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Electrospinning has emerged as a widely used and attractive technology for the production of long and continuous nanofibers with many desirable properties, such as large specific area-to-volume ratios, enhanced chemical reactivity, and a scalable and cost-effective manufacturing process. Depending on the tunable parameters of electrospinning, such as polymer type, solution concentration, solvent effect and electrospinning conditions, the structure and morphology of the nanofibers can be effectively controlled; this is one of the main advantages of electrospinning. With the development of electrospinning technology, many polymers and inorganic/polymer composites, such as PAN, PVA, PLLA, PVP, and PS, as well as their copolymers, have been fabricated and applied in various fields. Among polymer materials, polystyrene is a widely used polymer with the advantages of non-toxicity, odorlessness, excellent mechanical properties and stability. Scientists have used polystyrene in several applications, such as tissue engineering, filtration, and ion exchangers. Due to the hydrophobic properties of polystyrene, many superhydrophobic polystyrene membranes have been successfully prepared by electrospinning.Jiang et al [15] obtained polystyrene nanofiber membranes by electrospinning and demonstrated that the hydrophobicity of polystyrene can be improved by electrospinning. The contact angle increased to 140° compared to 95° for spin-coated polystyrene membrane. Because of the excellent superhydrophobic properties of electrospun polystyrene membranes, it can be hypothesized that nanofiber composite membranes can be prepared by combining polystyrene with other hydrophilic materials to achieve unidirectional water permeability. Although there have been many studies on unidirectional nanofiber membranes, few have used PS to prepare unidirectionally permeable composite membranes by electrospinning.PS composite nanofibers offer the possibility of preparing materials with unidirectional water permeability.
The main point of this paper
Polyethylene terephthalate (PET) is a very important material in apparel and non-fiber applications, known for its strength, chemical resistance, transparency, processability and dimensional stability. Although PET has low hydrophilicity, its hydrophilicity can be enhanced by hydrolysis with strong alkali to make it a hydrophilic material. Metal and metal oxide nanoparticles, such as AgNPs, CuNPs, AuNPs, TiO2, ZnO, MgO, and CuO, have been incorporated into electrospun membranes for air filtration, antibacterial, photocatalytic, and optical sensing applications. In particular, silver nanoparticles (AgNPs) have been widely used in the treatment of wounds and burns due to their broad-spectrum and efficient antimicrobial properties.
In this study, AgNPs-PS/PET nanofiber composite membranes with different AgNO3 additions were designed and prepared, and unidirectional water permeation was achieved by electrospinning. The morphology, structure and hydrophobicity of these composite membranes were discussed and the effects of viscosity and conductivity of AgNPs-PS electrospinning solution on membrane morphology were tested. In addition, the properties, processes and mechanisms of unidirectional water permeation of AgNPs-PS/PET membranes are demonstrated
AgNO3 addition:
The amount of AgNO3 added in the study was 0 wt%, 0.5 wt%, 1.0 wt% and 1.5 wt%, and 1.0 wt% was finally determined to be the optimal amount, which can realize the unidirectional water permeability function.
Characterization techniques:
The surface morphology and structure of AgNPs-PS/PET composite nanofibers were characterized using scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). the SEM images showed that the fibers of the composites were continuous and homogeneous during the electrospinning process
Wettability and unidirectional water penetration mechanism:
The contact angle (CA) was tested using a static contact angle meter to illustrate the wettability of the nanofiber composite film, and the unidirectional water penetration process was recorded. Meanwhile, the mechanism of unidirectional water penetration was analyzed
Viscosity and conductivity of electrospinning solution:
The effects of viscosity and conductivity of electrospinning solution on the membrane morphology were investigated, and these factors have an important influence on the final membrane morphology
The prepared AgNPs-PS/PET composite nanofiber membranes have the potential to be used in smart textiles, unidirectional water collection and wound dressing applications
In conclusion, hybrid nanofiber membranes with unidirectional water permeability were successfully prepared using PS-PET composites containing AgNPs prepared by electrospinning. From the AgNPs-PS side of the composite membranes, the morphology of all AgNO3-added composites was smooth with continuous and uniform nanofibers. The finest nanofibers with the largest average diameter were obtained when the addition of AgNO3 was 1.0 wt%, which was attributed to the effect of the addition of AgNO3 on the viscosity and electrical conductivity of the electrospinning solution. The successful introduction of Ag nanoparticles into the nanofiber composites was demonstrated by EDS and TEM results. By designing the structure of the composite film and testing the contact angle and penetration time, the AgNPs-PS/PET composites can be considered hydrophobic. The contact angle between the hydrophobic AgNPs-PS membrane and the hydrophilic PET membrane was greater than 90°. As a result, the hydrophobic-hydrophilic composite structure realized the unidirectional water permeation function (Fig. 2). The mechanism of unidirectional permeation was discussed accordingly. Furthermore, the prepared composites are expected to be used in wound dressings and self-cleaning devices. In addition, the prepared AgNPs-PS/PET nanofiber composite membranes with unidirectional permeation properties can be applied to wound dressings and self-cleaning devices.
