Morphologically Tunable Square and Rectangular Nanosheets of a Simple Conjugated Homopolymer by Changing Solvents

Two-dimensional (2D) polymer nanosheets have been attracting immense attention owing to their potential applications in optical devices, membranes, and catalysis. However, creating uniform monolayered 2D nanosheets through polymer self-assembly is very challenging, especially when using homopolymers. In this work, we designed a new crystalline polyacetylene that contains fluorenes and triisopropylsilyl side chains, which could self-assemble into sharp-edged 5-nm-thick square nanosheets with a narrow length dispersity of 1.01, by simple heating and aging in dichloromethane (DCM). Interestingly, the addition of tetrahydrofuran (THF) or chloroform to the heated polymer solution in DCM changed the morphology from square to rectangle. The aspect ratios increased linearly, from 1.0 to 10.6, according to the amount of THF or chloroform added, while maintaining narrow length dispersities less than 1.06. These unique fluorescent semiconducting nanosheets with tunable shapes exhibit high potential for optoelectronic applications.二维（2D）聚合物纳米片因其在光学器件、分离膜及催化领域的潜在应用价值而受到广泛关注。然而，通过聚合物自组装制备均匀的单层二维纳米片极具挑战，对于均聚物体系而言尤为如此。本研究设计了一种含有芴基与三异丙基硅基侧链的新型结晶性聚乙炔，通过在二氯甲烷（DCM）中简单加热并陈化，该聚合物可自组装得到边缘规整、厚度为5 nm的正方形纳米片，其长度分散度仅为1.01，分布极窄。值得注意的是，向该二氯甲烷中的加热聚合物溶液中加入四氢呋喃（THF）或氯仿（chloroform）时，纳米片的形貌会从正方形转变为矩形。随着所加入四氢呋喃或氯仿的用量增加，纳米片的长径比从1.0线性增长至10.6，且始终保持长度分散度低于1.06，分布依旧狭窄。这类形貌可调的独特荧光半导体纳米片在光电应用领域展现出极高的应用潜力。