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Interaction Forces on Polyampholytic Hydrogel Gradient Surfaces
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Kagaku Analys AB, Göteborg, Sweden.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Susos AG, Dübendorf, Switzerland.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Insplorion AB, Göteborg, Sweden.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. MariboHilleshög Research AB, Landskrona, Sweden.
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2019 (English)In: ACS Omega, ISSN 2470-1343, Vol. 4, no 3, p. 5670-5681Article in journal (Refereed) Published
Abstract [en]

Rational design and informed development of nontoxic antifouling coatings requires a thorough understanding of the interactions between surfaces and fouling species. With more complex antifouling materials, such as composites or zwitterionic polymers, there follows also a need for better characterization of the materials as such. To further the understanding of the antifouling properties of charge-balanced polymers, we explore the properties of layered polyelectrolytes and their interactions with charged surfaces. These polymers were prepared via self-initiated photografting and photopolymerization (SIPGP); on top of a uniform bottom layer of anionic poly(methacrylic acid) (PMAA), a cationic poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) thickness gradient was formed. Infrared microscopy and imaging spectroscopic ellipsometry were used to characterize chemical composition and swelling of the combined layer. Direct force measurements by colloidal probe atomic force microscopy were performed to investigate the forces between the polymer gradients and charged probes. The swelling of PMAA and PDMAEMA are very different, with steric and electrostatic forces varying in a nontrivial manner along the gradient. The gradients can be tuned to form a protein-resistant charge-neutral region, and we demonstrate that this region, where both electrostatic and steric forces are small, is highly compressed and the origin of the protein resistance of this region is most likely an effect of strong hydration of charged residues at the surface, rather than swelling or bulk hydration of the polymer. In the highly swollen regions far from charge-neutrality, steric forces dominate the interactions between the probe and the polymer. In these regions, the SIPGP polymer has qualitative similarities with brushes, but we were unable to quantitatively describe the polymer as a brush, supporting previous data suggesting that these polymers are cross-linked.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019. Vol. 4, no 3, p. 5670-5681
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-156495DOI: 10.1021/acsomega.9b00339ISI: 000462921900124PubMedID: 31459721Scopus ID: 2-s2.0-85063358089OAI: oai:DiVA.org:liu-156495DiVA, id: diva2:1306646
Note

Funding agencies: European Commissions Sixth Framework Program Integrated Project AMBIO (Advanced Nanostructured Surfaces for the Control of Biofouling) [NMP-CT-2005-011827]; European Communitys Seventh Framework Program [237997]; Swedish Government Strategic Research Area

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-09-09Bibliographically approved
In thesis
1. Surface characterization and manipulation of polyampholytic hydrogel coatings
Open this publication in new window or tab >>Surface characterization and manipulation of polyampholytic hydrogel coatings
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is dedicated to building up fundamental knowledge about polyampholytic hydrogels, which are developed in our group for anti-fouling purposes. Charge-balanced polymers, where positive and negative charges balance each other, have emerged as interesting candidates for many applications in materials science. We have prepared charge-balanced materials by forming thickness gradients of oppositely charged polyelectrolytes, and use these as model systems for a systematic investigation of the materials and their responses to environmental changes. These hydrogel gradients were sequentially grafted from substrates via surface-initiated photografting and photopolymerization (SIPGP) of cationic and anionic polyelectrolytes. At some thickness ratios, these form a charge-balanced system where the net surface charge is zero, and with certain similarity to zwitterionic systems. The surface charge of the hydrogels is the principal parameter regulating non-specific protein adsorption, and among other things, we demonstrate that the position of the fouling-resistant charge-neutral region can be manipulated upon pH changes. The chemical compositions of the hydrogel gradients were characterized by microscopic infrared spectroscopy. Optical analysis by spectroscopic ellipsometry and imaging surface plasmon resonance were used to monitor the swelling of the hydrogel films, and protein adsorption onto these in real-time. Surface forces, i.e. the interactions with the hydrogels from an intermolecular perspective, which are related mainly to electrostatic and steric forces, were probed by direct force measurement using atomic force microscopy. Force curves were used to determine the surface charge distribution over the hydrogels, and to indicate the correlation between surface charge and protein adsorption. In the later work, hydrogel gradients were patterned as arrayed spots. Their thicknesses and surface roughness provide further information about the polymer structure and provides a basis for relating ellipsometric swelling profiles to thicknesses as obtained by atomic force microscopy. Finally, it is demonstrated how charged hydrogel films can be used as spacers to tune the optimum distance between silver nanoparticles and fluorophores for metal-enhanced fluorescence (MEF). The aim of this work is to understand polyampholytic hydrogels from various perspectives: surface charges and their distribution, the polymer structure, and surface interactions. The knowledge and experience obtained contribute to the general understanding of zwitterionic materials, and to the development of anti-fouling coatings, optical sensing platforms and other applications of charge-balanced hydrogels.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. p. 74
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1987
Keywords
Hydrogels, antifouling, charge-balanced material, polyampholytes, force measurements, polymer swelling, protein adsorption, patterning, plasmonics
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:liu:diva-156496 (URN)10.3384/diss.diva-156496 (DOI)9789176850831 (ISBN)
Public defence
2019-05-17, Planck, Fysikhuset, Campus Valla, Linköping, 10:00 (English)
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Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-29Bibliographically approved

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Tai, Feng-iAndersson, OlofEkblad, TobiasEderth, Thomas

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