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

Abstract

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.