Developing multiphase polyurethanes (PUs) with loosely packed domains containing dynamic linkages and appropriately crystallized soft phases composed of polycaprolactone diol (PCL) segments is effective for the trade-off between toughness and self-healing. Here, we proposed a new strategy based on mixed dynamic hard segments to achieve the goal and improve self-healing behavior and mechanical performance. The designed polyurethanes comprise a microphase-separated structure with polycaprolactone diol as soft segments, which are facilitated to store entropy energy under strain. The aromatic disulfides together with aliphatic chain extenders were selected as hard segments to adjust the hierarchical structures, including microphase separation and crystallinity. The reversible hydrogen bonds and disulfide bonds distributed in the polymer network contribute to enhancing stretchability and self-healing performance. In this research, the robust polyurethanes with uniform microphase separation structures and insufficient crystallinity were designed by mixing a dynamic hard domain, which exhibits the potential application in the field of flexible conductors and synthetic muscles; the recovery efficiency at 90 °C is 93.8% and the ultimate stress/strain are 18.7 ± 0.2 MPa/2253 ± 149.2%. This work confirmed that the feasibility of synthetic PUs by changing the mole ratio of dual chain extenders simply, which is also expected to inspire the related fields of engineering, may require polymers with excellent self-healing efficiency and extraordinary robustness simultaneously.

We use a hybrid density functional approach to investigate the microstructure and self-assembly of inhomogeneous rigid rodlike chains between two neutral surfaces, i.e., two hard walls. In the calculation, the rodlike molecule is modeled as a rigid rod linearly connected by the tangent sphere beads. The hybrid method combines a single-chain Monte Carlo (MC) simulation for the ideal-gas part of Helmholtz energy and a DFT approach for the excess Helmholtz energy. The DFT approach includes a modified fundamental measure theory for the excluded-volume effect, the first order thermodynamics perturbation theory for chain connectivity, and the mean field approximation for the van der Waals attraction. We investigate the effect of the chain length (i.e., aspect ratio) of the rodlike molecule and the separation between two surfaces on the microstructure and self-assembly of inhomogeneous rigid rodlike chains. For the athermal systems, the rodlike chain fluids present a smaller partitioning coefficient compared to the flexible chain fluids. For the thermal systems, lamellar thin films formed by the rigid rodlike molecules perpendicular to the neutral surface are observed. The effects of the head-head interaction and the separation on the self-assembly of the rodlike chain fluids in the slit are investigated.

This work focuses on studying the excellent oxidation resistance performance and flexibility of electromagnetic shielding materials, greatly promoting the practical application in marine engineering, wearable field and electronic packaging field.