近日，日本东京大学的Hideyo Tsurusawa与Hajime Tanaka合作并取得一项新进展。经过不懈努力，他们探究了胶体凝胶中的分层无定形排序。相关研究成果已于2023年5月22日在国际知名学术期刊《自然—物理学》上发表。

据悉，在软物质和生物物质中，当相分离在没有结晶的情况下被动力学阻止时，就会形成无定形凝胶。虽然凝胶化的动力学阻止被认为与玻璃转变有关，但其微观基础尚不清楚。

为了解决这一问题，研究人员通过原位共聚焦显微镜观察的单粒子级动力学分析，对粘性胶体模型的凝胶化进行了实验研究。研究发现，在凝胶化过程中，单个胶体首先聚集成四面体，然后逐渐生长形成多个四面体簇。随后，五角双锥（pentagonal bipyramids）以五个四面体的组合形式出现，最终通过自催化二次生长形成介观范围的无定形有序结构并阻止动力学过程。这种分级排序主要由局部势能驱动，而非自由能。因此，相分离形成的凝胶和均质形成的玻璃之间的无定形排序和阻止机制在基本上存在差异。这些发现将深化我们对凝胶和玻璃这两种无定形固体的理解。

附：英文原文

Title: Hierarchical amorphous ordering in colloidal gelation

Author: Tsurusawa, Hideyo, Tanaka, Hajime

Issue&Volume: 2023-05-22

Abstract: Amorphous gels are formed in various soft matter and biomatter when phase separation is dynamically arrested without crystallization. The dynamic arrest in gelation has been attributed to glass transition, but a microscopic foundation is lacking. To address this issue, we experimentally study the gelation of a sticky colloid model using the single-particle-level dynamic analysis of in situ confocal microscopy observations. We show that, during gelation, individual colloids first aggregate into tetrahedra, which then grow to form poly-tetrahedral clusters. Subsequently, pentagonal bipyramids are formed as sets of five tetrahedra, and finally, these pentagonal bipyramids self-catalyse secondary growth to form medium-range amorphous order and arrest dynamics. This hierarchical ordering is primarily driven by local potential energy, not free energy. Thus, the amorphous ordering and arrest mechanism fundamentally differ between gels formed by phase separation and glasses formed homogeneously. These findings will deepen our understanding of two types of amorphous solid, namely, gel and glass.

DOI: 10.1038/s41567-023-02063-x

Source: https://www.nature.com/articles/s41567-023-02063-x