Permeability of Soft Particles at Electrical Fields.

The influence of the charge on the permeability of microgel particles is studied in the presence of electric fields. Electrophoresis experiments performed on pH-ionizable pNIPAM-AA microgels show that particles behave as permeable spheres when the network is ionized. However, they keep non-permeable in the absence of charge. The ionic nature of the network thus controls the permeability of the soft particles. A salt-dependent local viscosity explains these permeability changes. This is confirmed by NMR as alternative independent technique. Strongly hydrated counterions located around fixed charges on the network are considered responsible for the local viscosity variations.