Encai Ou

High concentration and stable few-layer graphene dispersions prepared by the exfoliation of graphite in different organic solvents

A series of stable graphene dispersions in different organic solvents were prepared by the liquid-phase exfoliation of microcrystalline graphite. The pristine graphite was heat-treated in N-methyl-2-pyrrolidone before it was exfoliated in solvents containing 0.1 mg mL−1 polyvinyl pyrrolidone (PVP). X-ray diffraction and scanning electron microscopy (SEM) results implied that the interlayer spacing of graphite increased after the heat treatment. The increased interlayer spacing makes it favorable for organic molecules to enter the lattice of graphite, and is helpful in the exfoliation of graphite for the production of graphene flakes. High resolution transmission electron microscopy (HRTEM) and Raman spectroscopy indicated that the resulting graphene flakes are high-quality products without any significant structural defects. Atomic force microscopy (AFM) showed that the graphene flakes consist of single-to-few layer graphene, and also demonstrated that the concentration of PVP is an essential factor in the deposition of graphene flakes onto a mica substrate. More importantly, the resulting graphene dispersions can be used to fabricate graphene films and disk arrays on quartz glass. Therefore, it is possible that the graphene dispersions in this study can be used for the preparation of large-area graphene films on different substrates.

Macroscopic, Free-Standing Ag-Reduced, Graphene Oxide Janus Films Prepared by Evaporation-Induced Self-Assembly

A facile, efficient, and unique self-assembly process for the preparation of the macroscopic, free-standing, Ag-reduced, graphene oxide (Ag-RGO) Janus films, which exhibit a unique asymmetry of their two surfaces with macroscopic dimensions, is presented. A novel strategy using an evaporation-induced, self-assembly (EISA) process is shown to be a powerful and flexible method for synthesizing well-defined Janus thin films.

ROMP of acetoxy-substituted dicyclopentadiene to a linear polymer with a high Tg

A polydicyclopentadiene derivative was obtained via ring-opening metathesis polymerization (ROMP) of acetoxy-substituted dicyclopentadiene (AcO-DCPD) using the Grubbs 1st generation catalyst. Analyses of the polymer microstructures indicate that polymers are linear. The glass transition temperatures (Tg) of the linear polymers range from 136 °C to 159 °C, which are much higher than that of linear polydicyclopentadiene.

Anionic polymerization of 1,3-pentadiene in toluene: homopolymer, alternating and block copolymers

The anionic polymerization of (E)-1,3-pentadiene (EP) and (Z)-1,3-pentadiene (ZP) was performed in aromatic solvent using n-butyllithium as initiator. In contrast to poly(ZP)s, the resulting poly(EP)s possessed the predicted molecular weights and narrow molecular weight distributions (Đ ≤ 1.15). However, THF as polar additive has proved its validity to reduce the molecular weight distribution of poly(ZP) from 1.55 to as low as 1.16. The 1H NMR and 13C NMR results indicated that both poly(EP) and poly(ZP) consist of 1,4-addition & 1,2-addition units, without 3,4-addition units. Moreover, a novel, well-defined styrene–pentadiene alternating copolymer has been synthesized in toluene via living anionic copolymerization and the NMR spectra demonstrated that the resulting copolymers obtained possess a strictly alternating structure and much narrower polydispersity (Đ ≤ 1.17). Finally, the living nature of the polymerization was also inspected via sequential copolymerization with methyl methacrylate (MMA) and 2-vinylpyridine (2VP) to yield well-controlled diblock copolymers (poly(EP)-b-poly(MMA) & poly(EP)-b-poly(2VP)).