Understanding the Polymer Chain Dynamics of Silicone Rubber Nanocomposites Adopting NMR Spectroscopy and AFM Phase Imaging

Understanding polymer chain dynamics is essential for tailoring the mechanical, thermal, and functional properties of polymer nanocomposites. In this study, we investigate the polymer chain dynamics of polydimethylsiloxane (PDMS) Boron Nitride (BN) nanocomposites using a combination of Solid-State Nuclear Magnetic Resonance (NMR) spectroscopy and Atomic Force Microscopy (AFM) phase imaging. Solid-state NMR spectroscopy, employing the Carr-Purcell-Meiboom-Gill (CPMG) echo sequence, provides quantitative insights into polymer chain dynamics and interfacial layer thickness by measuring transverse relaxation time (T2) correlating it to the wettability of the nanocomposites. Complementing the bulk dynamics captured by NMR, AFM phase imaging offers spatially resolved information on the viscoelastic properties and filler dispersion within the nanocomposites. Phase contrast in AFM identifies regions of constrained polymer mobility near nanofillers and highlights the heterogeneity in chain dynamics due to agglomeration or well-dispersed fillers. By correlating the bulk relaxation behavior from NMR with nanoscale heterogeneity observed in AFM phase images, we can establish a comprehensive understanding of how filler-polymer interactions influence chain mobility and macroscopic properties. Cross-linking density calculated for the composites provides a correlation with the elastic modulus which in turn provides an insight into the chain mobility.