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Johnson EC, Varlas S, Norvilaite O, Neal TJ, Brotherton EE, Sanderson G, Leggett GJ, Armes SP. Adsorption of Aldehyde-Functional Diblock Copolymer Spheres onto Surface-Grafted Polymer Brushes via Dynamic Covalent Chemistry Enables Friction Modification. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2023; 35:6109-6122. [PMID: 37576584 PMCID: PMC10413866 DOI: 10.1021/acs.chemmater.3c01227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 07/05/2023] [Indexed: 08/15/2023]
Abstract
Dynamic covalent chemistry has been exploited to prepare numerous examples of adaptable polymeric materials that exhibit unique properties. Herein, the chemical adsorption of aldehyde-functional diblock copolymer spherical nanoparticles onto amine-functionalized surface-grafted polymer brushes via dynamic Schiff base chemistry is demonstrated. Initially, a series of cis-diol-functional sterically-stabilized spheres of 30-250 nm diameter were prepared via reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization. The pendent cis-diol groups within the steric stabilizer chains of these precursor nanoparticles were then oxidized using sodium periodate to produce the corresponding aldehyde-functional spheres. Similarly, hydrophilic cis-diol-functionalized methacrylic brushes grafted from a planar silicon surface using activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) were selectively oxidized to generate the corresponding aldehyde-functional brushes. Ellipsometry and X-ray photoelectron spectroscopy were used to confirm brush oxidation, while scanning electron microscopy studies demonstrated that the nanoparticles did not adsorb onto a cis-diol-functional precursor brush. Subsequently, the aldehyde-functional brushes were treated with excess small-molecule diamine, and the resulting imine linkages were converted into secondary amine bonds via reductive amination. The resulting primary amine-functionalized brushes formed multiple dynamic imine bonds with the aldehyde-functional diblock copolymer spheres, leading to a mean surface coverage of approximately 0.33 on the upper brush layer surface, regardless of the nanoparticle size. Friction force microscopy studies of the resulting nanoparticle-decorated brushes enabled calculation of friction coefficients, which were compared to that measured for the bare aldehyde-functional brush. Friction coefficients were reasonably consistent across all surfaces except when particle size was comparable to the size of the probe tip. In this case, differences were ascribed to an increase in contact area between the tip and the brush-nanoparticle layer. This new model system enhances our understanding of nanoparticle adsorption onto hydrophilic brush layers.
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Affiliation(s)
- Edwin C. Johnson
- Department
of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
| | - Spyridon Varlas
- Department
of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
| | - Oleta Norvilaite
- Department
of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
| | - Thomas J. Neal
- Department
of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
| | - Emma E. Brotherton
- Department
of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
| | | | - Graham J. Leggett
- Department
of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
| | - Steven P. Armes
- Department
of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
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Flemming P, Münch AS, Fery A, Uhlmann P. Constrained thermoresponsive polymers - new insights into fundamentals and applications. Beilstein J Org Chem 2021; 17:2123-2163. [PMID: 34476018 PMCID: PMC8381851 DOI: 10.3762/bjoc.17.138] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 08/10/2021] [Indexed: 12/15/2022] Open
Abstract
In the last decades, numerous stimuli-responsive polymers have been developed and investigated regarding their switching properties. In particular, thermoresponsive polymers, which form a miscibility gap with the ambient solvent with a lower or upper critical demixing point depending on the temperature, have been intensively studied in solution. For the application of such polymers in novel sensors, drug delivery systems or as multifunctional coatings, they typically have to be transferred into specific arrangements, such as micelles, polymer films or grafted nanoparticles. However, it turns out that the thermodynamic concept for the phase transition of free polymer chains fails, when thermoresponsive polymers are assembled into such sterically confined architectures. Whereas many published studies focus on synthetic aspects as well as individual applications of thermoresponsive polymers, the underlying structure-property relationships governing the thermoresponse of sterically constrained assemblies, are still poorly understood. Furthermore, the clear majority of publications deals with polymers that exhibit a lower critical solution temperature (LCST) behavior, with PNIPAAM as their main representative. In contrast, for polymer arrangements with an upper critical solution temperature (UCST), there is only limited knowledge about preparation, application and precise physical understanding of the phase transition. This review article provides an overview about the current knowledge of thermoresponsive polymers with limited mobility focusing on UCST behavior and the possibilities for influencing their thermoresponsive switching characteristics. It comprises star polymers, micelles as well as polymer chains grafted to flat substrates and particulate inorganic surfaces. The elaboration of the physicochemical interplay between the architecture of the polymer assembly and the resulting thermoresponsive switching behavior will be in the foreground of this consideration.
