Effect of Hydrophobic Moieties in Water-Soluble Polymers on Physical Exfoliation of Graphene

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• 作者：Hyeon Woo Shim ; Ki-Jin Ahn ; Kyungun Im ; Seonmyeong Noh ; Min-Sik Kim ; Younghee Lee ; Hojin Choi ; Hyeonseok Yoon
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：September 22, 2015
• 年：2015
• 卷：48
• 期：18
• 页码：6628-6637
• 全文大小：663K
• ISSN：1520-5835

文摘

Graphene is a fascinating material with unique properties, such as high mechanical strength and excellent electronic and thermal conductivities, as well as many other beneficial properties. Despite much recent effort, the facile synthesis and colloidal stabilization of graphene in aqueous solutions remains central to both academic research and practical applications. Here, we provide an in-depth insight into how the hydrophobic moieties of polymers affect the physical exfoliation of graphite into graphenes in aqueous solution. Four different polymers with graphene-like moieties, such as phenyl- and pyrenyl-functionalized side chains, were synthesized on the basis of the two water-soluble polymers poly(vinyl alcohol) (PVA) and dextran. Simply, sonication of graphite with the polymers in an aqueous solution produced stable graphene dispersions even after centrifugation. The ability of the polymers to exfoliate graphene sheets from the graphite was systematically investigated. Notably, 10 wt % phenyl-PVA led to the production of 46.7% bilayer and 26.7% 3- or 4-layer graphene flakes. An in-depth study into this and similar results was performed using density functional theory and MMFF94 computational tools, which led to better understanding of the interaction between graphene and the polymers in the solution. The polymers used can efficiently cleave graphite into graphene pieces without significant degradation of the sp² carbon bonding network and then stabilize them in the aqueous solution, in contrast with the so-called 鈥渞educed graphene oxide鈥? This approach is advantageous for the large-scale production of high-quality, few-layer graphene. Moreover, a judicious combination of the parent polymer backbone and the functional side chains might allow the control of the size and number of layers of the graphene flakes made in the aqueous solution. Lastly, graphene gels were directly prepared from the aqueous graphene/polymer solution; further, their potentials for two model applications, as a dye adsorbent and gel electrolyte, were demonstrated.