  Hypothesis: Aging in colloidal suspensions manifests as a reduction in
kinetic freedom of the colloids. In aqueous suspensions of charged colloids,
the role of inter-particle electrostatics interactions on the aging dynamics is
well debated. Despite water being the dispersion medium, the influence of water
structure on the physicochemical properties of aging colloids has never been
considered before. Laponite, a model hectorite clay, could be used to evaluate
the relative contributions of medium structure and electrostatics in
determining the physicochemical properties of aging colloidal suspensions.
  Experiments: The structure of the dispersion medium is modified either by
incorporating uncharged/charged kosmotropic (structure-inducing) or chaotropic
(structure-disrupting) molecules or by changing suspension temperature. A new
protocol, wherein the medium is heated before adding clay particles, is also
introduced to evaluate the effects of hydrogen bond disruptions on suspension
aging. Dynamic light scattering, rheological measurements and particle-scale
imaging are employed to evaluate the physicochemical properties of the
suspensions.
  Findings: A strong influence of medium structure is evident when
inter-particle electrostatic interactions are weak. Enhancement and disruption
of hydrogen bonds in the medium are, respectively, strongly correlated with
acceleration and delay of suspension aging dynamics. The physicochemical
properties of charged clay colloidal suspensions are therefore controlled by
altering hydrogen bonding in the dispersion medium.
