Polymerization process of hydrogel microspheres on video
Credit: Reprinted with permission from Langmuir 2021, 37, 151-159. Copyright (2021) American Chemical Society
Aqueous free-radical precipitation polymerization is one of the most useful methods to prepare the uniformly sized hydrogel microspheres (microgels), and an understanding of the polymerization mechanism is crucial to control the structure or physicochemical properties of microgels. However, the details of the mechanism of precipitation polymerization remain unclear.
Thus, first author Yuichiro Nishizawa, Prof. Daisuke Suzuki of the Graduate School of Textile Science & Technology, Shinshu University and Prof. Takayuki Uchihashi of Nagoya University set out to clarify the formation mechanism of microgels during precipitation polymerization by evaluating structural evolution and thermoresponsiveness of developing microgels during the polymerization and by visualization of polymerization directly.
Through the direct visualization of the microgels with different polymerization times, it was clarified that some inhomogeneous, non-thermoresponsive nanostructures existed in the thermoresponsive microgels formed in the initial stages of precipitation polymerization (Figure 1).
This result indicates that the aggregation of precipitated polymer chains in the nucleation process (the initial stages of the polymerization) is an important factor in determining the nanostructures of microgels.
With this study published in Langmuir, the research group succeeded in the direct visualization of the precipitation polymerization in real-time and obtained definitive evidence for understanding the formation mechanism of microgels during this polymerization (Video 1).
Nishizawa hopes to clarify what parameter is important for controlling the aggregation of polymer chain during precipitation polymerization, and ultimately, solve the mystery of the formation of uniformly sized microgels.
Daisuke Suzuki acknowledges Grants-in-Aid for Scientific Research on Innovative Areas (26102517, 16H00760, and 19H05388) and a Grant-in-Aid for Young Scientists (A) (JSPS; 17H04892) from the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). Takayuki Uchihashi acknowledges Grants-in-Aid for Scientific Research on Innovative Areas (26102515 and 18H04512) from MEXT. Yuichiro Nishizawa acknowledges a fellowship from the Japan Society for Promotion of Science (JSPS; 20J1272700).
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