Unexpected Elasticity in Assemblies of Glassy Supra‐Nanoparticle Clusters

Two-Dimensional Polymer Networks Locking on Inorganic Nanoparticles

Two-dimensional polymers (2DPs), single-layer networks of covalently linked monomers, show perspectives as membranes and in electronics. However, 2D polymerization of monomers in orthogonal directions limited the formation of 2DPs on nanoparticles (NPs) with high surface curvatures. Here we propose a high-curvature 2D polymerization to form a single-layer 2DP network as a non-contacting ligand on the surface of NPs for their stabilization and functionalization. The high-curvature 2D polymerization of amphiphilic Gemini monomers was conducted in situ on surfaces of NPs with various sizes, shapes, and materials, forming highly cross-linked 2DPs. Selective etching of core-shell NPs led to 2DPs as a non-contact ligand of yolk-shell structures with excellent shape retention and high NP-surface accessibility. In addition, by copolymerization, the 2DP ligands can covalently link to other functional molecules. This work promotes the development of 2DPs on NPs for their functional modification.

Topological Interaction among Molecular Cluster Assemblies Affords Tunable Viscoelasticity

In the assemblies of subnanoscale polyhedral oligomeric silsesquioxane, topological interaction makes the dominant contribution to their viscoelasticity with broad tunability. The assembly molecules are designed with dumbbell, triangular, and tetrahedral shapes, and they demonstrate an intrinsic glassy feature with neither long-range ordering nor supramolecular assembly formation in their bulk. Their viscoelasticity can be broadly tuned through the tailoring of molecular topologies, while the trimer and tetramer assemblies afford elastic moduli comparable to those of rubbers (∼0.5 MPa) even 80 K above their glass transition temperatures. Molecular dynamics studies reveal the topological constraints resulting from the topology-disrupted cooperative dynamics among the cluster assemblies, and this finally leads to the typical caging dynamics of the structural units and the elasticity of the bulk materials. Further broadband dielectric spectroscopy studies uncover the unique hierarchical relaxation dynamics, inspiring the strategy for the decoupling of mechanical strengths and toughness for the design of impact resistant materials.

Polymer Topology Reinforced Synergistic Interactions among Nanoscale Molecular Clusters for Impact Resistance with Facile Processability and Recoverability

The intrinsic conflicts between mechanical performances and processability are main challenges to develop cost-effective impact-resistant materials from polymers and their composites. Herein, polyhedral oligomeric silsesquioxanes (POSSs) are integrated as side chains to the polymer backbones. The one-dimension (1D) rigid topology imposes strong space confinements to realize synergistic interactions among POSS units, reinforcing the correlations among polymer chains. The afforded composites demonstrate unprecedented mechanical properties with ultra-stretchability, high rate-dependent strength, superior impact-resistant capacity as well as feasible processability/recoverability. The hierarchical structures of the hybrid polymers enable the co-existence of multiple dynamic relaxations that are responsible for fast energy dissipation and high mechanical strengths. The effective synergistic correlation strategy paves a new pathway for the design of advanced cluster-based materials.