Direct Detection of the Chain Trajectory and Long-Range Correlation in Crystalline–Amorphous Polymer Networks by Single-Molecule Force Spectroscopy

Understanding the chain trajectory and long-range correlation in semicrystalline polymer networks is pivotal for elucidating the dynamic mechanism of plastic deformation and for guiding the rational design of high-performance polymeric materials. However, these features remain poorly resolved in condensed polymer systems due to the inherent limitations of conventional characterization techniques in temporal-spatial resolution. Utilizing single-molecule force spectroscopy, we demonstrate that mechanical forces universally activate the amorphous-chain translocation across the crystal lamella(e) within spherulites, independent of polymer categorization as αc-mobile or crystal-fixed systems. Through the real-time tracking of amorphous chain migration across adjacent lamellar crystals, we develop a novel methodology for mapping individual chain trajectories in three-dimensional spherulitic networks. Our findings reveal that the chain trajectory and long-range dynamics of a polymer chain are predominantly governed by monomer-specific surface energy. Quantitative analysis of chain mobility gradients demonstrates a hierarchy: polyethylene and isotactic polypropylene exhibit superior mobility; polycaprolactone displays intermediate behavior, while poly-l-lactic acid and polyamide 6 show restricted chain dynamics.