Zhu Baixu, Chen Jun, Li Ruipeng, Ren Jarett, Wang Yi, Zhong Yaxu, Liu Yang, Yasuhara Akira, Kakefuda Mayu, Aoyama Yoshitaka, Vo Thi, Ye Xingchen
Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.
National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY 11973, USA.
Sci Adv. 2025 Jul 18;11(29):eadw2740. doi: 10.1126/sciadv.adw2740.
Superlattices of polyhedral nanocrystals exhibit emergent properties defined by their structural arrangements, but native nanocrystal ligands often limit their programmability. Polymeric ligands address this limitation by enabling tunable nanocrystal softness through modifications of polymer molecular weight and grafting density. Here, we investigate phase transitions in polymer-grafted nanooctahedra by varying polymer length, nanocrystal size, truncation, and ligand density. In two-dimensional superlattices, longer polymers or smaller nanooctahedra induce a transition from orientationally ordered to hexagonal rotator lattices. In three-dimensional superlattices, increasing polymer length drives transitions from Minkowski to body-centered cubic and plastic hexagonal close-packed phases, while higher grafting densities further enable transitions to simple hexagonal phases. Polymer brush and thermodynamic perturbation theories, supported by Monte Carlo simulations, uncover the entropic and enthalpic forces that govern these transitions. This work highlights the versatility of polymer-grafted anisotropic nanocrystals as building blocks for designing hierarchical superstructures and metamaterials with customizable properties.
多面体纳米晶体的超晶格展现出由其结构排列所定义的涌现特性，但天然的纳米晶体配体常常限制了它们的可编程性。聚合物配体通过改变聚合物分子量和接枝密度来实现可调谐的纳米晶体柔软性，从而解决了这一限制。在此，我们通过改变聚合物长度、纳米八面体尺寸、截断方式和配体密度，研究了聚合物接枝纳米八面体中的相变。在二维超晶格中，较长的聚合物或较小的纳米八面体促使从取向有序晶格向六方旋转晶格转变。在三维超晶格中，增加聚合物长度会推动从闵可夫斯基相到体心立方相以及塑性六方密堆积相的转变，而更高的接枝密度则进一步促使向简单六方相转变。在蒙特卡罗模拟的支持下，聚合物刷和热力学微扰理论揭示了控制这些转变的熵力和焓力。这项工作突出了聚合物接枝各向异性纳米晶体作为构建具有可定制特性的分级超结构和超材料的多功能性。
