Photoinduced-RAFT polymerization is a technique of increasing interest due to the combination of control over polymerization that RAFT processes afford with the mild reaction conditions and spatial and temporal control of photochemical processes. Iniferter RAFT polymerization is an interesting subclass of photoinduced-RAFT that eliminates the need for an added photocatalyst, as the RAFT agent is directly excited by the photon source. Iniferter RAFT is a photochemical process leading to carbon–sulfur bond homolysis. In this work we find a surprising effect of substituents on the dithiobenzoate moiety of the chain transfer agent (CTA). Donating groups dramatically accelerate the iniferter process, while withdrawing groups retard the reaction substantially. This is interpreted though electrochemistry, since homolysis of the carbon–sulfur bond is associated with a formal oxidation of the thiocarbonylthio groups and reduction of the carbon to a radical. Through this study, the unique efficiency of 2-cyano-2-propyl 4-methoxydithiobenzoate (CPMODB) as an iniferter was uncovered, as this polymerization was found to progress at a drastically enhanced rate, even when compared to similar tris[2-phenylpyridinato-C²,N]iridium(III) photocatalyzed polymerizations using an unsubstituted dithiobenzoate RAFT agent.

中文翻译：

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引发剂光聚合反应中的取代基效应：电子可以增强键的均相吗？

由于RAFT过程提供的对聚合的控制与温和的反应条件以及光化学过程的时空控制的结合，光诱导RAFT聚合是一种越来越引起人们关注的技术。Iniferter RAFT聚合是光引发RAFT的一个有趣的子类，由于RAFT剂直接被光子源激发，因此无需添加光催化剂。Iniferter RAFT是一种光化学过程，可导致碳硫键均裂。在这项工作中，我们发现了取代基对链转移剂（CTA）的二硫代苯甲酸酯部分的惊人影响。供体基团极大地加速了引发者的进程，而供体基团则大大阻碍了反应。这是通过电化学来解释的，因为碳硫键的均质分解与硫代羰基硫基团的形式氧化和碳还原为自由基有关。通过这项研究，发现了2-氰基-2-丙基4-甲氧基二硫代苯甲酸酯（CPMODB）作为引发剂的独特效率，因为发现该聚合反应以显着提高的速度进行，即使与类似的三[2-苯基吡啶并酮-C^{如图2所示}，使用未取代的二硫代苯甲酸酯RAFT剂的N ]铱（ III）被光催化聚合。