Inner Structure of Adsorbed Ionic Microgel Particles.

Microgel particles of cross-linkedpoly(NIPAM-co-acrylic acid) with different acrylicacid contents are investigatedin solution and in the adsorbed state. As a substrate, silicon witha poly(allylamine hydrochloride) (PAH) coating is used. The temperaturedependence of the deswelling of the microgel particles was probedwith atomic force microscopy (AFM). The inner structure of the adsorbedmicrogel particles was detected with grazing incidence small angleneutron scattering (GISANS). Small angle neutron scattering (SANS)on corresponding microgel suspensions was performed for comparison.Whereas the correlation length of the polymer network shows a divergencein the bulk samples, in the adsorbed microgel particles it remainsunchanged over the entire temperature range. In addition, GISANS indicateschanges in the particles along the surface normal. This suggests thatthe presence of a solid surface suppresses the divergence of internalfluctuations in the adsorbed microgels close to the volume phase transition. [ABSTRACT FROM AUTHOR]