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

Emilia Izak-Nau; Dan E. Demco; Susanne Braun; Christoph Baumann; Andrij Pich; Robert Goestl

doi:10.1021/acsapm.0c00111

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

Emilia Izak-Nau, Dan E. Demco, Susanne Braun, Christoph Baumann, Andrij Pich, Robert Goestl^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

We here performed an in-depth investigation of the behavior of microgels (mu gels) and their associated physicochemical transformations under shear force. Thermo- and mechanoresponsive poly(N-vinylcaprolactam) (PVCL) mu gels (d similar to 400 nm) cross-linked with a force-responsive mechanofluorophore in different crosslinking 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 mu gels 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 mu gels rapidly lose their corona and the cores agglomerate altering mu gel functionality. Surprisingly, mu gels 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 mu gel solutions as well as circulation within the bloodstream of living organisms.

Original language	English
Pages (from-to)	1682-1691
Number of pages	10
Journal	ACS Applied Polymer Materials
Volume	2
Issue number	4
DOIs	https://doi.org/10.1021/acsapm.0c00111
Publication status	Published - Apr 2020

Keywords

microgels
mechanical properties
shear force
mechanochemistry
colloids
RHEOLOGICAL PROPERTIES
INTERNAL STRUCTURE
MACROMOLECULES
TEMPERATURE
SUSPENSIONS
DENSITY

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10.1021/acsapm.0c00111Licence: CC BY-NC-ND

Cite this

@article{bb9d41c0eb7c4ec5b2943be8c9361e1c,

title = "Shear-Induced Structural and Functional Transformations of Poly(N-vinylcaprolactam) Microgels",

abstract = "We here performed an in-depth investigation of the behavior of microgels (mu gels) and their associated physicochemical transformations under shear force. Thermo- and mechanoresponsive poly(N-vinylcaprolactam) (PVCL) mu gels (d similar to 400 nm) cross-linked with a force-responsive mechanofluorophore in different crosslinking 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 mu gels 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 mu gels rapidly lose their corona and the cores agglomerate altering mu gel functionality. Surprisingly, mu gels 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 mu gel solutions as well as circulation within the bloodstream of living organisms.",

keywords = "microgels, mechanical properties, shear force, mechanochemistry, colloids, RHEOLOGICAL PROPERTIES, INTERNAL STRUCTURE, MACROMOLECULES, TEMPERATURE, SUSPENSIONS, DENSITY",

author = "Emilia Izak-Nau and Demco, {Dan E.} and Susanne Braun and Christoph Baumann and Andrij Pich and Robert Goestl",

note = "Funding Information: E.I.-N. and R.G. acknowledge financial support from the European Commission (EUSMI, No. 731019). R.G. and C.B. are grateful for support by a Freigeist-Fellowship of the Volkswagen Foundation (No. 92888). A.P. acknowledges funding from DFG SFB 985. Parts of the analytical investigations were performed at the Center for Chemical Polymer Technology CPT, which was supported by the European Commission and the federal state of North Rhine-Westphalia (No. 300088302). The authors wish to thank Dr. K. Rahimi, S. Rieder, and M. Maassen for the STEM/cryoTEM analysis and M. Merklinger for MFP synthesis. The authors acknowledge the use of XPS (J. Roes) and FTIR (B. Becker). Publisher Copyright: Copyright {\textcopyright} 2020 American Chemical Society.",

year = "2020",

month = apr,

doi = "10.1021/acsapm.0c00111",

language = "English",

volume = "2",

pages = "1682--1691",

journal = "ACS Applied Polymer Materials",

issn = "2637-6105",

publisher = "American Chemical Society",

number = "4",

}

TY - JOUR

T1 - Shear-Induced Structural and Functional Transformations of Poly(N-vinylcaprolactam) Microgels

AU - Izak-Nau, Emilia

AU - Demco, Dan E.

AU - Braun, Susanne

AU - Baumann, Christoph

AU - Pich, Andrij

AU - Goestl, Robert

N1 - Funding Information: E.I.-N. and R.G. acknowledge financial support from the European Commission (EUSMI, No. 731019). R.G. and C.B. are grateful for support by a Freigeist-Fellowship of the Volkswagen Foundation (No. 92888). A.P. acknowledges funding from DFG SFB 985. Parts of the analytical investigations were performed at the Center for Chemical Polymer Technology CPT, which was supported by the European Commission and the federal state of North Rhine-Westphalia (No. 300088302). The authors wish to thank Dr. K. Rahimi, S. Rieder, and M. Maassen for the STEM/cryoTEM analysis and M. Merklinger for MFP synthesis. The authors acknowledge the use of XPS (J. Roes) and FTIR (B. Becker). Publisher Copyright: Copyright © 2020 American Chemical Society.

PY - 2020/4

Y1 - 2020/4

N2 - We here performed an in-depth investigation of the behavior of microgels (mu gels) and their associated physicochemical transformations under shear force. Thermo- and mechanoresponsive poly(N-vinylcaprolactam) (PVCL) mu gels (d similar to 400 nm) cross-linked with a force-responsive mechanofluorophore in different crosslinking 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 mu gels 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 mu gels rapidly lose their corona and the cores agglomerate altering mu gel functionality. Surprisingly, mu gels 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 mu gel solutions as well as circulation within the bloodstream of living organisms.

AB - We here performed an in-depth investigation of the behavior of microgels (mu gels) and their associated physicochemical transformations under shear force. Thermo- and mechanoresponsive poly(N-vinylcaprolactam) (PVCL) mu gels (d similar to 400 nm) cross-linked with a force-responsive mechanofluorophore in different crosslinking 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 mu gels 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 mu gels rapidly lose their corona and the cores agglomerate altering mu gel functionality. Surprisingly, mu gels 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 mu gel solutions as well as circulation within the bloodstream of living organisms.

KW - microgels

KW - mechanical properties

KW - shear force

KW - mechanochemistry

KW - colloids

KW - RHEOLOGICAL PROPERTIES

KW - INTERNAL STRUCTURE

KW - MACROMOLECULES

KW - TEMPERATURE

KW - SUSPENSIONS

KW - DENSITY

U2 - 10.1021/acsapm.0c00111

DO - 10.1021/acsapm.0c00111

M3 - Article

SN - 2637-6105

VL - 2

SP - 1682

EP - 1691

JO - ACS Applied Polymer Materials

JF - ACS Applied Polymer Materials

IS - 4

ER -