Perpendicular Chain Orientation in Poly( para -Benzamide) Single-Crystal Nanowhiskers for Enhanced Dispersibility

Controlling nanoscale interfacial structure is critical for achieving uniform dispersion in polymer-filler systems. Here, we quantitatively elucidate the wetting behavior, dispersion stability, and interfacial thermodynamics of renewable-monomer-accessible poly(para-benzamide) (PBA) single-crystal nanowhiskers by employing a set of complementary nanointerface analysis techniques, namely, krypton adsorption (Kr-BET), inverse gas chromatography (iGC), and time-domain NMR (TD-NMR). The PBA nanowhiskers possess practical micrometer-scale dimensions yet exhibit an unusually high specific surface area (≈57 m2 g–1), evidencing a highly developed nanoscale surface texture. This feature originates from the crystallographically defined nanoscale interface generated by the perpendicular chain orientation, which exposes a high density of molecular steps and energetically active sites. In sharp contrast, size-matched poly(oxybenzoyl) (POB) whiskers and Kevlar cut fibers show extremely small accessible surface areas under identical Kr-BET conditions, reflecting aggregation and smooth chain-parallel morphologies. iGC analysis reveals that PBA exhibits a higher surface free energy and moderate energetic heterogeneity, including enhanced acid–base contributions, consistent with an energetically active nanointerface. TD-NMR further demonstrates that a larger fraction of solvent molecules undergoes restricted dynamics near the PBA surface, indicating a stronger solid–liquid affinity at the nanoscale interface. Notably, despite a smaller magnitude of negative zeta potential than that of POB, PBA shows superior dispersion stability, demonstrating that electrokinetic descriptors alone cannot predict the dispersion behavior. Collectively, these thermodynamic, relaxation, and electrokinetic results establish a molecular-orientation-driven pathway for engineering high-energy nanointerfaces, providing a quantitative design principle for achieving robust dispersion stability in solutions and polymer matrices.