Aggregation of laponite in the presence of magnesium ions and polyacrylic acid

The average mass and size characteristics of ageing laponite/MgCl2 and lapo nite/MgCl2/polyacrylic acid were determined in aqueous dispersions at pH 10 using a Coulter counter and laser diffractometry methods. Comparison betwe en mass and size characteristics showed the two systems to temporarily acqu ire a structure where particles are more densely packed. The relatively hig her packing observed for laponite/polymer was attributed to conformational changes of the polymer adsorbed on neighbouring surfaces. Analysis of the r educed mass and size distribution functions confirmed the self-similarity o f the distributions. The reduced mass frequency continuously decreased, whi le the reduced size frequency showed a linear decrease combined with bell-s haped populations. The volume packing observed for the laponite/polymer was attributed to a typical class of aggregates of large size, which was prese nt at the maximal concentration in the bell-shaped distribution.