School of Electronic and Information Engineering, Harbin Institute of Technology, Shenzhen 518055, China.
Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Sci Adv. 2023 May 10;9(19):eadf1725. doi: 10.1126/sciadv.adf1725.
Understanding the diffusion of small molecules in polymer microsystems is of great interest in diverse fundamental and industrial research. Despite the rapidly advancing optical imaging and spectroscopic techniques, entities under investigation are usually limited to flat films or bulky samples. We demonstrate a route to in situ detection of diffusion dynamics in polymer micro-objects by means of optical whispering-gallery mode resonances. Through mode tracking, interactions between solvent molecules and polymer microspheres, including sorption, diffusion, and swelling can be quantitatively analyzed. A turning point of mode response is observed, while the diffusion exceeds the sub-wavelength-thick outermost layer as the radial extent of resonances and starts penetrating the inner core. The estimated solubility in the glassy polymer is consistent with the predicted value using Flory-Huggins theory. Besides, the non-Fickian contribution is analyzed in such a glassy polymer-penetrant system. Our work represents a high-precision and label-free approach to describing characteristics in diffusion dynamics.
理解小分子在聚合物微系统中的扩散在各种基础研究和工业研究中都具有重要意义。尽管光学成像和光谱技术在快速发展，但研究对象通常仅限于平板膜或大块样品。我们展示了一种通过光学 whispering-gallery 模式共振原位检测聚合物微物体扩散动力学的方法。通过模式跟踪，可以定量分析溶剂分子与聚合物微球之间的相互作用，包括吸附、扩散和溶胀。当扩散超过亚波长厚的最外层时，共振的径向范围开始穿透内芯，观察到模式响应的转折点。在玻璃态聚合物中的估计溶解度与使用 Flory-Huggins 理论预测的值一致。此外，还分析了这种玻璃态聚合物-渗透剂体系中的非 Fickian 贡献。我们的工作代表了一种高精度和无标记的方法来描述扩散动力学中的特性。
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