Structure and properties of chlorogenic acid-loaded polylactide fiber prepared by melt spinning.

Polylactide/chlorogenic acid (PLA/CGA) blends with different weight ratios were prepared by melt mixing, and corresponding PLA/CGA fibers were produced via a two-step melt spinning process. For PLA/CGA blends, CGA was distributed uniformly in the PLA matrix. The intermolecular interactions between CGA and PLA existed. The viscosity of PLA/CGA blends was much lower than that of neat PLA. With the increase of CGA content, the viscosity of PLA/CGA blends decreased. As the CGA content increased, the crystallinity of both PLA/CGA blends and fibers decreased. In addition, the tensile strength of PLA/CGA fibers was slightly lower than that of neat PLA fiber. For PLA/CGA fibers, the 6-fold drawn PLA/CGA fiber with 3 % CGA owned the highest tensile strength of 420 MPa. The ultraviolet (UV) resistance of PLA/CGA fibers were enhanced significantly by the introduction of CGA. When the CGA content was not <3 %, the UV transmittance of PLA/CGA fibers was <8 %. Moreover, PLA/CGA fibers exhibited good antioxidant properties. PLA/CGA fibers with 10 % CGA owned the highest antioxidant rate of >90 %. In addition, the 6-fold drawn PLA/CGA fiber with 10 % CGA presented excellent release performance with a 7-day cumulative CGA release rate of 19 %.

PVDF Nanofiber Modified with ZnO Nanowires/Polydopamine for the Treatment of Sewage Containing Heavy Metals, Organic Dyes, and Bacteria.

In various countries worldwide, the issue of wastewater contamination poses a significant threat due to its intricate composition of heavy metals, organic dyes, and microorganisms, thereby complicating the purification process. Consequently, researchers have expressed considerable interest in materials capable of eliminating organic, heavy metal, and microbial pollutants. This study focuses on the fabrication of a water purification membrane (PDA/ZnO-NWs/PVDF) with a hierarchical structure and the ability to remove multiple pollutants. The membrane was created by modifying poly(vinylidene fluoride) (PVDF) nanofiber with zinc oxide nanowires (ZnO-NWs) and reinforcing it with polydopamine (PDA). The experimental results demonstrate that the PDA/ZnO-NWs/PVDF membrane exhibits a range of functionalities, including long-lasting superhydrophilicity, Cu(II) adsorption, photocatalytic degradation, and antibacterial ability. The manipulation of the DA synthesis procedure allows for the adjustment of the wettability, adsorption, and photocatalytic and antibacterial activities of the PDA/ZnO-NWs/PVDF composite. According to the Langmuir isotherm, the maximum Cu(II) adsorption capacity of the PDA/ZnO-NWs/PVDF membrane is determined to be 65.75 mg/g, which is significantly higher (27.26 mg/g) than that of the ZnO-NWs/PVDF membrane (38.49 mg/g). The PDA/ZnO-NWs/PVDF composite exhibited a notable degradation capacity toward rhodamine B under natural sunlight, reaching a maximum of 5.97 mg/g. Additionally, the degradation rate achieved during daylight hours was as high as 90.42%. Furthermore, the antibacterial efficacy of the PDA/ZnO-NWs/PVDF composite against both Gram-positive and Gram-negative bacteria approached 100%. This work presents a promising approach for the treatment of wastewater containing various coexisting contaminants.

Smart photochromic materials based on polylactic acid.

The smart photochromic materials based on polylactic acid (PLA) were prepared by melt-blending and hot-pressing, in which photochromic microcapsules (PM) were used as a functional additive, and poly(vinyl acetate) (PVAc) was introduced into the photochromic PLA blends for the first time to improve their properties. The crystallization and melting behavior, morphology, and photochromic performance of PLA/PVAc/PM blends were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and spectrophotometer, respectively. The results showed that PVAc significantly improved the photochromic properties of PLA/PM blends. Under 30 s UV irradiation, the blends reached a value of ΔE that could be recognized in 3 s by human eyes. This discriminative ΔE value could be maintained for at least 3 min after removal from UV irradiation. Meanwhile, the blend had outstanding photochromic durability and recyclability. Compared to ΔE for 0.5 h of continuous light irradiation, ΔE for 8 h of continuous light irradiation decreased by only about 1, to 14.1. In 25 cycles of 3 s UV irradiation, the values of ΔE for the first and 25th irradiation were 11.4 and 11.6, respectively. The blend showed different photochromic responses to different light intensities. The ΔE values of 8.6, 14.6, 14.6, and 18.4 for irradiation at 600, 800, 1000, and 1200 W/m2 of solar intensity, respectively.

