Nancy Awwad, Any Thy Bui, E. Danilov, F. Castellano
Summary Polymerization reactions initiated by ultraviolet light are ubiquitous in scores of industrial applications but would markedly benefit from visible-light activation to overcome stability, energy consumption, light penetration, and sample geometry limitations. The current work leverages visible-light-driven homomolecular triplet-triplet annihilation (TTA) in zinc(II) meso-tetraphenylporphyrin (ZnTPP) to initiate facile free-radical polymerization in trimethylolpropane triacrylate (TMPTA) and methyl acrylate (MA) monomers through ultrafast electron transfer quenching. Selective Q-band (S1) excitation of ZnTPP in the green or yellow sensitizes TTA occurring between two 3ZnTPP∗ energized chromophores, ultimately generating the highly reducing S2 excited state on one ZnTPP molecule (Ered = −2.13 V versus saturated calomel electrode, SCE). Subsequently, this S2 state engages in electron transfer with TMPTA or MA, thereby initiating the radical polymerization process. Bimolecular electron transfer was confirmed through optically gated fluorescence upconversion. FT-IR and EPR spin-trapping experiments verified visible-light-initiated polymerization leading to the formation of well-defined macro- and microscopic objects.
由紫外光引发的聚合反应在工业应用中无处不在，但可见光激活将明显有利于克服稳定性、能耗、光穿透性和样品几何形状的限制。本研究利用可见光驱动的中四苯基卟啉锌(ZnTPP)的均分子三重湮灭(TTA)，通过超快电子转移猝灭引发三甲基丙烷三丙烯酸酯(TMPTA)和丙烯酸甲酯(MA)单体的易自由基聚合。ZnTPP在绿色或黄色的选择性q带(S1)激发使两个3ZnTPP∗通电的发色团之间发生的TTA敏化，最终在一个ZnTPP分子上产生高度还原的S2激发态(Ered = - 2.13 V vs饱和甘汞电极，SCE)。随后，这个S2态与TMPTA或MA进行电子转移，从而启动自由基聚合过程。通过光门控荧光上转换证实了双分子电子转移。FT-IR和EPR自旋捕获实验证实了可见光引发的聚合导致形成定义良好的宏观和微观物体。
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