Polymer Chemistry Research Group, Centre of Macromolecular Chemistry (CMaC), Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Krijgslaan 281 S4-bis, Ghent 9000, Belgium.
J Am Chem Soc. 2022 Apr 20;144(15):6954-6963. doi: 10.1021/jacs.2c01622. Epub 2022 Apr 11.
A fundamentally important characteristic of a macromolecule is its shape. Herein, visible light and darkness are used as the only stimuli to reversibly alter the topology of well-defined polymers in a one-pot procedure. For this, linear naphthalene-containing polyacrylates are used as scaffolds for the visible light-induced cycloaddition with various substituted triazolinediones (i.e., butyl, stearyl, perfluoro, and polymeric), resulting in differently shaped graft polymers, including brushes and combs. The thus-formed cycloadduct linkages dissociate in the dark, resulting in the regeneration of the parent linear polymer at ambient temperature, establishing a dual-topology transformation by only switching green light on and off. By applying different temperatures during the cycloreversion process, the dissociation rate of the cycloadducts can be tuned in a facile manner, thus allowing for time control over the regeneration of the parent polymer. By engineering a polymer that consists of differently substituted naphthalenes at the chain ends and on the side chains, the inherently different cycloreversion rates of the formed cycloadducts are leveraged to achieve in situ multi-topology transformations without external stimuli. The shape transformations have been repeated up to 4 times sequentially in one pot without the need of any purification. The topological alterations are microscopically depicted through reversible self-assembly, with the polymers adopting different morphologies upon visible light or darkness. The versatile yet practical nature of this polymer "reshaping" strategy provides facile access to multifaceted polymer systems and, consequently, to a plethora of potential applications thereof.
大分子的一个基本特征是其形状。在这里，可见光和黑暗被用作唯一的刺激物，以在一锅程序中可逆地改变定义良好的聚合物的拓扑结构。为此，使用含萘的线性聚丙烯酸酯作为支架，用于与各种取代的三唑啉二酮（即丁基、硬脂基、全氟和聚合）进行可见光诱导的环加成，得到不同形状的接枝聚合物，包括刷子和梳子。由此形成的环加成键在黑暗中解离，导致在环境温度下再生母体线性聚合物，通过仅打开和关闭绿光来建立双拓扑转变。通过在环回转化过程中施加不同的温度，可以以简单的方式调节环加成物的解离速率，从而可以控制母体聚合物的再生时间。通过设计一种聚合物，其链末端和侧链上含有不同取代的萘，利用形成的环加成物的固有不同的环回转化速率，实现无需外部刺激的原位多拓扑转变。在一个锅中无需任何纯化即可连续重复进行 4 次形状转变。通过可逆自组装微观描绘拓扑变化，聚合物在可见光或黑暗下呈现不同的形态。这种聚合物“重塑”策略的多功能性和实用性为多方面的聚合物系统提供了便捷的途径，从而为其提供了大量潜在的应用。
