Imaging Chemical Kinetics of Radical Polymerization with an Ultrafast Coherent Raman Microscope

Haozheng Li; Yong Cheng; Huajun Tang; Yali Bi; Yage Chen; Guang Yang; Shoujing Guo; Sidan Tian; Jiangshan Liao; Xiaohua Lv; Shaoqun Zeng; Mingqiang Zhu; Chenjie Xu; Ji-Xin Cheng; Ping Wang

doi:10.1002/advs.201903644

Imaging Chemical Kinetics of Radical Polymerization with an Ultrafast Coherent Raman Microscope

Adv Sci (Weinh). 2020 Mar 9;7(10):1903644. doi: 10.1002/advs.201903644. eCollection 2020 May.

Authors

Haozheng Li^{1

2}, Yong Cheng^{1

2}, Huajun Tang^{1

2}, Yali Bi^{1

2}, Yage Chen^{1

2}, Guang Yang^{1

2}, Shoujing Guo^{1

2}, Sidan Tian^{1

2}, Jiangshan Liao^{1

2}, Xiaohua Lv^{1

2}, Shaoqun Zeng^{1

2}, Mingqiang Zhu^{1

2}, Chenjie Xu³, Ji-Xin Cheng⁴, Ping Wang^{1

2}

Affiliations

¹ Britton Chance Center for Biomedical Photonics Wuhan National Laboratory for Optoelectronics Huazhong University of Science and Technology Wuhan Hubei 430074 China.
² MoE Key Laboratory for Biomedical Photonics Collaborative Innovation Center for Biomedical Engineering School of Engineering Sciences Huazhong University of Science and Technology Wuhan Hubei 430074 China.
³ School of Chemical and Biomedical Engineering Nanyang Technological University Singapore 637457 Singapore.
⁴ Department of Biomedical Engineering Boston University Boston MA 02215 USA.

Abstract

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.

Keywords: chemical kinetics; polymer synthesis; radical polymerization; stimulated Raman scattering; ultrafast chemical imaging; vibrational spectroscopy.