Glass, Gel, and Liquid Crystals: Arrested States of Graphene Oxide Aqueous Dispersions

Konkena, Bharathi and Vasudevan, Sukumaran (2014) Glass, Gel, and Liquid Crystals: Arrested States of Graphene Oxide Aqueous Dispersions. In: JOURNAL OF PHYSICAL CHEMISTRY C, 118 (37). pp. 21706-21713.

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Abstract

Colloidal systems with competing interactions are known to exhibit a range of dynamically arrested states because of the systems' inability to reach its underlying equilibrium state due to intrinsic frustration. Graphene oxide (GO) aqueous dispersions constitute a class of 2D-anisotropic colloids with competing interactions long-range electrostatic repulsion, originating from ionized groups located on the rim of the sheets, and weak dispersive attractive interactions originating from the unoxidized graphitic domains. We show here that aqueous dispersions of GO exhibit a range of arrested states, encompassing fluid, glass, and gels that coexist with liquid-crystalline order with increasing volume fraction. These states can be accessed by varying the relative magnitudes of the repulsive and attractive forces. This can be realized by changing the ionic strength of the medium. We observe at low salt concentrations, where long-range electrostatic repulsion dominates, the formation of a repulsive Wigner glass, while at high salt concentrations, when attractive forces dominate, the formation of gels exhibits a nematic to columnar liquid-crystalline transition. The present work highlights how the chemical structure of GO hydrophilic ionizable groups and hydrophobic graphitic domains coexisting on a single sheet gives rise to a rich and complex array of arrested states.

Item Type:	Journal Article
Publication:	JOURNAL OF PHYSICAL CHEMISTRY C
Publisher:	AMER CHEMICAL SOC
Additional Information:	Copy right for this article belongs to the AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	08 Nov 2014 05:05
Last Modified:	08 Nov 2014 05:05
URI:	http://eprints.iisc.ac.in/id/eprint/50160

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