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Affiliation(s)
- Patricia Flemming
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
- Technische Universität Dresden, 01062 Dresden, Germany
| | - Alexander S Münch
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
| | - Andreas Fery
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
- Technische Universität Dresden, 01062 Dresden, Germany
| | - Petra Uhlmann
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
- University of Nebraska-Lincoln, NE 68588, Lincoln, USA
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Johnson L, Gray DM, Niezabitowska E, McDonald TO. Multi-stimuli-responsive aggregation of nanoparticles driven by the manipulation of colloidal stability. NANOSCALE 2021; 13:7879-7896. [PMID: 33881098 DOI: 10.1039/d1nr01190a] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The capacity to control the dispersed or aggregated state of colloidal particles is particularly attractive for facilitating a diverse range of smart applications. For this reason, stimuli-responsive nanoparticles have garnered much attention in recent years. Colloidal systems that exhibit multi-stimuli-responsive behaviour are particularly interesting materials due to the greater spatial and temporal control they display in terms of dispersion/aggregation status; such behaviour can be exploited for implant formation, easy separation of a previously dispersed material or for the blocking of unwanted pores. This review will provide an overview of the recent publications regarding multi-stimuli-responsive microgels and hybrid core-shell nanoparticles. These polymer-based nanoparticles are highly sensitive to environmental conditions and can form aggregated clusters due to a loss of colloidal stability, triggered by temperature, pH and ionic strength stimuli. We aim to provide the reader with a discussion of the recent developments in this area, as well as an understanding of the fundamental concepts which underpin the responsive behaviour, and an exploration of their applications.
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Affiliation(s)
- Luke Johnson
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, UK.
| | - Dominic M Gray
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, UK.
| | - Edyta Niezabitowska
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, UK.
| | - Tom O McDonald
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, UK.
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Gresham IJ, Humphreys BA, Willott JD, Johnson EC, Murdoch TJ, Webber GB, Wanless EJ, Nelson ARJ, Prescott SW. Geometrical Confinement Modulates the Thermoresponse of a Poly( N-isopropylacrylamide) Brush. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02775] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Isaac J. Gresham
- School of Chemical Engineering, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Ben A. Humphreys
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | - Joshua D. Willott
- Membrane Science and Technology, Mesa+ Institute for Nanotechnology, University of Twente, Enschede 7500 AE, The Netherlands
| | - Edwin C. Johnson
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | - Timothy J. Murdoch
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | - Grant B. Webber
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | - Erica J. Wanless
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | | | - Stuart W. Prescott
- School of Chemical Engineering, UNSW Sydney, Sydney, New South Wales 2052, Australia
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Johnson EC, Gresham IJ, Prescott SW, Nelson A, Wanless EJ, Webber GB. The direction of influence of specific ion effects on a pH and temperature responsive copolymer brush is dependent on polymer charge. POLYMER 2021. [DOI: 10.1016/j.polymer.2020.123287] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Johnson EC, Willott JD, Gresham IJ, Murdoch TJ, Humphreys BA, Prescott SW, Nelson A, de Vos WM, Webber GB, Wanless EJ. Enrichment of Charged Monomers Explains Non-monotonic Polymer Volume Fraction Profiles of Multi-stimulus Responsive Copolymer Brushes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:12460-12472. [PMID: 33105998 DOI: 10.1021/acs.langmuir.0c01502] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Multi-stimulus responsive poly(2-(2-methoxyethoxy)ethyl methacrylate-co-2-(diethylamino)ethyl methacrylate) [P(MEO2MA-co-DEA)] 80:20 mol % copolymer brushes were synthesized on planar silica substrates via surface-initiated activators continuously regenerated via electron transfer atom transfer radical polymerization. Brush thickness was sensitive to changes in pH and temperature as monitored with ellipsometry. At low pH, the brush is charged and swollen, while at high pH, the brush is uncharged and more collapsed. Clear thermoresponsive behavior is also observed with the brush more swollen at low temperatures compared to high temperatures at both high and low pH. Neutron reflectometry was used to determine the polymer volume fraction profiles (VFPs) at various pH values and temperatures. A region of lower polymer content, or a depletion region, near the substrate is present in all of the experimental polymer VFPs, and it is more pronounced at low pH (high charge) and less so at high pH (low charge). Polymer VFPs calculated through numerical self-consistent field theory suggest that enrichment of DEA monomers near the substrate results in the experimentally observed non-monotonic VFPs. Adsorption of DEA monomers to the substrate prior to initiation of polymerization could give rise to DEA segment-enriched region proximal to the substrate.
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Affiliation(s)
- Edwin C Johnson
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Joshua D Willott
- Membrane Surface Science (MSuS), Membrane Science and Technology cluster, Mesa+ Institute for Nanotechnology, University of Twente, Enschede 7500 AE, The Netherlands
| | - Isaac J Gresham
- School of Chemical Engineering, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Timothy J Murdoch
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Ben A Humphreys
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Stuart W Prescott
- School of Chemical Engineering, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Andrew Nelson
- ANSTO, Locked bag 2001, Kirrawee DC, Sydney, New South Wales 2232, Australia
| | - Wiebe M de Vos
- Membrane Surface Science (MSuS), Membrane Science and Technology cluster, Mesa+ Institute for Nanotechnology, University of Twente, Enschede 7500 AE, The Netherlands
| | - Grant B Webber
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Erica J Wanless
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan, New South Wales 2308, Australia
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