Walter Richtering, Institute of Physical Chemistry, RWTH Aachen University, Germany

Unravelling the structure of complex microgels with scattering experiments

Microgels are macromolecular networks swollen by the solvent they are dissolved in. They are unique systems that are distinctly different from common colloids, such as, e.g., rigid nanoparticles, flexible macromolecules, micelles or vesicles. When swollen, they are soft and have a fuzzy surface with dangling chains and the presence of cross-links provides structural integrity - in contrast to linear and (hyper-) branched polymers. Due their properties, microgels can be used to tune the colloid-to-polymer transition.

We will discuss properties of microgels of different architecture as, e.g., ultra-low crosslinked, hollow and multi-shell, in aqueous solution. These microgels respond to various stimuli as, e.g. temperature and pH, and enable uptake and release applications. Furthermore, being soft allows microgels to respond to crowding in different ways, such as interpenetration, deswelling or faceting.

The structure of microgels and of complexes with guest species are investigated by means of scattering methods, especially exploiting the technique of contrast variation in small angle neutron scattering. The experimental results are be compared to computer simulations and to images obtained via super-resolved fluorescence microscopy. 

The lecture is part of the symposium Recent progress in small-angle scattering from soft matter and biological systems on the occasion of Professor Jan Skov Pedersen's 60th birthday.