PUB - Publikationen an der Universität Bielefeld

The structural and dynamic properties of thermosensitive neutral and partially charged colloidal microgels of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM/AAc) have been investigated by neutron and light scattering techniques. Introduction of cross-linker induces topological constraints into the polymer network, and hence reduces the swelling capability of the particles as expressed in the variation of their hydrodynamic radii. Small-angle neutron scattering experiments reveal that below the transition temperature the inhomogeneous structure of the microgel consists of local solid-like frozen regions and solution-like regions where the polymer chain behaves as in semidilute polymer solution. The temperature-induced collapse leads to a strongly segregated micro-phase separated particle. The swelling of charged microgels is determined by their charge density, controlled through the amount of acrylic acid comonomer, the pH, and the salt concentration.