Mussel-Inspired Multifunctional Hydrogels with Adhesive, Self-Healing, Antioxidative, and Antibacterial Activity for Wound Healing.

Antibacterial hydrogel wound dressings with adhesive and antioxidant activity are desirable for treating skin injuries in clinical care. Hereby, a series of multifunctional hydrogel wound dressings with high adhesive, self-healing, antioxidant, and antibacterial activity were designed and fabricated using dopamine (DA) and quercetin (QT). The multifunctional hydrogels were constructed by the interpenetrated quaternized chitosan chain segments and polyacrylamide network. The catechol groups on DA, QT, and the quaternary ammonium groups in the hydrogel system endow hydrogels with high strength, excellent adhesion, and self-healing ability. The results confirmed the admirable hemocompatibility and remarkable antibacterial activity of the multifunction hydrogels against Staphylococcus aureus and Escherichia coli. Consequently, multifunction hydrogels with satisfactory adhesive and antibacterial activity are appropriate alternative materials in the fields of tissue adhesive and wound dressing applications.

Structure and properties of polylactic acid/butenediol vinyl alcohol copolymer blend fibers.

Polylactic acid/butenediol vinyl alcohol copolymer (PLA/BVOH) blends with different weight ratios were prepared by melt mixing. PLA and BVOH in PLA/BVOH blends were immiscible while the weak interaction between PLA and BVOH existed. The introduction of BVOH facilitated the crystallization of PLA. Moreover, the crystallization of PLA hindered the crystallization of BVOH. Due to introduction of BVOH, PLA/BVOH blends exhibited shear thinning characteristic except that PLA/BVOH blends with 5-10 % BVOH showed similar rheological property to neat PLA. With the increase of BVOH content, the contact angle of PLA/BVOH blends decreased from 79.75° to 67.33° at 120 s. The hydrophilicity of PLA/BVOH blends was improved. In addition, PLA/BVOH fibers with 5-40 % BVOH and PLA/BVOH/rutin fibers with 3 % rutin were manufactured by melt spinning. The effect of BVOH on the mechanical property of PLA/BVOH fibers was small. However, BVOH improved significantly the rutin release rate and antioxidant properties of PLA/BVOH/rutin fibers.

As Fiber Meets with AIE: Opening a Wonderland for Smart Flexible Materials.

Aggregation-induced emission luminogens (AIEgens) have recently been developed at a tremendous pace in the area of organic luminescent materials by virtue of their superior properties. However, the practical applications of AIEgens still face the challenge of transforming AIEgens from molecules into materials. Till now, many AIEgens have been integrated into fiber, endowing the fiber with prominent fluorescence and/or photosensitizing capacities. AIEgens and fiber complement each other for making progress in flexible smart materials, in which the utilization of AIEgens creates new application possibilities for fiber, and the fiber provides an excellent carrier for AIEgens towards realizing the conversion from molecule to materials and an ideal platform to research the aggregate state of AIEgens in mesoscale and macroscale. This review begins with a brief summary of the recent advances related to some typical AIEgens with various functions and the technology for the fabrication of AIEgen-functionalized fiber. The most representative applications are then highlighted by focusing on energy conversion, personal protective equipment, biomedical, sensor, and fluorescence-related fields. Finally, the challenges, opportunities, and tendencies in future development are discussed in detail. This review hopes to inspire innovation in AIEgens and fiber from the view of mesoscale and macroscale.

Quarternized chitosan/quercetin/polyacrylamide semi-interpenetrating network hydrogel with recoverability, toughness and antibacterial properties for wound healing.

