South China Advanced Institute for Soft Matter Science and Technology, Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices, South China University of Technology, Guangzhou 510640, China.
State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou 510640, China.
J Phys Chem Lett. 2022 Aug 4;13(30):7009-7015. doi: 10.1021/acs.jpclett.2c01817. Epub 2022 Jul 27.
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.
在亚纳观多面低聚倍半硅氧烷的组装体中，拓扑相互作用对其粘弹性有显著贡献，且具有广泛的可调性。组装分子设计为哑铃形、三角形和四面体形，在其本体中既没有长程有序，也没有超分子组装形成，表现出固有玻璃态特征。通过分子拓扑结构的剪裁，可以广泛调节其粘弹性，而三聚体和四聚体组装体在其玻璃化转变温度以上 80 K 时提供的弹性模量可与橡胶（约 0.5 MPa）相媲美。分子动力学研究揭示了由于簇组装体之间的拓扑破坏协同动力学而产生的拓扑限制，这最终导致了结构单元的典型笼状动力学和块状材料的弹性。进一步的宽带介电谱研究揭示了独特的分级弛豫动力学，为设计抗冲击材料提供了一种用于解耦力学强度和韧性的策略。
