Stretching-induced restricted solvent dynamics in polymer organogels investigated using in-situ Rheo-NMR and X-ray scattering

While the mechanical properties of polymer gels are typically ascribed to the polymer network, the role of solvent dynamics—the majority component—remains elusive due to the lack of in-situ selective probing techniques. Here, by integrating operando Rheo-NMR with synchrotron radiation X-ray scattering (SRXS), we reveal a temperature-dependent coupling between macroscopic deformation and microscopic solvent confinement. Our results demonstrate a distinct bifurcation in behavior: at lower temperatures, the solvent dynamics remain relatively unperturbed as the network undergoes limited reorganization. However, at elevated temperatures ( T  ≥ 100 °C), a striking restriction of glycerol mobility is observed. In-situ SRXS uncovers the structural origin of this phenomenon: it stems from a competition between stretching-induced crystallite fragmentation and crystallization within the PVA network. At these elevated temperatures, crystallization is favored over fragmentation, resulting in a more constrained crystalline network environment that directly governs the solvent's rotational mobility. By establishing a direct correlation between stretching-induced structural evolution and solvent dynamics, this work offers a new perspective for designing high-performance soft materials through 'solvent engineering'.