Monolithic Crystalline Swelling of Graphite Oxide: A Bridge to Ultralarge Graphene Oxide with High Scalability

The large-scale preparation of ultralarge graphene oxide (ULGO) is urgently needed for developing advanced devices and high-performance nanocomposites. However, it is extremely difficult to produce ULGO in an industrially viable, high-efficiency manner because of the inevitable sheet fragmentation and significant gelation behavior occurred in existing methods. We propose a stationary oxidation-monolithic crystalline swelling strategy that can completely convert graphite to ULGO. This new stationary oxidation method minimizes the sheet fracture and prevents the exfoliation of oxidized layers without sacrificing the oxidation rate, resulting in oxidized flakes with high crystalline and lateral sizes the same as raw graphite. The oxidized graphite flakes undergo a monolithic crystalline swelling during the purification, leading to the formation of a three-dimensional ordered structure without peeling. This enables graphite oxide to be purified by spontaneous sedimentation within 1 h as gelation is avoided and to be exfoliated exhaustively into single-layered ULGO sheets through mild mechanical shaking, with an average size of 108 μm and the largest size of 256 μm. These ULGO sheets can form liquid crystals at a record dispersion concentration (as low as 0.2 mg/mL). The ULGO papers show outstanding mechanical properties and electrical conductivities (after HI reduction) that outperform the reported results

Interlayer Polymerization in Chemically Expanded Graphite for Preparation of Highly Conductive, Mechanically Strong Polymer Composites

The large-scale application of graphene–polymer composites needs a simple, low-cost method that simplifies the preparation process of graphene and optimizes the structure and properties of composites. We propose the first interlayer polymerization in chemically expanded graphite (CEG) with large specific surface areas, which allows CEG to be spontaneously exfoliated into single- and few-layer graphene in poly­(methyl methacrylate) (PMMA). Our results demonstrate that besides weakened interlayer interactions, the surface wettability of CEG to monomers is a critical prerequisite for the desired graphene exfoliation, dispersion, and performance optimization of composites. The slightly oxidized CEG (LCEG) improved to some extent the affinity for the monomer but is not sufficient to achieve complete exfoliation of LCEG, so that the resulting composites reveal the mechanical and electrical properties that are far poorer than those of the surface-modified LCEG-based composites. The latter not only exhibit a significantly enhanced elastic modulus, increased as much as 3-fold relative to that of the neat PMMA, but also show an extremely high electrical conductivity, of >1700 S/m. Such a novel interlayer polymerization approach is expected to accelerate the use of industrial applications of a wide range of graphene-based composites

Polymer-Grafted Nanoparticles with Precisely Controlled Structures

Polymer-tethered nanoparticles with different geometric shapes are very useful fillers of polymer nanocomposites. Herein, a universal approach for the fabrication of such nanoparticles with precisely controlled shape and composition is reported. By microphase separation of poly­(3-(triethoxysilyl)­propyl methacrylate)-<i>block</i>-polystyrene (PTEPM-<i>b</i>-PS) in the presence of oligomers, o-TEPM (oT) and/or o-S (oS), followed by cross-linking and dispersion in PS solvent, precisely tailored PS-grafted nanoparticles were prepared. These particles include those with varied shapes but identical PS shells, particles with varied core sizes but the same PS shell, and particles with fixed shapes but varied PS shells. These particles are ideal model nanofillers to study the dynamics and reinforced mechanism of polymer nanocomposites