PH dependent stability of aqueous suspensions of graphene with adsorbed weakly ionisable cationic polyelectrolyte

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Title: PH dependent stability of aqueous suspensions of graphene with adsorbed weakly ionisable cationic polyelectrolyte
Author(s): Griffith, Angus; Notley, Shannon M.
Abstract: Stable graphene suspensions were prepared through ultrasonic exfoliation followed by surface modification with the cationic polyelectrolyte poly(ethyleneimine) (PEI). The stability of the suspensions was found to be dependent upon the pH of the solution and the molecular weight of the PEI adsorbed. For the graphene sheets with adsorbed PEI with a molecular weigh of 600. Da, the particles were stabilised through an increased electrostatic repulsion at low pH inferred from in an increase in the measured zeta potential of the particles. However, the graphene with higher molecular weight PEI (70. kDa) was stable over a comparatively larger pH range through a combination of electrostatic repulsion at low pH and steric repulsion at elevated pH. Thus, solution conditions allowing the control of the colloidal sized graphene particles can be easily tuned through judicious management of solution conditions as well as polymer layer properties.
Publication type: Journal article
Source: Journal of Colloid and Interface Science, Vol. 369, no. 1 (Mar 2012), pp. 210-215
Publication year: 2012
FOR Code(s): 02 Physical Sciences; 03 Chemical Sciences; 09 Engineering
Keyword(s): Aqueous suspensions; Cationic polyelectrolyte; Colloid; Electrostatic repulsion; Fluid suspensions; Graphene sheets; Molecular weight; Particle size; pH range; pH-dependent; Polyelectrolytes; Polyethyleneimine; Polyethylenes; Polymer layers; Solution conditions; Sonication; Stability ratio; Stabilisation; Static electricity; Steric repulsions; Steric stabilisation; Ultrasound; Zeta potential
Publisher: Academic Press
ISSN: 0021-9797
Publisher URL: http://dx.doi.org/10.1016/j.jcis.2011.11.081
Additional information: Supported by the Australian Research Council.
Peer reviewed