Gaigai Duan

Highly flexible and tough concentric triaxial polystyrene fibers.

A combination of appropriate reinforcing material and morphology led to the highly tough, flexible, and strong polystyrene fibers by electrospinning. Concentric fiber morphology with reinforcing elastomeric thermoplastic polyurethane (TPU) sandwiched between the two layers of polystyrene made by a special nozzle (triaxial) showed toughness of >270 J g(-1) and 300% elongation without any cracks in comparison to toughness of <0.5 J g(-1) and elongation at break of <5% of polystyrene single fibers. The concentric triaxial morphology showed great advantage in comparison to the coaxial structure. Toughness and elongation at break were 1376 and 628% higher, respectively, for triaxial morphology in comparison to the coaxial fibers because of the better interface from the sandwich structure.

Novel Layer-by-Layer Procedure for Making Nylon-6 Nanofiber Reinforced High Strength, Tough, and Transparent Thermoplastic Polyurethane Composites

We highlight a novel composite fabrication method based on solution casting, electrospinning, and film stacking for preparing highly transparent nylon-6 nanofiber reinforced thermoplastic polyurethane (TPU) composite films. The procedure is simple and can be extended to the other thermoplastics. The morphology of fiber/matrix interface and the properties of composite films were also investigated. The method led to a significant reinforcement in mechanical properties of TPU like tensile strength, E modulus, strain, and toughness just using very small amounts of nylon fibers (about 0.4-1.7 wt %; 150-300 nm diameter). The enhanced mechanical properties were achieved without sacrificing optical properties like transparency of TPU.

Spongy Gels by a Top-Down Approach from Polymer Fibrous Sponges

Abstract Ultralight cellular sponges offer a unique set of properties. We show here that solvent uptake by these sponges results in new gel‐like materials, which we term spongy gels. The appearance of the spongy gels is very similar to classic organogels. Usually, organogels are formed by a bottom‐up process. In contrast, the spongy gels are formed by a top‐down approach that offers numerous advantages for the design of their properties, reproducibility, and stability. The sponges themselves represent the scaffold of a gel that could be filled with a solvent, and thereby form a mechanically stable gel‐like material. The spongy gels are independent of a time‐consuming or otherwise demanding in situ scaffold formation. As solvent evaporation from gels is a concern for various applications, we also studied solvent evaporation of wetting and non‐wetting liquids dispersed in the sponge.

Ultralight open cell polymer sponges with advanced properties by PPX CVD coating

Ultralight polyacrylate sponges were prepared from dispersions of short electrospun polymer fibres by freeze drying and coated with poly(p-xylylene) (PPX) by chemical vapour deposition (CVD). The PPX coating of the sponges increased the compression strength, the water contact angle, and the solvent resistance significantly without significant alteration of the sponge morphology.

Electrospun nanofiber reinforced composites: a review

This paper provides a comprehensive overview on the properties of electrospun nanofibers and their application as reinforcements in composites. The paper first introduces the remarkable properties of electrospun nanofibers including high aspect ratio and molecular orientation, large specific surface area, small pore size, as well as excellent mechanical performance. Next the fabrication methods for the electrospun nanofiber reinforced composites are described. Then different kinds of electrospun nanofiber reinforced composites are discussed in terms of the classifications of electrospun nanofibers. After that, the influences of the mechanical performance of fibers, fiber diameter, fiber amount, fiber/matrix interfacial interaction and the distribution of fibers in the matrix on the reinforcement of composites are discussed. At the end, the possible future challenges and conclusions for electrospun nanofiber reinforced composites are highlighted.

Highly Efficient Reusable Sponge‐Type Catalyst Carriers Based on Short Electrospun Fibers

This study reports on gold nanoparticles (AuNPs) immobilized in a sponge made of short electrospun fibers (Au-sponge), which show surprisingly high reaction rates at extremely low gold amount. Au-sponges are made by freeze-drying of dispersions of short electrospun fibers with preimmobilization of AuNPs. The resulting Au-sponges show very low densities around 7 mg cm-3 corresponding to a pore volume of about 150 mL g-1 , but low surface area and very low amount of AuNPs in the range of 0.29-3.56 wt%. In general, catalysts with immobilized AuNPs show much low reaction rates compared to systems with dispersed AuNPs. By contrast, the Au-sponge catalyst with immobilized AuNPs is discerned here as an extremely efficient catalyst even superior to other systems with dispersed AuNPs. The fidelity of the Au-sponges after reactions is good enough for manifold use and thereby provides a sustainable catalyst design as well.

Exploration of Macroporous Polymeric Sponges As Drug Carriers

Achieving high drug loading capacity and controlling drug delivery are two main challenges related to drug carriers. In this study, polymeric macroporous sponges with very high pore volume and large porosity are introduced as a new-type of drug carrier. Due to the high pore volume (285 and 166 cm3/g for the sponges with densities of 3.5 and 6.0 mg/cm3, respectively), the sponges exhibit very high drug loading capacities with average values of 1870 ± 114 and 2697 ± 73 mg/g in the present study, which is much higher than the meso and microporous drug carriers (<1500 mg/g). In order to control the release profiles, an additional poly(p-xylylene) (PPX) coating was deposited by chemical vapor deposition on the drug loaded sponge. Consequently, Artemisone (ART) release in the aqueous medium could be retarded, depending on the density of the sponge and the thickness of the coating. In future, the new 3D polymeric sponges would be highly beneficial as drug carriers for the programmed release of drugs for treatment of chronic diseases.