Homma Kenta, Ohta Yuji, Minami Kosuke, Yoshikawa Genki, Nagase Kenichi, Akimoto Aya M, Yoshida Ryo
Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
School of Humanities and Science, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan.
Langmuir. 2021 Apr 13;37(14):4380-4386. doi: 10.1021/acs.langmuir.1c00459. Epub 2021 Apr 1.
As a novel functional surface, a self-oscillating polymer brush that undergoes autonomous, periodic swelling/deswelling during the Belousov-Zhabotinsky (BZ) reaction has been developed. Although extensive research has revealed how the fundamental aspects of the BZ reaction can be regulated based on the surface design of the self-oscillating polymer brush, design strategies for the induction of mechanical oscillation remain unexplored. Herein, we investigated the graft density effects on the phase transition behavior, which is an important design parameter for the mechanical oscillation of the modified polymer. The self-oscillating polymer-modified substrates with controlled graft densities were prepared by immobilizing various compositions of an initiator and a noninitiator followed by surface-initiated atom transfer radical polymerization of the self-oscillating polymer chains. In addition to the characterization of each prepared substrate, atomic force microscopy (AFM) and digital holographic microscopy (DHM) were employed to evaluate the density effects on the static and dynamic surface structures. AFM revealed that equilibrium swelling as well as thermoresponsive behavior is profoundly affected by the graft density. Moreover, using DHM, autonomous mechanical oscillation was captured only on the self-oscillating polymer brush with adequate graft density. Notably, the oscillation amplitude (150 nm) and the period (20 s) in this study were superior to those in a previous report on the self-oscillating polymer modified through the grafting-to method by 10- and 3-fold, respectively. This study presents design guidelines for future applications, such as autonomous transport devices.
作为一种新型功能表面，已开发出一种在贝洛索夫-扎博廷斯基（BZ）反应过程中经历自主周期性溶胀/去溶胀的自振荡聚合物刷。尽管大量研究揭示了如何基于自振荡聚合物刷的表面设计来调控BZ反应的基本方面，但诱导机械振荡的设计策略仍未得到探索。在此，我们研究了接枝密度对相变行为的影响，相变行为是改性聚合物机械振荡的一个重要设计参数。通过固定引发剂和非引发剂的各种组成，然后进行自振荡聚合物链的表面引发原子转移自由基聚合，制备了具有可控接枝密度的自振荡聚合物改性基底。除了对每个制备的基底进行表征外，还采用原子力显微镜（AFM）和数字全息显微镜（DHM）来评估密度对静态和动态表面结构的影响。AFM显示平衡溶胀以及热响应行为都受到接枝密度的深刻影响。此外，使用DHM，仅在具有适当接枝密度的自振荡聚合物刷上捕捉到了自主机械振荡。值得注意的是，本研究中的振荡幅度（150 nm）和周期（20 s）分别比先前关于通过接枝法改性的自振荡聚合物的报告中的值高出10倍和3倍。本研究为未来应用（如自主运输装置）提供了设计指导方针。