Antibiotic abuse has posed enormous burdens on patients and healthcare systems. Hence, the design and development of non-antibiotic wound dressings to meet clinical demand are urgently desired. However, there remains one of the impediments to hydrogel wound dressings that integrated with good recoverability, toughness, and excellent antibacterial properties. Herein, a series of semi-interpenetrating network (semi-IPN) hydrogels with exceptional mechanical performance and remarkable antibacterial activity based on quaternized chitosan (QCS) and polyacrylamide (PAM) were developed using a one-pot method. Additionally, the antibacterial activity of semi-IPN hydrogel against S. aureus and E. coli was enhanced by integrating it with quercetin (QT). The semi-IPN hydrogels also exhibited high recoverability and toughness, outstanding liquid absorbability (the swelling ratio reached 565 ± 12 %), and a satisfying water vapor transmission rate. Moreover, the semi-IPN hydrogels presented ideal hemocompatibility and cytocompatibility. These high-elastic hydrogels are promising candidates for potential applications in wound dressing, tissue repair, chronic wound care, as well as other biomedical fields.

A Facile Strategy toward the Preparation of a High-Performance Polyamide TFC Membrane with a CA/PVDF Support Layer.

In this study, polyamide (PA) thin-film composite (TFC) nanofiltration membranes were fabricated via interfacial polymerization on cellulose acetate (CA)/poly(vinylidene fluoride) (PVDF) support layers. Several types of CA/PVDF supports were prepared via the phase inversion method. With increasing CA, the PVDF membrane surface pore size decreased and hydrophilicity increased. The effect of the support properties on the performance and formation mechanism of PA films was systematically investigated via an interfacial polymerization (IP) process. The permselectivity of the resulting TFC membranes was evaluated using a MgSO4 solution. The results show that the desired polyamide TFC membrane exhibited excellent water flux (6.56 L/(m2·h·bar)) and bivalent salt ion rejection (>97%). One aim of this study is to explore how the support of CA/PVDF influences the IP process and the performance of PA film.

ThePreparation of Electrospun PVDF/TBAC Multimorphology Nanofiber Membrane and Its Application in Direct Contact Membrane Distillation.

Microporous membrane with a hydrophobic surface, high porosity, and narrow pore size distribution is the ideal membrane distillation (MD) membrane. The electrospun membranes for MD are a new type and effective way to seawater desalination. Herein, a novel polyvinylidene fluoride (PVDF)/tetrabutylammonium chloride (TBAC) electrospun nanofiber membrane (ENMs) fabricated apply to for direct contact membrane distillation (DCMD). Combine with the spinning condition, the characteristic and content of TBAC significant effect on the multimorphology structure of nanofiber. Therefore, the porous structure and morphology of PVDF/TBAC ENMs can be well-designed by optimizing relative humidity and TBAC concentration in spinning process, three different structure nanofiber membranes are obtained. Lab-scale setup is used to test membrane separation performance. The result indicates that the ultrafine ENMs with 0.025 mol L-1 TBAC presented a steady water flux of about 20.6 L m-2 h-1 and a high-efficiency salt rejection rate of over 99%. PVDF/TBAC ENMs are expected to provide a solution for development of efficient water treatment membrane.

Preparation of Centella asiatica loaded gelatin/chitosan/nonwoven fabric composite hydrogel wound dressing with antibacterial property.

Antibiotics abuse and the emergence of massive drug-resistant bacteria have become the major obstacles in the medical system. Thus, designing an antibiotic-free wound dressing with antibacterial activity and decent biocompatibility is urgently desired. Herein, the sandwich-like composite hydrogel wound dressings were developed by intercalating nonwoven fabrics (NF) as the middle layer, gelatin and chitosan (Gel-CS) hydrogel loaded with Centella asiatica (CA) as the base materials. In addition, soaking strategy was employed to improve the mechanical properties of hydrogels. The hydrogels exhibited uniform microporous structure, stable mechanical property, high water absorbency, as well as water vapor transmission rate. After loading with CA, the composite wound dressing showed the sustained drug release properties in vitro and excellent antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The cytotoxicity results demonstrated that the composite hydrogels had good biocompatibility. This work indicates that the nonwoven composite hydrogels have broad application prospects in the field of medical care in the future.

Superelastic Polyimide Nanofiber-Based Aerogels Modified with Silicone Nanofilaments for Ultrafast Oil/Water Separation.

