Probing the local dynamics in three-dimensional colloid-polymer assemblies using single particle tracking

We use single particle tracking (SPT) to understand the local environment around colloidal probe particles in colloid-polymer hybrid structures. These hybrids were prepared using ice templating. We have shown that variation in the crosslinking protocol for hybrid formation can dramatically alter their mechanical response¹. Elastic, compressible sponges or plastic monoliths can be prepared by varying crosslinking conditions. We use SPT to probe the microstructural differences that underlie the different mechanical response of elastic and plastic assemblies. We apply wavelet transforms to trajectories obtained from epifluorescence microscopy to eliminate error due to stage drift. This yields a spatial resolution of 2 nm in particle tracking. The mean squared displacements (MSD) showed subdiffusive behavior in both elastic and plastic scaffolds. However, the MSD and van Hove distribution for plastic scaffolds indicate larger spatial heterogeneity, in contrast to elastic sponges. This corresponds to heterogeneity in the local crosslinked polymer environment. We interpret this in terms of nonuniform distribution of crosslinks in plastic assemblies.
¹Langmuir 2016, 32, 11623−11630