Fluorophore is essential to enable the fluorescence and optical switching in most of polymer gels. Herein, a novel concept is proposed to develop a fluorophore-free organogel that is capable of generation of blue fluorescence at transparent state, while it proceeds with optical switching from blue to purple upon phase transition into non-transparent state in water. Ammonium persulphate (APS) is utilized to initiate co-crosslinking of hydrophilic acrylamide (AM) and hydrophobic 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA) in dimethyl sulphoxide (DMSO) to give organogel of AM@HFBA at 80 °C. APS decomposes to generate not only radicals, but also ammonium bisulfate (ABS) during heating, in which the elements of ABS produce blue fluorescence (λ = 440 nm), excited by UV light (λ = 365 nm). After the phase transition into non-transparent state, light-reflection behavior at the phase-transitioned surface triggers the optical switching of the organogel from blue to purple under UV light. The optical switching is patternable and reversible, which enables the applications of organogel of AM@HFBA for information encoding/encryption and optical-switchable soft actuators. This method is universal to achieve fluorescence and optical switching for free radical polymerization-based gel systems as long as they are initiated by APS in DMSO.

中文翻译：

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无荧光团有机凝胶的荧光机理和光开关

荧光团对于在大多数聚合物凝胶中实现荧光和光学切换至关重要。在此，提出了一个新的概念来开发一种无荧光团的有机凝胶，它能够在透明状态下产生蓝色荧光，同时在水中相变到非透明状态时进行从蓝色到紫色的光学转换。过硫酸铵 (APS) 用于引发亲水性丙烯酰胺 (AM) 和疏水性 2,2,3,4,4,4-六氟丁基丙烯酸酯 (HFBA) 在二甲基亚砜 (DMSO) 中的共交联，得到 AM@HFBA 有机凝胶在 80 °C。APS在加热过程中分解不仅产生自由基，还会产生硫酸氢铵（ABS），其中ABS的元素在紫外光（ λ ） 激发下产生蓝色荧光（ λ = 440 nm ） = 365 纳米）。在相变到非透明状态后，相变表面的光反射行为触发有机凝胶在紫外光下从蓝色到紫色的光学转换。光开关是可图案化和可逆的，这使得 AM@HFBA 的有机凝胶在信息编码/加密和光开关软执行器方面的应用成为可能。这种方法对于基于自由基聚合的凝胶系统实现荧光和光学切换是通用的，只要它们由 DMSO 中的 APS 启动即可。