  Synthetic hectorite clay Laponite RD/XLG is composed of disk-shaped
nanoparticles that acquire dissimilar charges when suspended in an aqueous
media. Owing to their property to spontaneously self-assemble, Laponite is used
as a rheology modifier in a variety of commercial water-based products.
Particularly, aqueous dispersion of Laponite undergoes liquid - to - solid
transition at about 1 volume % concentration. The evolution of the physical
properties as dispersion transforms to solid state is reminiscent of physical
aging in molecular as well as colloidal glasses. The corresponding soft glassy
dynamics of an aqueous Laponite dispersion, including the rheological behavior,
has been extensively studied in the literature. In this feature article we take
an overview of recent advances in understanding soft glassy dynamics and
various efforts taken to understand the peculiar rheological behaviors.
Furthermore, the continuously developing microstructure that is responsible for
eventual formation of soft solid state that supports its own weight against
gravity has also been a topic of intense debate and discussion. Particularly
extensive experimental and theoretical studies lead to two types of
microstructures for this system: an attractive gel-like or repulsive glass
like. We carefully examine and critically analyze the literature and propose a
state diagram that suggests aqueous Laponite dispersion to be present in an
attractive gel state.
