STRUCTURE AND TRANSPORT OF LATEX MICROGELS IN AQUEOUS SUSPENSION

Cationic latex microgel particles were studied in dilute aqueous suspe nsions of varying ionic strengths. Static light scattering indicates a Gaussian distribution of polymer density over the length scales probe d. The measured radius of gyration is up to 50% larger than that obtai ned from TEM measurements of dried precursor particles. This radius of gyration is observed to be weak function of ionic strength. In contra st, dynamic light scattering measurements of the hydrodynamic radius s howed a strong dependence on ionic strength, giving a ratio of the gyr ation to hydrodynamic radii from 0.53 at low ionic strength to 0.76 at high ionic strength. We interpret these data as an increased friction on the microgel particles due to electroviscous effects. While we dra w a comparison of our measurements to existing theoretical results, th ere is at present no model to describe adequately these electroviscous effects for microgel particles.