Mechanically Resistant Poly(N‐vinylcaprolactam) Microgels with Sacrificial Supramolecular Catechin Hydrogen Bonds

Advanced Science, vol. 9, pp. e2104004

Abstract

Microgels (μgels) swiftly undergo structural and functional degradation when they are exposed to shear forces, which potentially limit their applicability in, e.g., biomedicine and engineering. Here, poly(N-vinylcaprolactam) μgels that resist mechanical disruption through supramolecular hydrogen bonds provided by (+)-catechin hydrate (+C) are synthesized. When +C is added to the microgel structure, an increased resistance against shear force exerted by ultrasonication is observed compared to μgels crosslinked by covalent bonds. While covalently crosslinked μgels degrade already after a few seconds, it is found that μgels having both supramolecular interchain interactions and covalent crosslinks show the highest mechanical durability. By the incorporation of optical force probes, it is found that the covalent bonds of the μgels are not stressed beyond their scission threshold and mechanical energy is dissipated by the force-induced reversible dissociation of the sacrificial +C bonds for at least 20 min of ultrasonication. Additionally, +C renders the μgels pH-sensitive and introduces multiresponsivity. The μgels are extensively characterized using Fourier-transform infrared, Raman and quantitative nuclear magnetic resonance spectroscopy, dynamic light scattering, and cryogenic transmission electron microscopy. These results may serve as blueprint for the preparation of many mechanically durable μgels.

Authors 4

1. Emilia Izak‐Nau Aachen

   DWI – Leibniz Institute for Interactive Materials

   Affiliation as printed

   DWI – Leibniz Institute for Interactive Materials Forckenbeckstr. 50 Aachen 52056 Germany

2. Susanne Braun Aachen Institute of Technical and Macromolecular Chemistry

   DWI – Leibniz Institute for Interactive Materials · RWTH Aachen University

   Affiliation as printed

   DWI – Leibniz Institute for Interactive Materials Forckenbeckstr. 50 Aachen 52056 Germany

   Institute of Technical and Macromolecular Chemistry RWTH Aachen University Worringerweg 1 Aachen 52074 Germany

   Institute of Technical and Macromolecular Chemistry RWTH Aachen University Worringerweg 1 Aachen 52074 Germany

3. Andrij Pich Aachen Institute of Technical and Macromolecular Chemistry

   Maastricht University · DWI – Leibniz Institute for Interactive Materials · RWTH Aachen University

   Affiliation as printed

   Aachen Maastricht Institute for Biobased Materials (AMIBM) Maastricht University Brightlands Chemelot Campus Geleen 6167 RD The Netherlands

   DWI – Leibniz Institute for Interactive Materials Forckenbeckstr. 50 Aachen 52056 Germany

   Institute of Technical and Macromolecular Chemistry RWTH Aachen University Worringerweg 1 Aachen 52074 Germany

   Aachen Maastricht Institute for Biobased Materials (AMIBM) Maastricht University Brightlands Chemelot Campus Geleen 6167 RD The Netherlands

   Institute of Technical and Macromolecular Chemistry RWTH Aachen University Worringerweg 1 Aachen 52074 Germany

4. Robert Göstl corresponding Aachen

   DWI – Leibniz Institute for Interactive Materials

   Affiliation as printed

   DWI – Leibniz Institute for Interactive Materials Forckenbeckstr. 50 Aachen 52056 Germany