Nanofiber membranes via electrospinning with layered structures are frequently used for oil/water separation, thanks to their unique properties. However, challenges that involve nanofibrous membranes still remain, such as high energy consumption and unfavorable transport properties because of the densely compact structure. In this study, superelastic and robust nanofiber-based aerogels (NFAs) with a three-dimensional (3D) structure as well as tunable porosity were prepared using polyimide (PI) nanofibers via a freeze-drying process followed by the solvent-vapor treatment. The porous NFAs were further modified using trichloromethylsilane (TCMS) to generate silicone nanofilaments (SiNFs) on the surface of the PI nanofibers, which could enhance the hydrophobicity (water contact angle 151.7°) of the NFAs. The corresponding superhydrophobic NFAs exhibited ultralow density (<10.0 mg m-3), high porosity (>99.0%), and rapid recovery under 80% compression strain. SiNFs-coated NFAs (SiNFs/NFAs) could also collect a wide range of oily solvents with high absorption capacities up to 159 times to their own weight. Moreover, surfactant-stabilized water-in-oil emulsions could also be efficiently separated (up to 100%) under the driving force of gravity, making it a promising energy-efficient technology. Additionally, SiNFs/NFAs maintained high separation efficiency throughout five separation-recovery cycles, indicating the potential of SiNFs/NFAs in the field of oil/water separation, sewage treatment, as well as oily fume purification.

Solvent Vapor Strengthened Polyimide Nanofiber-Based Aerogels with High Resilience and Controllable Porous Structure.

Owing to the hierarchically three-dimensional (3D) network, ultralow density, and high porosity, nanofiber-based aerogels (NFAs) have drawn great attention recently. However, precise control of the porous structure and mechanical properties of NFAs, which have been proved to be extremely essential to the applications, still remains a major challenge. Herein, electrospun polyimide (PI) nanofibers were utilized as building blocks to construct NFAs through the solid-templating technique. The porous structure of PI nanofiber-based aerogels (PI-NFAs) could be adjusted by changing the processing parameters. By further welding the adjacent nanofibers at the contact sites with solvent vapor, high-resilience PI-NFAs were successfully prepared with comparable or higher recoverable, under compression, folding and torsion relative to other NFAs. The welded PI-NFAs showed ultralow density (minimum of 0.96 mg/cm3), high porosity (maximum of 99.93%), and tunable hierarchical structure. Therefore, this study brought a new perspective on the simple preparation of high-resilience nanofiber-based aerogels with tunable porous structures.

Fabrication of Multilayered Nanofiber Scaffolds with a Highly Aligned Nanofiber Yarn for Anisotropic Tissue Regeneration.

Nanofibrous scaffolds were widely studied to construct scaffold for various fields of tissue engineering due to their ability to mimic a native extracellular matrix (ECM). However, generally, an electrospun nanofiber exhibited a two-dimensional (2D) membrane form with a densely packed structure, which inhibited the formation of a bulk tissue in a three-dimensional (3D) structure. The appearance of a nanofiber yarn (NFY) made it possible to further process the electrospun nanofiber into the desired fabric for specific tissue regeneration. Here, poly(l-lactic acid) (PLLA) NFYs composed of a highly aligned nanofiber were prepared via a dual-nozzle electrospinning setup. Afterward, a noobing technique was applied to fabricate multilayered scaffolds with three orthogonal sets of PLLA NFYs, without interlacing them. Thus the constituent NFYs of the fabric were free of any crimp, apart from the binding yarn, which was used to maintain the integrity of the noobing scaffold. Remarkably, the highly aligned PLLA NFY expressed strengthened mechanical properties than that of a random film, which also promoted the cell adhesion on the NFY scaffold with unidirectional topography and less spreading bodies. In vitro experiments indicated that cells cultured on a noobing NFY scaffold showed a higher proliferation rate during long culture period. The controllable pore structure formed by the vertically arrayed NFY could allow the cell to penetrate through the thickness of the 3D scaffold, distributed uniformly in each layer. The topographic clues guided the orientation of H9C2 cells, forming tissues on different layers in two perpendicular directions. With NFY as the building blocks, noobing and/or 3D weaving methods could be applied in the fabrication of more complex 3D scaffolds applied in anisotropic tissues or organs regeneration.

