Photo-Induced Polymerization Reactions: Quantitative Information via Mass Spectrometry and Femtosecond Pump-Probe Absorption Studies

目前的延期申请建立在DFG过去两年半资助的关于通过电喷雾电离质谱（ESI-MS）定量光解产生的自由基对乙烯单体的反应性的主题的工作基础上。通过提供与来自不同光引发剂的单个自由基片段相关的相对净引发比，为实现对光引发过程的深入定量理解奠定了基础。在研究过程中，我们意外地发现，飞秒光谱与脉冲激光聚合排粒径色谱ESI-MS （PLP-SEC-ESI-MS）实验相结合，不仅可以深入了解自由基片段的相对净效率，而且可以将观察到的净效率与受激分子内部能量分布（即激光激发后单重态到三重态系统间交叉的效率）联系起来。最初的资助导致了9个启动系统的研究，导致了4个同行评审的研究成果（以及额外的即将出版的手稿），这些成果突出了我们结合实验方法的力量，首次产生了关于光引发剂及其内部能量耗散通道净效率的定量知识。在请求的扩展项目中，我们现在希望在KIT聚合物研究所和物理化学研究所之间的合作项目中利用我们的联合实验装置。主要目的是通过现已建立的PLP-SEC-ESI-MS技术对广泛的自由基片段进行定量确定相对净起始效率，并对构成引发剂分子的系统间交叉行为进行定量理解，以获得依赖于起源的自由基片段起始效率图。我们认为，这是一个独特的机会，可以第一次全面全面地了解光解产生的自由基片段的最终聚合物端基分布和光引发剂内部依赖于结构的内能转换。

The current extension request builds on the work of the past 2.5 years funded by the DFG on the topic of Quantifying the Reactivity of Photolytically Generated Radicals Towards Vinylic Monomers via Electrospray Ionization Mass Spectrometry (ESI-MS), where the foundation was laid for achieving an in-depth quantitative understanding of photo-initiation processes via the provision of relative net initiation ratios associated with individual radical fragments originating from various photoinitiators. In the course of the research we found unexpectedly that femtosecond spectroscopy in combination with the pulsed laser polymerization size-exclusion chromatography ESI-MS (PLP-SEC-ESI-MS) experiments yield not only insights into the relative net efficiency of a radical fragment, but also allows to correlate the observed net efficiencies with the internal energy distribution within the excited molecule, i.e. the efficiency of the singlet to triplet intersystem crossing after laser excitation. The original grant has led to the study of 9 initiation systems leading to 4 peer-reviewed research outputs (as well as additional forthcoming manuscripts) that highlight the power of our combined experimental approach to for the first time generate quantitative knowledge about net efficiencies of photoinitiators with their internal energy dissipation channels. Within the requested extension project, we now wish to exploit our combined experimental set-up in a collaborative project between the KIT Polymer and Physical Chemistry institutes. The key aim is the quantitative determination of the relative net initiation efficiency via the now established PLP-SEC-ESI-MS technique for a wide range of radical fragments coupled with the quantitative understanding of the intersystem crossing behavior of the constituting initiator molecules, to arrive at a map of origin dependent radical fragment initiation efficiencies. We believe that a unique opportunity exists to for the first time provide a full and comprehensive understanding of final polymer end group distribution of photolytically generated radical fragments with the structure dependent internal energy conversion within the photoinitiators.