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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 32: Poster Session II

CPP 32.11: Poster

Tuesday, March 13, 2018, 14:00–16:00, Poster B

The Electrostatic Expansion of Ionic Microgels — Carlos G. Lopez, Thomas Lohmeier, •John E. Wong, and Walter Richtering — RWTH Aachen University

We report dynamic light scattering data for the hydrodynamic radius of a weakly charged PNIPAM based microgel as a function of temperature and added salt concentration.

Incorporation of 2% ionic co-monomers leads to an increase in the volume phase transition temperature of the microgel, which can be partially suppressed by addition of salt.

The charge induced swelling data are interpreted within the framework of the Flory-Rehner model, modified to include a Donnan term to account for the additional osmotic pressure arising from entropy of dissociated counterions. This model strongly under-predicts microgel swelling at all temperatures and added salt concentrations.

Our results suggest that repulsion between charged polymer segments plays a leading role in microgel expansion. Mean field theories for polyelectrolyte gels do not quantitatively capture this feature.