Abstract
The pH value for different concentrations of aqueous Laponite® is varied through the range 0.445 to 13.450. The resulting crack patterns show four significant changes: (i)Near the acidic to basic crossover region pH 7: (a) The texture of the dried film changes from an opaque frosted look to a clear glassy appearance, (b) the pattern of cracks changes from an irregular fractal assembly of islands to straight- edged cracks forming a hierarchical tree pattern; (ii)At pH∼12.25 cracks are almost absent (iii) For a critical combination of concentration and pH value, lace-like crystallization patterns are observed on complete drying. SEM and EDAX studies on dry aggregates were also done. These experimental results are interpreted on the basis of the physico-chemical understanding of the structure of the Laponite® platelets, their mutual interactions and interaction with the pH of the surrounding medium.
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