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Astier S, Johnson EC, Norvilaite O, Varlas S, Brotherton EE, Sanderson G, Leggett GJ, Armes SP. Controlling Adsorption of Diblock Copolymer Nanoparticles onto an Aldehyde-Functionalized Hydrophilic Polymer Brush via pH Modulation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024. [PMID: 38320303 PMCID: PMC10883040 DOI: 10.1021/acs.langmuir.3c03392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2024]
Abstract
Sterically stabilized diblock copolymer nanoparticles with a well-defined spherical morphology and tunable diameter were prepared by RAFT aqueous emulsion polymerization of benzyl methacrylate at 70 °C. The steric stabilizer precursor used for these syntheses contained pendent cis-diol groups, which means that such nanoparticles can react with a suitable aldehyde-functional surface via acetal bond formation. This principle is examined herein by growing an aldehyde-functionalized polymer brush from a planar silicon wafer and studying the extent of nanoparticle adsorption onto this model substrate from aqueous solution at 25 °C using a quartz crystal microbalance (QCM). The adsorbed amount, Γ, depends on both the nanoparticle diameter and the solution pH, with minimal adsorption observed at pH 7 or 10 and substantial adsorption achieved at pH 4. Variable-temperature QCM studies provide strong evidence for chemical adsorption, while scanning electron microscopy images recorded for the nanoparticle-coated brush surface after drying indicate mean surface coverages of up to 62%. This fundamental study extends our understanding of the chemical adsorption of nanoparticles on soft substrates.
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Affiliation(s)
- Samuel Astier
- Department of Chemistry, The University of Sheffield, Dainton Building, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K
| | - Edwin C Johnson
- Department of Chemistry, The University of Sheffield, Dainton Building, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K
| | - Oleta Norvilaite
- Department of Chemistry, The University of Sheffield, Dainton Building, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K
| | - Spyridon Varlas
- Department of Chemistry, The University of Sheffield, Dainton Building, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K
| | - Emma E Brotherton
- Department of Chemistry, The University of Sheffield, Dainton Building, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K
| | - George Sanderson
- GEO Specialty Chemicals, Hythe, Southampton, Hampshire SO45 3ZG, U.K
| | - Graham J Leggett
- Department of Chemistry, The University of Sheffield, Dainton Building, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K
| | - Steven P Armes
- Department of Chemistry, The University of Sheffield, Dainton Building, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K
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Robertson H, Gresham IJ, Nelson ARJ, Gregory KP, Johnson EC, Willott JD, Prescott SW, Webber GB, Wanless EJ. Solvent-Modulated Specific Ion Effects: Poly( N-isopropylacrylamide) Brushes in Nonaqueous Electrolytes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:335-347. [PMID: 38117209 PMCID: PMC10910595 DOI: 10.1021/acs.langmuir.3c02596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 12/04/2023] [Accepted: 12/08/2023] [Indexed: 12/21/2023]
Abstract
Pertinent to cryopreservation as well as energy storage and batteries, nonaqueous electrolytes and their mixtures with water were investigated. In particular, specific ion-induced effects on the modulation of a poly(N-isopropylacrylamide) (PNIPAM) brush were investigated in various dimethyl sulfoxide (DMSO)-water solvent mixtures. Spectroscopic ellipsometry and neutron reflectometry were employed to probe changes in brush swelling and structure, respectively. In water-rich solvents (i.e., pure water and 6 mol % DMSO), PNIPAM undergoes a swollen to collapsed thermotransition with increasing temperature, whereby a forward Hofmeister series was noted; K+ and Li+ electrolytes composed of SCN- and I- salted-in (stabilized) PNIPAM chains, and electrolytes of Cl- and Br- salted-out (destabilized) the polymer. The cation was seen to play a lesser role than that of the anion, merely modulating the magnitude of the anion effect. In 70 mol % DMSO, a collapsed to swollen thermotransition was noted for PNIPAM. Here, concentration-dependent specific ion effects were observed; a forward series was observed in 0.2 mol % electrolytes, whereas increasing the electrolyte concentration to 0.9 mol % led to a series reversal. While no thermotransition was observed in pure DMSO, a solvent-induced specific ion series reversal was noted; SCN- destabilized the brush and Cl- stabilized the brush. Both series reversals are attributed to the delicate balance of interactions between the solvent, solute (ion), and substrate (brush). Namely, the stability of the solvent clusters was hypothesized to drive polymer solvation.
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Affiliation(s)
- Hayden Robertson
- College
of Science, Engineering and Environment, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Isaac J. Gresham
- School
of Chemistry, University of Sydney, Sydney 2052, Australia
| | - Andrew R. J. Nelson
- Australian
Centre for Neutron Scattering, ANSTO, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Kasimir P. Gregory
- Division
of Biomedical Science and Biochemistry, Research School of Biology, The Australian National University, Canberra, Australian Capital
Territory 0200, Australia
| | - Edwin C. Johnson
- Department
of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
| | - Joshua D. Willott
- College
of Science, Engineering and Environment, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Stuart W. Prescott
- School of
Chemical Engineering, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Grant B. Webber
- College
of Science, Engineering and Environment, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Erica J. Wanless
- College
of Science, Engineering and Environment, University of Newcastle, Callaghan, New South Wales 2308, Australia
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