(235a) Comparative Dynamics of Soft Colloidal Glass, Low Molecular Glass Former, and High Molecular Glass Former

After many years of modeling the liquid-to-solid transition for physical gels and soft glasses, the difference between these two material classes is still in dispute. This is where experimental rheology can help, since pronounced rheological differences between gels and glasses were found in the immediate approach of the liquid-to-solid transition from the liquid side.  Three very different glass formers of known linear viscoelasticity were chosen to exemplify the dynamics near the glass transition in contrast to gelation. The first system is a colloidal suspension of repulsive particles with increasing particle loading (collaboration with the Helmholtz Institute in Berlin, Germany; M. Ballauff and M. Siebenbuerger); the low molecular glass formers were studied in the group of G. McKenna, Texas Tech in Lubbock, Texas. The polymeric glass formers were polystyrene and polybutadiene. The alpha relaxation time of these systems follows the BSW relaxation pattern, but superposition master curves are not possible in a global way.