Sprecher
Beschreibung
Block copolymer gradient brushes: A detailed look at the synthesis and characterization
Jonah Decker1, Sören Steup2, Sergey I. Druzhinin1, Heiko Ihmels2, Holger Schönherr1*
1 Physical Chemistry I, Department of Chemistry and Biology and Research Center of Micro and Nanochemistry and (Bio)Technology (Cμ), University of Siegen
2 Organic Chemistry II, Department of Chemistry and Biology and Research Center of Micro and Nanochemistry and (Bio)Technology (Cμ), University of Siegen
E-mail: schoenherr@chemie.uni-siegen.de
In the SPP project, we develop polymer brush architectures to be able to study the dynamics of wetting by analysing the fluorescence dynamics of a solvatochromic reporter dye. Specifically we focus on poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA) brushes with an overall uniform height, containing a solvatochromic dye, which is able to probe the local polarity in its vicinity [1]. This dye should be covalently attached to the brushes in a one-dimensional depth gradient, which allows one to image the wetting dynamics with confocal fluorescence microscopy both with high lateral as well as significantly enhanced axial resolution. In this contribution we focus on the details of the synthesis and characterization PDEGMA brushes. Gradient brushes [2] were successfully synthesized via surface-initiated activator regenerated by electron transfer, atom transfer radical polymerization (SI-ARGET ATRP) with inverse gradient directions exploiting two consecutive polymerizations in which the substrate is immersed for different times in the polymerization solution. This was realized by pumping the corresponding solution into a reactor, in which the substrates were placed vertically. In this contribution, details on the polymerization of linear gradient brushes with dry thicknesses from 50 nm up to 400 nm, the addition of a thin second block by conventional atom transfer radical polymerization (ATRP) of a different monomer on top of the gradient brushes and the final gradient brush polymerization with inverse direction as third block to obtain an overall uniform height with a reinitiation efficiency > 80% will be presented. The middle block may contain the reporter dye moieties. The samples were characterized after each step of this block copolymer brush synthesis by ellipsometry, X-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, static and dynamic contact angle measurements and atomic force microscopy (AFM). In the future the incorporation of dye methacrylates into the gradient brush architecture will be attempted, to finally investigate the wetting dynamics of these polymer brush systems.
The authors gratefully acknowledge the financial support by the Deutsche Forschungsgemeinschaft (DFG in the SPP 2171, SCHO 1124/8-1) and the University of Siegen.
References
[1] A. Yadigarli, Q. Song,S. I. Druzhinin, H. Schönherr, Beilstein J. Org. Chem. 2019, 15, 2552.
[2] S. Großhans, I. Lilge, H. Schönherr, Macromol. Biosci. 2018, 18 (2), 1700317.