We want to study the osmotic deswelling behaviour in concentrated polystyrene microgel dispersions close to glass transition lines on adding varying amounts of linear polystyrene. Such dispersions show an unusually strong shift of the glass transition to higher volume fractions on polymer addition which has been tentatively attributed to particle shrinkage leading to a reduction of the effective volume fraction. We want to verify this proposition and to assess in how far osmotic deswelling is responsible for the unusual behaviour. At the same time we intend to check whether a deswelling theory derived from macrogel data can be applied to microgels as well. This requires the determination of the particle form factors of the microgels in concentrated microgel-polymer dispersions which is only possible by neutron scattering with contrast variation, i.e. on host-tracer mixtures in toluene/toluene-D8-mixtures. To achieve this required Q-range and resolution use of D11 is requested.