MICROGELS - COLLOIDAL MODELS FOR THE CROSS-LINKED STATE

This article describes the synthesis of various types of microgels wit h different cross-linking topologies. The swelling data of the standar d systems can be fitted with non-affine theories of rubber elasticity. Light scattering shows the existence of long-range swelling heterogen eities. The dynamic mechanical behaviour shows some peculiarities, e.g . small spherical microgels show viscous flow. Besides statistically c ross-linked systems, critically cross-linked as well as macroporous sy stems can be made. The critical systems exhibit a fractal structure sc aling which depends on synthetic conditions. This dependence agrees we ll with the different dynamic percolation theories. On the other hand, no clear relation between structure scaling and the observed dynamic behaviour can be found. A qualitative scheme which explains various ef fects observed during cross-linking of microgels is presented.