Diffusional changes during the radical bulk polymerization of styrene with and without crosslinker were investigated. Full correlation fluorescence correlation spectroscopy (fcFCS) allowed for the simultaneous detection of rotational and translational diffusion of single fluorescent perylene diimide probes Small probes show a parallel decrease of both motions whereas for larger probes translation slows down faster than rotation The latter behavior contradicts the relationship between the Stokes Einstein and the Stokes-Einstein-Debye equation and is attributed to changes in the microviscosity and mesh size effects of the synthesized polymer chains The introduction of permanent cross-links results in additional restrictions for translational diffusion whereas rotation is not significantly affected up to high monomer-to-polymer conversions