Water-soluble graphene dispersion functionalized by Diels–Alder cycloaddition reaction

Facial fabrication of few-layer functionalized graphene with sole functional group through Diels-Alder reaction by ball milling

The widespread use of graphene as a next-generation material in various applications requires developing an environmentally friendly and efficient method for fabricating functionalized graphene. Chemically, graphene can be used as an electron donor or attractor. Here, graphite was successfully exfoliated, and an in situ Diels–Alder reaction (D–A) was carried out to fabricate functionalized graphene with sole functional groups via mechanochemical ball milling. The reactivities of graphene acting as a diene or a dienophile were investigated. Few-layer (≤2 layers) graphene specimens were obtained by wet ball milling, heating in a nitrogen atmosphere, and solvent ultrasonic treatment. The ball-milling method was more effective than heating in a nitrogen atmosphere, and the [2 + 4] D–A of graphene was more dominant than the [4 + 2] D–A in the ball-milling process. The surface tension of functionalized graphene decreased, which provided a theoretical basis for the dispersion and exfoliation of graphite in a suitable solvent. Functionalized graphene still had a high electrical conductivity, which has far-reaching significance for functionalized graphene to be applied in electronic semiconductors and related applications. Meanwhile, functionalized graphene was applied to polymer composite fibers, the tensile strength and the Young's modulus could reach 780 MPa and 19 GPa. The volume resistivity was two orders of magnitude lower than that of pure fiber. Thus, the use of ball milling to efficiently exfoliate and in situ functionalize graphite will help to develop a strategy that can be widely used to manufacture nanomaterials for various application fields.

The widespread use of graphene as a next-generation material in various applications requires developing an environmentally friendly and efficient method for fabricating functionalized graphene.

Fabrication and characterization of impact-resistant core-spun yarn fabrics with a hydroxylated fullerene-strengthened shear thickening fluid

Shear thickening fluid (STF) is investigated to strength soft armor; however, its impact resistance still does not meet practical needs. In this work, a small amount of hydroxylated fullerene (C₆₀) was mixed with STF to improve the thickening ratio. First, furfuryl alcohol (FA) was grafted onto C₆₀ through a Diels–Alder (D–A) reaction to improve the dispersity of C₆₀ in the STF. Sheath-core composite fibers (polyketone (PK) as the sheath and STF as the core) were then fabricated by coaxial electrospinning. Finally, composite fibers containing STF and C₆₀ were wrapped on the surface of aramid yarns to fabricate a core-spun yarn. Under impact, these core-spun yarns manifested the characteristics of aramid fibers and the thickening advantages of the STF, solving problems of the hygroscopicity, migration, and leakage of STF. In addition, the content of STF was also greatly increased. The spike punching resistance of the core-spun yarn fabric is about 2.8 times that of the aramid fabric (AF) under the same area density. Impact-resistant core-spun yarn fabrics could provide a new direction for the development of soft armor.

Shear thickening fluid (STF) is investigated to strength soft armor; however, its impact resistance still does not meet practical needs.

A versatile route to edge-specific modifications to pristine graphene by electrophilic aromatic substitution

Electrophilic aromatic substitution produces edge-specific modifications to CVD graphene and graphene nanoplatelets that are suitable for specific attachment of biomolecules.

Multiresponsive Shape-Stabilized Hexadecyl Acrylate-Grafted Graphene as a Phase Change Material with Enhanced Thermal and Electrical Conductivities

A phase change material (PCM) essentially making up hexadecyl acrylate-grafted graphene (HDA- g-GN) was fabricated via a solvent-free Diels-Alder (DA) reaction. The novel material exhibits multiresponsive, enhanced thermal and electrical conductivities and valid thermal enthalpy. In addition, the optimum DA reaction conditions were explored. A variety of characterization techniques were used to study the thermal, crystalline, and structural properties of HDA- g-GN. The melting and crystallizing enthalpies of HDA- g-GN were as high as 57 and 55 J/g, respectively. Furthermore, the melting and freezing points of HDA- g-GN were 29.5 and 32.7 °C, respectively. The thermal conductivity of HDA- g-GN reached 3.957 W/(m K), which is well above that of HDA itself and the previously reported PCMs. HDA- g-GN exhibited an excellent electric conductivity of 219 S/m. Compared to HDA, the crystalline activation energy of HDA- g-GN decreased from 397 to 278 kJ/mol (Kissinger model) and 373 to 259 kJ/mol (Ozawa model). Moreover, HDA- g-GN exhibited excellent thermal stability, shape stability, and thermal reliability. More importantly, HDA- g-GN can be employed to realize high-performance light-to-thermal and electron-to-thermal energy conversion and storage, which provides wide application prospects in energy-saving buildings, battery thermal management system, bioimaging, biomedical devices, as well as real-time and time-resolved applications.