Generic Method to Create Segregated Structures toward Robust, Flexible, Highly Conductive Elastomer Composites

High-Performance Yet Sustainable Triboelectric Nanogenerator Based on Sulfur-Rich Polymer Composite with MXene Segregated Structure

State-of-the-art triboelectric nanogenerators (TENGs) typically employ fluoropolymers, highly negative chargeable materials in triboelectric series. However, many researchers nowadays are concerned about environmental pollution caused by poly-and per-fluoroalkyl substances (PFAS) due to their critical immunotoxicity as fluoropolymers are likely to release PFAS into the ecosystem during their life cycle. Herein, a sulfur-rich polymer (SRP)/MXene composite, offering high-performance yet sustainable TENG is developed. Value-addition of sulfur into SRP-based TENG has huge advantages since sulfur is abundant waste from petroleum refining and possesses the highest electron affinity (-200 kJ mol-1) among polymerizable atoms. MXene segregated structure is introduced into SRP to achieve homogeneous distribution without electrical percolation by utilizing below 0.5 wt% of MXene, resulting in a significantly enhanced dielectric constant without a drastic increase of dielectric loss. Due to homogeneous MXene distribution, SRP/MXene composite-based TENG demonstrates 2.9 times and 19.5 times enhances peak voltage and peak current compared to previous SRP-based TENGs. Additionally, it exhibits reusability without critical reduction of modulus and TENG performance due to dynamically exchangeable disulfide bonds. Finally, after the corona discharging and scaling-up process to a 4-inch wafer size, SRP/MXene composite-based TENG exhibits an 8.4 times improvement in peak power density, reaching 3.80 W m-2 compared to previous SRP-based TENGs.

A bio-based, self-healable, conductive rubber film with oxidized cellulose nanofiber segregated network

Rubber composites are indispensable in all areas of our daily lives. However, the formation of permanent crosslinked networks in rubber materials makes it difficult to recycle, resulting in a non-negligible waste of resources. In this paper, a vulcanization-free, fully bio-sourced rubber composite was prepared by using oxidized natural rubber (oNR) and oxidized cellulose nanofibers (TOCFs). TOCFs are selectively dispersed between the latex particles to form a segregated network. Meanwhile, the formation of hydrogen-bonding between oxygenated polar groups of oNR and abundant hydroxyl and carboxyl groups of TOCFs improves their interfacial interactions. This special structure promotes strain-induced crystallization (SIC) behavior of oNR matrix, giving its tensile strength up to 14.7 MPa. Furthermore, the oNR/TOCFs film shows excellent self-healing efficiency (96 %) at 40 °C for 5 h. The hygroscopicity of the TOCFs segregated network can turn the oNR/TOCFs film to be a conductive film by regulating the absorbed water content. The film has high conductivity (0.05 S/m) at a water content of 8.99 wt%, and the resistance change (RV/R0) can be varied between 1-5.9 × 10-6 at a water content range of 0-8.99 wt%, which makes it have potential for a wide range of humidity monitoring applications.

A Facile Method in Fabricating Flexible Conductive Composites with Large-Size Segregated Structures for Electromagnetic Interference Shielding

To resist the plastic deformation of polymer particles during hot press molding, high molecular weights, and moduli are required for composites with segregated structures, thus the prepared composites exhibit poor flexibility. Also, larger particle sizes can bring lower percolation thresholds while the ensuing greater deformation destroys the conductive network. Moreover, segregated composites still face preparation complexities. Herein, a facile method for developing flexible composites with large-size segregated structures is proposed. First, silver-coated polydopamine-modified reduced graphene oxide (Ag@PrGO), as conductive fillers, is prepared by electroless plating. Next, polydimethylsiloxane (PDMS)-coated polyolefin elastomer (POE) beads are put into a bag containing the fillers. After a simple shaking, the fillers are adhered to the POE surface as the cohesive property of cured PDMS. Finally, flexible composites with large-size segregated structures are obtained via hot pressing. Benefiting from the 2D structure of the Ag@PrGO and the ability to slip, the conductive networks possess adaptable deformability. The prepared composites exhibit excellent electrical conductivity (203.55 S cm-1) at filler volume fractions of 3.4 vol%. The EMI shielding effectiveness can reach 70 dB in the X-band at a thickness of 1.9 mm and remains stable after bending and rubbing damage. This work paves the way for constructing large-size segregated structures.

Morphology and Microwave-Absorbing Performances of Rubber Blends with Multi-Walled Carbon Nanotubes and Molybdenum Disulfide

This study details microwave-absorbing materials made of natural rubber/nitrile butadiene rubber (NR/NBR) blends with multi-walled carbon nanotubes (MWCNTs) and molybdenum disulfide (MoS₂). The mechanical blending method and the influences of fabrication on the morphology and microwave-absorbing performance of resulting compounds were logically investigated. It was found that interfacial differences between the fillers and matrix promote the formation of MWCNTs and MoS₂ networks in NR/NBR blends, thus improving microwave-absorbing performance. Compared with direct compounding, masterbatch-based two-step blending is more conducive to forming interpenetrating networks of MWCNTs/MoS₂, endowing the resulting composite with better microwave attenuation capacity. Composites with MWCNTs in NR and MoS₂ in NBR demonstrate the best microwave-absorbing performance, with a minimum reflection loss of -44.54 dB and an effective absorption bandwidth of 3.60 GHz. Exploring the relationship between morphology and electromagnetic loss behavior denotes that such improvement results from the selective distribution of dual fillers, inducing networking and multi-component-derived interfacial polarization enhancement.

Toward Mechanically Robust Crosslinked Elastomers through Phase Transfer Agent Tuning the Solubility of Zn2+ in the Organic Phase

Zinc oxide (ZnO), which is toxic to aquatic organisms, is widely used as an activator in the rubber industry. The reduction of ZnO content is one of the efficient ways to tackle ecological environment impacts induced by ZnO. However, the incompatibility between Zn2+ and organic matrix inhibits the solubility and activity of Zn2+ in the organic matrix, causing the heavy use of ZnO. This work develops a phase transfer agent with Zn2+-philic structure and oleophilic structure to increase the solubility of Zn2+ in the organic matrix. The phase transfer agent and Zn2+ form coordination interactions, while the hydrophobic chains of phase transfer agent and organic matrix form hydrophobic interactions. The above two interactions improve the solubility and activity of Zn2+ in the organic matrix, contributing to the formation of crosslinking network. Through the phase transfer agent strategy, we obtain the mechanically robust elastomers, and the samples with low ZnO content still maintain the superior properties. This work provides an efficient way to reduce ZnO content without sacrificing the performance of elastomers.