Glassy Dynamics in Nanoconfinement as Revealed by 31P NMR

We investigated the glass former m-tricresyl-phosphate confined in different nanoporous silica matrices with defined pore radii from 2-150 nm. While applying different P-31 NMR techniques, we were able to detect the extremely stretched correlation functions extending over 7-8 decades in time and reflecting strong dynamic heterogeneities. The experimental results were explained by a topological model for which the broad distribution of correlation times G(ln tau) becomes inhomogeneous in space; that is, the "local" dynamics given by a correlation time tau(r) depend on the distance from the pore center. As tau(r) changes with temperature, we were able to reintroduce the idea of a dynamic correlation length.