Designing Novel All-Polymer Nanocomposites with Pearl Necklace Chain Structure with High Strength, High Toughness, and Low Hysteresis

Service performance can be significantly improved by adding nanofillers into polymers. However, entropy effects and enthalpic interactions between traditional inorganic fillers and polymers impede the simultaneous attainment of high strength and strong toughness. Polymer-based soft nanoparticles (SNPs) have emerged as promising candidates for achieving a balance between strength and toughness. To fully harness the deformability potential of SNPs and achieve superior mechanical performance, the pearl necklace structure was designed by employing molecular dynamics simulation. Compared to traditional all-polymer nanocomposite system (S_T) composed of directly mixing polymer and SNPs, the SNPs in our novel system (S_N) exhibit better dispersion and compatibility. Primitive path analysis revealed that the pearl necklace chains endow a greater degree of penetration between SNPs and polymer. The confinement effects of cross-linking networks alter the diffusion dynamics of SNPs embedded within polymer chains. The restricted displacement fluctuation distance Formula Presented of SNPs in the S_N was obtained by the van Hove function G_s(r, Δt), a typical linear correlation between the Formula Presented and the mesh size of the polymer matrix cross-linked network ⟨L_c⟩. The distinctive structural and dynamic behaviors of the S_N are prominently reflected in the macroscopic mechanical properties. Stress decomposition analysis reveals that SNPs predominantly bear stress at low strain, whereas at high strain polymer dominates, akin to the reinforcement mechanism observed in dual polymer network of hydrogels. Moreover, SNPs within the S_N exhibit greater deformation and slower recovery rates compared to S_T, resulting in a 21.3% reduction in hysteresis loss. The toughness of the composites was evaluated through triaxial stretching. The S_N exhibits more uniform distribution of fibrils along the stretching direction, thereby enhancing crack resistance and increasing dissipated work by approximately 50% compared to S_T. In summary, this proposed novel pearl necklace structure opens a new avenue to balance the strength-toughness-hysteresis of polymer nanocomposites.