such as stuffiness and clamminess. Prolonged wearing may even lead to skin problems or reduce the body's heat regulation efficiency. To address these issues， the development of functional membrane materials with both high waterproof and moisture-permeable properties has become a research focus in fields such as outdoor sportswear and medical protective clothing. The ideal waterproof and moisture-permeable membrane should facilitate the outward transmission of human sweat， prevent the inward infiltration of external moisture， and reduce body heat loss. This study aims to construct a Janus nanofiber membrane with asymmetric wettability through electrospinning technology， achieving a synergistic improvement in waterproofness and moisture-permeability.

Method Using electrospinning technology combined with asymmetric composite methods， a Janus nanofiber membrane was constructed. The waterproof and moisture-permeable membrane prepared by electrospinning features small fiber diameter， high porosity， good pore connectivity， controllable porous structure， easy surface modification， light weight， and flexibility. PVDF nanofiber membranes with different concentrations （10%， 12%， 14%） were prepared as the hydrophobic layer， followed by spinning TPU nanofiber membranes with different concentrations （26%， 28%， 30%） onto the PVDF fiber membrane as the hydrophilic layer， thus obtaining a PVDF/TPU composite Janus nanofiber membrane. By regulating the concentrations of the PVDF layer and the TPU layer， and characterizing and testing the morphology， surface wettability， hydrostatic pressure resistance， air permeability， and moisture permeability of the Janus nanofiber membrane， the optimal preparation process parameters were selected.

Results The PVDF/TPU composite Janus nanofiber membrane exhibits excellent waterproof and moisture-permeable properties. The composite membrane prepared with 12% PVDF and 30% TPU demonstrated the best overall performance. Under these conditions， the thickness difference between the PVDF layer and the TPU layer is small， and the interface between the two layers is tightly bonded without obvious delamination， ensuring the structural stability of the composite membrane. The 12%PVDF-30%TPU composite Janus nanofiber membrane shows good waterproof and moisture-permeable performance， with a water contact angle of 138.7°， indicating good hydrophobicity， a hydrostatic pressure resistance of 40.57 kPa； an air permeability of 17.8 mm/s； and a water vapor transmission rate of 7 335.7 g/（m²·d）， demonstrating favorable air and moisture permeability.

Conclusion The PVDF/TPU Janus nanofiber membrane， fabricated via electrospinning combined with an asymmetric composite strategy， successfully overcomes the limitation of traditional waterproof materials， which are typically "waterproof but not moisture-permeable." Leveraging the synergistic effect of the hydrophobic/hydrophilic bilayer structure， this membrane enables unidirectional moisture transport： it effectively blocks the ingress of external liquid water while efficiently expelling sweat vapor from the body surface. When the mass fractions of PVDF and TPU are 12% and 30%， respectively， the composite membrane exhibits excellent multifunctional protective properties， demonstrating promising application potential in fields that require h

Key words: Janus membrane, polyvinylidene fluoride, thermoplastic polyurethane, electrospinning, waterproof and moisture permeability, nanofiber membrane