Structures and Segmental Dynamics in Single-Chain Polymer Nanoparticles-Based All-Polymer Nanocomposites

All-polymer nanocomposites are attracting dramatic attention due to their unique mechanical and viscoelastic properties. In this study, via multiscale solid-state nuclear magnetic resonance (NMR) methods, it is clearly revealed that a polystyrene (PS)-based single-chain polymer nanoparticle (SCNP) is in closer proximity with linear poly(vinyl methyl ether) (PVME) chains compared to linear PS chains, leading to dramatically different phase separation structures as demonstrated by 1H spin diffusion NMR experiments. High-resolution solid-state 1H NMR spectroscopy at ultrafast magic-angle-spinning (MAS) beyond 90 kHz directly reveals the subtle difference in proximity as well as the hydrogen bonding interactions between PVME and PS (or PS-SCNP) at a molecular level. Due to closer proximity between the PS-SCNP and PVME, the segmental dynamics of PVME is also slowed down by its hydrogen bonding interactions with PS-SCNP as revealed by variable-contact-time cross-polarization (CP) experiments. Particularly, 1H fast field cycling NMR experiments at variable temperatures clearly reveal the enhanced glassy and Rouse dynamic heterogeneity of PVME in the PS-SCNP/PVME blend. To the best of our knowledge, this is the first study to apply solid-state NMR spectroscopy to reveal the sophisticated interplay of structures and segmental dynamics in all-polymer nanocomposites at a molecular level, obtaining consistent results with molecular simulations, which could be helpful for the fundamental understanding of the unusual viscoelastic behaviors of all-polymer nanocomposites.