Hierarchical Supramolecular Aggregation of Molecular Nanoparticles for Granular Materials with Ultra High-Speed Impact-Resistance.

The high-speed impact-resistanct materials are of great significance while their development is hindered by the intrinsic tradeoff between mechanical strength and energy dissipation capability. Herein, the new chemical system of molecular granular material (MGM) is developed for the design of impact-resistant materials from the supramolecular complexation of sub-nm molecular clusters (MCs) and hyper-branched polyelectrolytes. Their hierarchical aggregation provides the origin of the decoupling of mechanical strengths and structural relaxation dynamics.

Exploration of Molecular Nanoparticles as Soft Structural Materials and Their Structure-Property Relationship.

The search for alternative chemical systems other than polymers with chain topologies for soft structural materials raises general interests in fundamental materials and chemical sciences. It is also appealing from an engineering perspective for the urgent need to resolve the typical trade-offs of polymer systems. Herein, a subnanometer molecular cluster, polyhedral oligomeric silsesquioxanes, is assembled into molecular nanoparticles (MNPs) with star topology.

Unique Viscoelasticity and Hierarchical Relaxation Dynamics of Molecular Granular Materials.

Resulting from the dense packing of subnanometer molecular clusters, molecular granular materials (MGMs) are shown to maintain high elasticity far above their apparent glass transition temperature (*). However, our microscopic understanding of their structure-property relationship is still poor. Herein, 1 nm polyhedral oligomeric silsesquioxanes (POSSs) are appended to a backbone chain in a brush configuration with different flexible linker chains.

Functional Molecular Granular Materials: Advances and Perspectives.

Molecular granular materials (MGMs) are constructed with sub-nanoscale molecular clusters (MCs) as the building units and they have recently been observed to possess enriched functionalities distinct from granular materials of colloid nanoparticles. Herein, the birth and recent research advances in MGMs are summarized with the topics covering the precise synthesis of MC assemblies with target topologies, the hierarchical relaxation dynamics and tuneable viscoelasticity, impact-resistant capacity, and proton conductivity performance. The extremely small size of MC renders them two features: bulk diffusive dynamics with energy scale close to thermal fluctuation energy and the dominant volume fraction of surface structures.

Dimerization of sub-nanoscale molecular clusters affords broadly tuneable viscoelasticity above the glass transition temperature.

Materials with promising mechanical performance generally demonstrate requirements for the critical sizes of their key building units, entanglements and crystal grains. Herein, only with van der Waals interaction, viscoelasticity with broad tunability has been facilely achieved below the critical size limits: the dimers of ∼1 nm polyhedral oligomeric silsesquioxane (POSS) with < 4 kD and size < 5 nm, which demonstrate distinct material physics compared to that of polymer nanocomposites of POSS. The dimeric POSSs are confirmed by scattering and calorimetrical measurements to be intrinsic glassy materials with glass transition temperatures ( s) lower than room temperature.