Wenhui Xu

Polyimide complexes with high dielectric performance: toward polymer film capacitor applications

Novel polyimide–copper complexes (PICuCs) with a high dielectric constant of up to 133 were prepared by polymerization, complexation and imidization of a newly synthesized bipyridine-containing diamine monomer. The PICuCs showed high dielectric constant because of the enhanced electronic depolarization. Moreover, the PICuCs presented better mechanical and thermal properties than neat PI, which are promising materials for polymer film capacitors.

Ultralight electrospun cellulose sponge with super-high capacity on absorption of organic compounds

Three-dimensional, cost-effective, and renewable/recyclable absorbent materials with high capacities on absorption of organic compounds are urgently in demand. Herein, a facile while innovative approach is reported to develop ultralight electrospun cellulose sponge (UECS). The prepared UECS exhibits super-high absorption capacity (up to 232 times of its own weight) towards absorption of organic compounds due to high porosity (99.57%), low density (6.45mg/cm3), and hydrophobic surface feature (with water contact angle of 141.2°). Furthermore, the UECS is mechanically robust thus can be readily cut into different shapes; and it also possesses excellent stability against various organic compounds. Intriguingly, upon absorption of an organic compound, the shape-stable UECS organic gel can be formed. Hence, the developed UECS would be promising as environmental friendly absorbent on high-performance separation of organic compounds from aqueous systems; while the UECS organic gel could be utilized for the applications such as drug delivery and sensor.

Crown ether-containing polyimides with high dielectric constant

Polyimides (PIs) as a dielectric material have attracted much attention due to their good mechanical properties and thermal stability. However, the low dielectric constant of traditional PIs greatly restricts their applications in dielectric capacitors. Here we introduce crown ether groups into PI to increase the polarization of molecular chains. The resultant crown ether-containing PI films showed high dielectric constant and low dielectric loss, but without sacrificing the mechanical and thermal properties.

Scalable and Facile Preparation of Highly Stretchable Electrospun PEDOT:PSS@PU Fibrous Nonwovens toward Wearable Conductive Textile Applications

Flexible and stretchable conductive textiles are highly desired for potential applications in wearable electronics. This study demonstrates a scalable and facile preparation of all-organic nonwoven that is mechanically stretchable and electrically conductive. Polyurethane (PU) fibrous nonwoven is prepared via the electrospinning technique; in the following step, the electrospun PU nonwoven is dip-coated with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). This simple method enables convenient preparation of PEDOT:PSS@PU nonwovens with initial sheet resistance in the range of 35-240 Ω/sq (i.e., the electrical conductivity in the range of 30-200 S m-1) by varying the number of dip-coating times. The resistance change of the PEDOT:PSS@PU nonwoven under stretch is investigated. The PEDOT:PSS@PU nonwoven is first stretched and then released repeatedly under certain strain (denoted as prestretching strain); the resistance of PEDOT:PSS@PU nonwoven becomes constant after the irreversible change for the first 10 stretch-release cycles. Thereafter, the resistance of the nonwoven does not vary appreciably under stretch as long as the strain is within the prestretching strain. Therefore, the PEDOT:PSS@PU nonwoven can be used as a stretchable conductor within the prestretching strain. Circuits using sheet and twisted yarn of the nonwovens as electric conductors are demonstrated.

One-Step Preparation of Highly Hydrophobic and Oleophilic Melamine Sponges via Metal-Ion-Induced Wettability Transition

Hydrophobic and oleophilic absorbent materials have received wide attention in recent years for potential applications in pollutant removal from accidental spills of oil or organic chemicals. In this work, we report a metal-ion-induced hydrophobic melamine sponge (MII-HMS) prepared by a one-step solution immersion process. The commercial melamine sponge (intrinsically superhydrophilic with a water contact angle of ∼0°) is immersed in an aqueous solution of transition metal ions (e.g., FeCl3, Fe(NO3)3, Zn(NO3)2, Ni(NO3)2, and Co(NO3)2) for a short period, followed by drying. This simple process renders the transition of the superhydrophilic melamine sponge to become highly hydrophobic (a water contact angle of ∼130°). Results from X-ray photoelectron spectroscopy and infrared spectroscopy suggest that the unprecedented transition is likely due to the formation of metal complexes during immersion. The MII-HMS is also oleophilic, exhibiting excellent oil absorption capabilities, ∼71-157 times of its weight, for a wide range of oils and organic solvents. Our work offers a simple, scalable, and economical approach to fabricate highly efficient absorbent materials for potential applications in oil spill recovery and environmental remediation.