Achieving enhanced dielectric performance of reduced graphene oxide/polymer composite by a green method with pH as a stimulus

Adjustable dielectric and bioactivity characteristics of chitosan-based composites via crosslinking approach and incorporation of graphene

This study explores the structural, electrical, dielectric, and bioactivity properties of chitosan (CS) composites incorporating graphene (G) nanoparticles. Characterization techniques, including Field Emission Scanning Electron Microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), dielectric spectroscopy, and in vitro testing in SBF, were employed to investigate the effects of G content and crosslinking. The XPS peak at 289.89 eV for CS-G10 indicates CC and CH bonds, suggesting significant interactions between chitosan's hydroxyl groups and graphene's carbon atoms, ensuring structural homogeneity. Dielectric constant (ε') gradually increased with G loading (0 %, 1 %, 5 %, and 10 %) for uncrosslinked composites, reaching 17.94, 18.92, 28.28, and 41.1, respectively. Crosslinked composites exhibited reduced ε' values (15.71, 15.42, 14.14, and 27.03) compared to non-crosslinked ones, with marginal increases post-percolation threshold (5 wt% G filling). XRD analysis revealed shifts in characteristic peaks of CS after SBF treatment, with new peaks at 28.9° and 48.5° indicating hydroxyapatite presence, confirming composite bioactivity. CS-G10/GA showed the highest bioactivity, suggesting promise for biomedical applications.

Bioinspired modified graphene oxide/polyurethane composites with rapid self-healing performance and excellent mechanical properties

Self-healing efficiency and mechanical strength are always a pair of mechanical contradictions of a polymer. Herein, a series of novel mussel-inspired modified graphene oxide/polyurethane composites were successfully fabricated via rational molecular design and introducing hyperbranched polymer-modified graphene oxide. The composites exhibit outstanding self-healing performances with a self-healing efficiency of 87.9%. Especially, their self-healing properties possess exceptional water-insensitivity, which presents a high self-healing efficiency of 92.5% under 60 °C water for 2 h and 74.6% under 25 °C water for 6 h. Furthermore, the tensile strength of the composites increased by 107.7% with a high strain of 2170%. In addition, the composites show a remarkable recovery capability of 76.3% and 83.7% under tensile and compression loading, respectively, after 20 cycles. This strategy shows prominent application potential in high-performance solid propellants, protective coating, electronic skin, soft sensors and other water-insensitive devices.

We successfully modified graphene oxide with amino-terminated hyperbranched polyamide(MGO), and obtained novel mussel-inspired MGO/polyurethane composites with outstanding self-healing and mechanical performances via rational molecular design.

Hyperbranched polyamide modified graphene oxide-reinforced polyurethane nanocomposites with enhanced mechanical properties

As is well known, it is difficult to simultaneously improve both the strength and elongation at break of polymers filled with nanomaterials. This work obtained high-performance composites with enhanced strength and elongation at break via cross-linking hydroxyl-terminated polybutadiene (HTPB) chains with hyperbranched-polyamide-modified graphene oxide (HGO), and the preparation, characterization, and mechanical properties of the composites serving as a composite solid-propellant binder have been described in detail. Compared with pure HTPB polyurethane (P-HTPB), the tensile strength and elastic modulus of the composite containing 0.1 wt% HGO (H-0.1/HTPB) increase by 57.8% and 65.3%, respectively. Notably, the elongation at break of the H-0.1/HTPB composite can reach up to 1292.6%, which is even higher than that of P-HTPB. Moreover, the capabilities of the composites to resist deformation have also been enhanced significantly. The glass transition temperatures of the composites are still extremely low (∼-73 °C), which is beneficial for their applications. It can be expected that this study can provide an effective fabrication approach and strategy for preparing high-performance polyurethane composites.