Numerous mechanisms have been proposed for polymerization to provide qualitative and quantitative prediction of how monomers spatially and temporally arrange into the polymeric chains. However, less is known about this process at the molecular level because the ultrafast chemical reaction is inaccessible for any form of microscope so far. Here, to address this unmet challenge, a stimulated Raman scattering microscope based on collinear multiple beams (COMB-SRS) is demonstrated, which allows label-free molecular imaging of polymer synthesis in action at speed of 2000 frames per second. The field of view of the developed 2 kHz SRS microscope is 30 × 28 µm2 with 50 × 46 pixels and 7 µs dwell time. By catching up the speed of chemical reaction, COMB-SRS is able to quantitatively visualize the ultrafast dynamics of molecular vibrations with submicron spatial resolution and sub-millisecond temporal resolution. The propagating polymer waves driven by reaction rate and persistent UV initiation are observed in situ. This methodology is expected to permit the development of novel functional polymers, controllable photoresists, 3D printing, and other new polymerization technologies.

中文翻译：

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使用超快相干拉曼显微镜对自由基聚合的化学动力学进行成像。

人们已经提出了许多聚合机制，以提供单体如何在空间和时间上排列成聚合物链的定性和定量预测。然而，人们对分子水平上的这一过程知之甚少，因为迄今为止任何形式的显微镜都无法实现超快的化学反应。在这里，为了解决这一未解决的挑战，展示了一种基于共线多光束 (COMB-SRS) 的受激拉曼散射显微镜，它允许以每秒 2000 帧的速度对聚合物合成进行无标记分子成像。所开发的 2 kHz SRS 显微镜的视场为 30 × 28 µm2，具有 50 × 46 像素和 7 µs 停留时间。通过追赶化学反应的速度，COMB-SRS 能够以亚微米空间分辨率和亚毫秒时间分辨率定量可视化分子振动的超快动力学。在原位观察到由反应速率和持续紫外线引发驱动的传播聚合物波。该方法预计将允许开发新型功能聚合物、可控光刻胶、3D 打印和其他新聚合技术。