Design of Self-Oscillating Polymer Brushes and Control of the Dynamic Behaviors

Abstract

A polymer brush surface with autonomous function has been designed by using a self-oscillating polymer that we developed. The self-oscillation is induced by chemomechanical energy conversion from an oscillating chemical reaction (the Belousov−Zhabotinsky (BZ) reaction) to conformational changes of polymer chains. In this study, the surface nanostructure of polymer brushes were regulated and the spatiotemporal behaviors of self-oscillation were investigated. The target polymer brush surfaces were prepared through surface-initiated atom transfer radical polymerization (SI-ATRP) of N-isopropylacrylamide (NIPAAm) and N-(3aminopropyl) methacrylamide (NAPMAm), and the subsequent conjugation of Ru(bpy) 3 to the amino group of NAPMAm. The characterization of the prepared polymer brush and the free polymer was determined by X-ray photoelectron spectroscopy, atomic force microscopy, attenuated total reflection Fourier transform infrared spectroscopy, UV−vis spectrophotometry, gel permeation chromatography, and 1 H NMR. Their dynamic properties were estimated by quartz crystal microbalance with dissipation and fluorescence microscopy. The amounts of Ru(bpy) 3 immobilized to polymer brush surfaces could be controlled by adjusting the reaction conditions of SI-ATRP and conjugating Ru(bpy) 3 . Importantly, an appropriate structure of polymer brush to give stable oscillation has been indicated from image analysis of chemical wave propagation. Further, several physicochemical parameters to control the oscillating behaviors, including the rate constant of the autocatalytic reaction, the diffusion constant of the activator, and the activation energies for the reaction and diffusion, have been obtained from theoretical consideration. These results will be helpful for developing subsequent applications such as autonomous transport systems.

Fabrication of Micropatterned Self‐Oscillating Polymer Brush for Direction Control of Chemical Waves

“…This peak was derived from the amide I stretching vibration of the modified polymer chains. [20] The elemental composition analyses conducted by XPS also revealed the same tendency ( Figure S2, Supporting Information). By comparing the small-range scans for C(1s) and N(1s) from the two substrates, it was found that the compositions on the photoresist-coated substrate were larger than those of the photoresist-uncoated substrate for both elements.…”

“…[9,10] (2 of 8) 1700041 www.small-journal.com for mass transport or fluid control. [20] However, because the BZ substrates were homogeneously distributed in the BZ medium, the propagation of the chemical waves was not in a single well-defined direction, which can be a drawback considering this phenomenon's potential applications as a mass transport system. We recently reported that incorporating a gradient structure into the self-oscillating polymer brush by the sacrificial-anode ATRP method can overcome this issue.…”

“…[26] The amount of Ru(bpy) 3 conjugated to the tethered polymer chains was estimated to be 3.4 nmol cm −2 based on UV-vis measurements. This value was expected to be sufficient to induce the BZ reaction, according to previous work by Masuda et al [20] Next, in order to characterize the visible light irradiated area of the patterned self-oscillating polymer brush, an unpatterned polymer brush surface was prepared with all the photoresist removed using acetone before the oxygen plasma treatment. ATRP was performed after the oxygen plasma treatment.…”

“…[17,18] As another means to apply this autonomous material, here we introduced the self-oscillating polymer onto a glass surface as a self-oscillating polymer brush via surface-initiated atom transfer radical polymerization (SI-ATRP). [19,20] In a previous study, the self-oscillating polymer brushes have been shown to generate autonomous propagation of the excited pulse of the oxidized (i.e., hydrophilic, extended polymer chains) area due to a reaction-diffusion mechanism ("chemical wave"), which may serve as a driving force DOI: 10.1002/smll.201700041…”

Recent Advances in Self‐Oscillating Polymer Material Systems

“…Furthermore, to improve the self‐oscillating behaviors and obtain more stable oscillations, we have investigated the relationship between surface nano‐structures and the resulting oscillating behavior . Self‐oscillating polymer brushes with different architectures were prepared by changing synthesis conditions, and surface characterization was conducted by XPS and AFM measurement (Figure a).…”