Nanoparticle Diffusion in Polymer Nanocomposite Melts

Nanoparticle (NP) diffusion in crowded polymer nanocomposites (PNCs) is largely unexplored due to experimental limitations and is a critical analog to biological systems. We recently demonstrated the use of time-of-flight secondary ion mass spectroscopy (ToF-SIMS) to measure NP or polymer diffusion into neat polymer melts. Here, we investigate NP diffusion into crowded poly(2-vinylpyridine) (P2VP) nanocomposite melts. NP diffusion is measured across micron-length scales across a range of NP loadings to explore the effect of interparticle distances. Specifically, we measure the diffusion coefficients of alumina NPs (diameter 13 nm) into nanocomposite with silica NPs (diameter 52 nm). We control the interparticle distance by varying the concentration of the silica NPs and separately detect the concentration profile of the alumina NPs using the elemental-specific capabilities of ToF-SIMS. Surprisingly, the alumina NP diffusion coefficients are depressed relative to diffusing into neat P2VP, even at interparticle distances substantially larger than the alumina NPs. This work quantifies the effect of particle loading on NP diffusion in attractive PNC and provides insight into diffusion in crowded PNC systems.