Hierarchical Structured Polyimide-Silica Hybrid Nano/Microfiber Filters Welded by Solvent Vapor for Air Filtration.

Electrospun polymer membranes were considered to be promising materials for fine particulate matter (PM) filtration. However, the poor mechanical properties of the electrospun membrane restricted their application for pressure-driven air filtration. Herein, strength-enhanced electrospun polyimide (PI) membranes were demonstrated via a synergistic approach. Solvent-vapor treatment was utilized to introduce extra bonding at the cross points of PI nanofiber, while SiO2 nanoparticles (SiO2 NPs) were used to reinforce the body of nanofibers. The mechanical strength and filtration performance of hybrid membranes could be regulated by adjusting the quantity of SiO2 NPs. The tensile strength of the pure PI membrane was increased by 33% via adding 1.5% SiO2 NPs, which was further promoted by 70% after solvent-vapor treatment. With a slight reduction in pressure drop (6.5%), the filtration efficiency was not greatly suppressed by welding the SiO2 NP hybrid PI nanofibers. Moreover, the welded composite filter showed high particulate (0.3-1.0 µm) filtration efficiency (up to nearly 100%) and stable pressure drop throughout the 20 tested filtration cycles.

Mechanically-reinforced 3D scaffold constructed by silk nonwoven fabric and silk fibroin sponge.

Silk fibroin (SF) has made major contribution to the development of a rich variety of tissue-engineered scaffolds, mainly owing to its low cost, good biocompatibility, and proper biodegradability. However, scaffold of pure SF shows poor performance in terms of the mechanical strength, especially when they are constructed to a three-dimensional (3D), porous structure for bulk tissue regeneration. Herein, we report the fabrication of a typical class of 3D porous sponges made of SF, which are mechanically reinforced by integrating with a silk nonwoven fabric. It was found that the silk fibers in the fabric were closely bonded with SF inside the matrix sponge post freeze-drying, which significantly increased the compressive and tensile stress relative to the case of pure SF sponge. We then took fibroblasts (L929) as a model cell to investigate the 3D cell growth inside the scaffold. The cell viability, proliferation, and infiltration were noticeably improved when the silk nonwoven fabric was integrated into the SF sponge. Taken together, this class of mechanical-reinforced, 3D composite scaffolds hold great potential in the regeneration of bulk tissues and related applications.

Preparation of PI/PTFE-PAI Composite Nanofiber Aerogels with Hierarchical Structure and High-Filtration Efficiency.

Electrospun nanofiber, showing large specific area and high porosity, has attracted much attention across various fields, especially in the field of air filtration. The small diameter contributes to the construction of filters with high-filtration efficiency for fine particulate matter (PM), however, along with an increase in air resistance. Herein, composited nanofiber aerogels (NAs), a truly three-dimensional (3D) derivative of the densely compacted electrospun mat, were constructed with the blocks of polytetrafluoroethylene-polyamideimide (PTFE-PAI) composite nanofiber and polyimide (PI) nanofiber. PI/PTFE-PAI NAs with hierarchically porous architecture and excellent mechanical properties have been obtained by thermally induced crosslink bonding. Results indicated that sintering at 400 °C for 30 min could complete the decomposition of polyethylene (PEO) and imidization of polyamic acid (PAA) into PI, as well as generate sufficient mechanical bonding between adjacent nanofibers in the NAs without extra additive. The well-prepared PI/PTFE-PAI NAs could withstand high temperature up to 500 °C. In addition, the filtration tests illustrated that the composite NAs had an excellent performance in PM filtration. More importantly, the filtration behavior could be adjusted to meet the requirements of various applications. The excellent thermal stability and high-filtration efficiency indicated its great potential in the field of high-temperature air filtration.

Robust polyimide nano/microfibre aerogels welded by solvent-vapour for environmental applications.

