Single-molecule conformations probe free volume in polymers.

In this communication, we showed that the conformational dynamics of the tetraphenoxy-perylenetetracarboxy diimide single dye molecule embedded in different polymer matrixes allows a direct visualization of the local free volume. By monitoring the fluorescence lifetime of the dye molecule in time and at different locations in the matrix, different lifetimes were observed. Attributed to two distinct stable conformations of the dye molecule, the lifetime variations permitted characterization of the spatial distribution and temporal dynamics of free volume.