Properties of ionic microgels and interparticle interaction

In Tab. 14.2 some of the prepared microgels are characterized in terms of dimension and molar mass. The measured Rg/Rh values lie in the range 0.7 Rg/R/, 1 which indicates a spherical shape of the microgels. 

In Fig. 14.6 the measured apparent particle radii are shown as function of the ionic strength. The ionic strength dependence does not clearly emerge from the plot because above a concentration of 0.01 m salt the particles start to aggregate and eventually precipitate, and below 0.001 m salt electrostatic effects prohibit a proper size evaluation, as will be discussed in detail below. It appears, however, that due to the high cross-linking density the particles 

Approximate molar masses measured in methylformamide solution with an estimated dn/dc = 0.1 cm /g 

Strong swelling. This point is still under investigation along with peculiar interparticle, electrostatic interaction effects affecting the solution properties of the micronetworks, as already discussed above. 

These experiments support the recent claims [7] that the conformational change of the polyions is not responsible for the anomalous viscosity behaviour. The observed maximum in the reduced viscosity is most likely caused by a maximum in the electrostatic interaction energy. Light scattering experiments at concentrations larger than the concentration of the highest viscosity are currently performed and will provide a more detailed insight into such complex electrostatic phenomena. 

---