Polymer Chemistry Research Group, Centre of Macromolecular Chemistry (CMaC), Department of Organic and Macromolecular Chemistry , Ghent University , Krijgslaan 281 S4-bis , 9000 Gent , Belgium.
School of Chemistry, Physics and Mechanical Engineering , Queensland University of Technology (QUT) , 2 George Street , Brisbane , Queensland 4000 , Australia.
J Am Chem Soc. 2019 Aug 7;141(31):12329-12337. doi: 10.1021/jacs.9b05092. Epub 2019 Jul 10.
The light-responsive adaptation of polymer materials typically requires different wavelengths or additional heat to induce reversible covalent bond formation and dissociation. Here, we bypass the use of invasive triggers by introducing light-stabilized dynamic materials that can undergo a repeatable change in topology from a covalently cross-linked material into a liquid polymer formulation by switching one visible light source on-and-off without the need for any additional triggers. Specifically, we exploit the photo-Diels-Alder reaction of triazolinediones with naphthalenes as a dynamic covalent cross-linking platform that enables green light-induced network formation, while the cross-linked material collapses through spontaneous cycloreversion upon standing in the dark at ambient temperature. Importantly, the covalent cross-links remain stabilized for as long as visible light is present, thereby retaining the material's structural integrity. This enables their potential use in an array of light-directed applications whereby network properties such as stiffness can be tuned by the mildest trigger of all: darkness.
聚合物材料的光响应适应性通常需要不同的波长或额外的热量来诱导可逆的共价键形成和断裂。在这里，我们通过引入光稳定的动态材料来避免使用侵入性的触发物，这些材料可以通过打开和关闭一个可见光源，从共价交联材料重复地转变为液体聚合物配方，而无需任何额外的触发物。具体来说，我们利用三唑啉二酮与萘的光二烯加成反应作为动态共价交联平台，实现绿光诱导的网络形成，而交联材料在黑暗中静置在环境温度下会通过自发环化回复而坍塌。重要的是，只要可见光存在，共价交联就会保持稳定，从而保持材料的结构完整性。这使得它们有可能在一系列光导向应用中使用，其中网络性质（如硬度）可以通过最温和的触发物（即黑暗）进行调节。