Due to the high porosity, resilience and ultra-low density, polymer nanofibre-derived aerogels (NFAs) have been widely investigated in recent years. However, welding of the fibrous networks of NFAs, which has been proved extremely essential to their structural performance, still remains a major challenge. Herein, electrospun polyimide (PI) nano/microfibres were used as building blocks to construct hierarchically porous aerogels through a solid-templating technique. By further welding the adjacent nano/microfibres at their cross-points in a controllable fashion by solvent-vapour, super elasticity was achieved for the aerogels, with a recoverable ultimate strain of 80%. It is noteworthy that this process is free from cross-linking, heating and significant structure changing (i.e. chemical structure, crystallinity and fibrous network). Additionally, the porous structure of PI nano/microfibre aerogels (PI-N/MFAs) could be tuned by adjusting the organization of microfibres from a disordered/ordered cellular to a uniform structure. The as-obtained aerogels showed ultra-low density (4.81 mg cm-3), high porosity (99.66%), and comparable or higher recoverable compressive strain and stress relative to the other nanofibre-based aerogels. Furthermore, we showed the potential of such an aerogel for particle or aerosol filtration. PI nanofibre aerogels composite filters (PI-NFACFs) manifested excellent performance in PM2.0 filtration (99.6% filtration efficiency with 115 Pa pressure drop). Therefore, this study brought a new perspective on the simple preparation of nanofibre-based aerogels for air filtration.

Facile fabrication and characterization on alginate microfibres with grooved structure via microfluidic spinning.

Alginate microfibres were fabricated by a simple microfluidic spinning device consisting of a coaxial flow. The inner profile and spinnability of polymer were analysed by rheology study, including the analysis of viscosity, storage modulus and loss modulus. The effect of spinning parameters on the morphological structure of fibres was studied by SEM, while the crystal structure and chemical group were characterized by FTIR and XRD, respectively. Furthermore, the width and depth of grooves on the fibres was investigated by AFM image analysis and the formation mechanism of grooves was finally analysed. It was illustrated that the fibre diameter increased with an increase in the core flow rate, whereas on the contrary of sheath flow rate. Fibre diameter exhibited an increasing tendency as the concentration of alginate solution increased, and the minimum spinning concentration of alginate solution was 1% with the finest diameter being around 25 µm. Importantly, the grooved structure was obtained by adjusting the concentration of solutions and flow rates, the depth of groove increased from 278.37 ± 2.23 µm to 727.52 ± 3.52 µm as the concentration varied from 1 to 2%. Alginate fibres, with topological structure, are candidates for wound dressing or the engineering tissue scaffolds.

Morphology and crystallization behavior of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polyhedral oligomeric silsesquioxane hybrids.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polyhedral oligomeric silsesquioxane (PHBV/POSS) hybrids with different POSS contents of 5, 10, 15, 20, 25 and 30 wt% were prepared by solution casting. The composition, crystallization and melting behavior, crystal structure, spherulite morphology, surface morphology, and tensile properties of PHBV/POSS hybrids were characterized by EDS, DSC, FTIR, XRD, HSPOM, AFM and a tensile testing machine. The results showed that POSS was well dispersed in the PHBV matrix. PHBV and POSS crystals coexisted in the hybrids. The crystallinity of pure PHBV was larger than that of PHBV/POSS hybrids. POSS restricted the crystallization of PHBV in PHBV/POSS hybrids. With the increase of POSS content, the crystallinity of PHBV/POSS hybrids decreased from 56.8 (pure PHBV) to 33.6% (PHBV/POSS hybrid with 30 wt%). However, the introduction of POSS did not affect the spherulite morphology of PHBV. The Avrami equation was used to describe the isothermal crystallization kinetics of PHBV/POSS hybrids. The results showed that as the crystallization temperature increased, the crystallization rate became slow. In addition, POSS can improve the tensile properties of PHBV.

A review: the effect of the microporous support during interfacial polymerization on the morphology and performances of a thin film composite membrane for liquid purification.

The thin film composite (TFC) membrane prepared by interfacial polymerization (IP) on porous supports is currently one of the most efficient technologies for brackish water purification and seawater desalination, including reverse osmosis (RO), forward osmosis (FO), and nanofiltration (NF). Over the past decades, there have been intensive and continuous efforts in research of polyamide layers, while there is little information in the literature about the impact that physical-chemical properties and structure of support membranes have on the formation of composite membranes. This paper reviews the recent research progress of the supporting membrane, comprehensively summarizes the support role in polyamide formation, and provides good insight into TFC membrane research and development. In addition, we discuss several types of polymer supporting membranes and related modification methods to explore the appropriate supporting membrane for enhancing TFC membrane performance and extending the applications in the future.