Shear-Induced Structural and Functional Transformations of Poly( N -vinylcaprolactam) Microgels

ACS Applied Polymer Materials, vol. 2, pp. 1682–1691

Abstract

Abstract We here performed an in-depth investigation of the behavior of microgels (μgels) and their associated physicochemical transformations under shear force. Thermo- and mechanoresponsive poly(N-vinylcaprolactam) (PVCL) μgels (d ∼ 400 nm) cross-linked with a force-responsive mechanofluorophore in different cross-linking degrees were synthesized and examined. Fluorescence spectroscopy (FS), confocal laser scanning microscopy (CLSM), dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryoTEM), high-resolution magic-angle sample spinning (HRMAS) nuclear magnetic resonance (NMR), Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) are used to characterize the μgels before, during, and after shearing with different shear rates and intensities. The obtained results suggest nonuniform structural features consisting of a softer outer “corona” and a harder particle “core” (cross-linker-rich). Upon shearing, the μgels rapidly lose their corona and the cores agglomerate altering μgel functionality. Surprisingly, μgels degrade promptly, even when subjected to low shear forces, such as the extrusion through a needle. This has potential implications for all applications in which shear forces in solution are expected, including extrusion, injection, and filtration processes involving colloidal μgel solutions as well as circulation within the bloodstream of living organisms.

Authors 6

1. Emilia Izak‐Nau Aachen DWI - Leibniz Institute for Interactive Materials

   DWI – Leibniz Institute for Interactive Materials

   Affiliation as printed

   DWI − Leibniz Institute for Interactive Materials , ,

   DWI − Leibniz Institute for Interactive Materials, 52056 Aachen, Germany

2. Dan E. Demco Aachen DWI - Leibniz Institute for Interactive Materials

   Technical University of Cluj-Napoca · DWI – Leibniz Institute for Interactive Materials

   Affiliation as printed

   DWI − Leibniz Institute for Interactive Materials , ,

   Technical University of Cluj-Napoca , , ,

   DWI − Leibniz Institute for Interactive Materials, 52056 Aachen, Germany

   Department of Physics and Chemistry, Technical University of Cluj-Napoca, 400027 Cluj-Napoca, Romania

3. Susanne Braun Aachen DWI - Leibniz Institute for Interactive Materials Institute for Technical and Macromolecular Chemistry

   DWI – Leibniz Institute for Interactive Materials · RWTH Aachen University

   Affiliation as printed

   DWI − Leibniz Institute for Interactive Materials , ,

   RWTH Aachen University , , ,

   Institute for Technical and Macromolecular Chemistry, RWTH Aachen University, 52074 Aachen, Germany

4. Christoph Baumann Aachen DWI - Leibniz Institute for Interactive Materials Institute for Technical and Macromolecular Chemistry

   DWI – Leibniz Institute for Interactive Materials · RWTH Aachen University

   Affiliation as printed

   DWI − Leibniz Institute for Interactive Materials , ,

   RWTH Aachen University , , ,

   Institute for Technical and Macromolecular Chemistry, RWTH Aachen University, 52074 Aachen, Germany

5. Andrij Pich Aachen DWI - Leibniz Institute for Interactive Materials Institute for Technical and Macromolecular Chemistry

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

   Affiliation as printed

   DWI − Leibniz Institute for Interactive Materials , ,

   Maastricht University , , Brightlands Chemelot Campus, ,

   RWTH Aachen University , , ,

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

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

   Institute for Technical and Macromolecular Chemistry, RWTH Aachen University, 52074 Aachen, Germany

6. Robert Göstl corresponding Aachen DWI - Leibniz Institute for Interactive Materials

   DWI – Leibniz Institute for Interactive Materials

   Affiliation as printed

   DWI − Leibniz Institute for Interactive Materials , ,

   DWI − Leibniz Institute for Interactive Materials, 52056 Aachen, Germany