Tetraphenylethene Cross-Linked Thermosensitive Microgels via Acylhydrazone Bonds: Aggregation-Induced Emission in Nanoconfined Environments and the Cononsolvency Effect,Macromolecules

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Tetraphenylethene Cross-Linked Thermosensitive Microgels via Acylhydrazone Bonds: Aggregation-Induced Emission in Nanoconfined Environments and the Cononsolvency Effect
Macromolecules ( IF 5.1 ) Pub Date : 2018-07-24 00:00:00 , DOI: 10.1021/acs.macromol.8b01100
Jinqiao Xue , Wei Bai , Hanyi Duan , Jingjing Nie , Binyang Du , Jing Zhi Sun , Ben Zhong Tang ₁

Affiliation

We studied the aggregation-induced emission (AIE) phenomenon in a nanoconfined environment, where the AIE-active molecule, namely, 1,1,2,2-tetrakis(4-methanoylphenyl)ethane (TPE-4ALD), was held in space via four acylhydrazone bonds within the thermosensitive microgel networks. The thermosensitive microgels, namely N-AH-TPE, were synthesized via the copolymerization of N-isopropylacrylamide (NIPAM) and 4-acylhydrazine-(2-hydroxy-3-(methacryloxypropyl)pyridine hydrochloride (AH monomer) with TPE-4ALD as cross-linker via surfactant free emulsion polymerization (SFEP) in aqueous solution at 70 °C. Acylhydrazone-bonded tetraphenylethene (TPE-4AH) moieties were thus constructed and worked as the fluorophore in N-AH-TPE microgels. The aqueous suspensions of N-AH-TPE microgels exhibit strongly bluish-green fluorescence under ultraviolet excitation because the four arms of TPE-4AH moieties were held and their intramolecular motions are strongly restricted. It is estimated that there is one TPE-4AH moiety per about 394 nm³ for the swollen N-AH-TPE microgels. The fluorescent properties of N-AH-TPE microgels can be modulated via the change of hydrophilic and hydrophobic environments of TPE-4AH moieties exerted by external stimuli, like addition of various good solvents for TPE-based structures, i.e., N,N-dimethylformamide (DMF), methanol, ethanol, tetrahydrofuran (THF), and N,N-dimethyl sulfoxide (DMSO), varying the solution temperature as well as the counteranions of the microgels. An unusual enhancement in the fluorescent intensity is observed when specific amounts of organic solvent are added into the aqueous suspensions of N-AH-TPE microgels, which can be attributed to the cononsolvency of the polyNIPAM network chains. The shrinkage of N-AH-TPE microgels caused by the cononsolvency effect further strengthens the confinement of TPE-4AH moieties and hence enhances the fluorescent emission of the microgels even though the organic solvents added are good solvents for TPE-4AH. Increasing the solution temperature of N-AH-TPE microgels or introducing hydrophobic counteranions into the microgels also significantly enhances the fluorescent emission of the microgels.

中文翻译：

四苯乙炔通过via键交联的热敏微凝胶：纳米受限环境中的聚集诱导发射和亲和力效应

我们研究了在纳米密闭环境中的聚集诱导发射（AIE）现象，其中AIE活性分子，即1,1,2,2-四（4-甲酰基苯基）乙烷（TPE-4ALD）被保留在太空中通过热敏性微凝胶网络中的四个酰基hydr键。通过N的共聚合成热敏性微凝胶，即N-AH-TPE。-异丙基丙烯酰胺（NIPAM）和4-酰基肼-（2-羟基-3-（甲基丙烯酰氧基丙基）吡啶盐酸盐（AH单体）与TPE-4ALD作为交联剂，通过无表面活性剂乳液聚合（SFEP）在70°C的水溶液中进行。因此，构建了与乙bon键合的四苯基乙烯（TPE-4AH）部分，并作为N-AH-TPE微凝胶中的荧光团；由于紫外线的四个臂，N-AH-TPE微凝胶的水悬浮液在紫外线激发下显示出强烈的蓝绿色荧光。保留了TPE-4AH部分，并且强烈限制了它们的分子内运动，估计每394 nm ³存在一个TPE-4AH部分³用于溶胀的N-AH-TPE微凝胶。N-AH-TPE微凝胶的荧光性质可以通过外部刺激施加的TPE-4AH部分的亲水和疏水环境的变化来调节，例如为TPE基结构添加各种良好的溶剂，例如N，N-二甲基甲酰胺（DMF），甲醇，乙醇，四氢呋喃（THF）和N，N-二甲基亚砜（DMSO），改变溶液温度以及微凝胶的抗衡阴离子。当将特定量的有机溶剂添加到N-AH-TPE微凝胶的水性悬浮液中时，观察到荧光强度的异常增强，这可以归因于polyNIPAM网络链的共溶性。由共溶作用引起的N-AH-TPE微凝胶的收缩进一步增强了TPE-4AH部分的封闭性，因此即使所添加的有机溶剂是TPE-4AH的良好溶剂，也增强了微凝胶的荧光发射。提高N-AH-TPE微凝胶的溶液温度或将疏水性抗衡阴离子引入微凝胶中，也会显着增强微凝胶的荧光发射。

更新日期：2018-07-24

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