ORCID Profile
0000-0003-1870-755X
Current Organisations
University of Twente
,
University of Newcastle Australia
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Publisher: American Chemical Society (ACS)
Date: 23-02-2021
Publisher: Elsevier BV
Date: 2017
Publisher: American Chemical Society (ACS)
Date: 18-09-2012
DOI: 10.1021/MZ3003566
Abstract: Brush-modified silica hybrids have been synthesized by growing poly(2-(diethylamino)ethyl methacrylate) (poly(DEA)) brushes on 120 nm diameter silica particles by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP). This is the first report of using SI-ARGET ATRP to synthesize poly(DEA) brushes. The kinetics of poly(DEA) brush growth in 4:1 v/v ethanol/water was monitored. The hydrodynamic diameter of the resulting brush-modified particles was dependent on the solution pH due to the weak polybasic nature of the brushes. Below the p
Publisher: Wiley
Date: 18-11-2019
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 05-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5CP07468A
Abstract: Specific anion identity and concentration dictates the direction and magnitude of the shift in LCST for a pNIPAM brush determined by in situ ellipsometry, QCM-D and static contact angle measurements.
Publisher: American Chemical Society (ACS)
Date: 05-08-2016
Publisher: American Chemical Society (ACS)
Date: 18-11-2020
Publisher: American Chemical Society (ACS)
Date: 06-2020
Publisher: American Chemical Society (ACS)
Date: 29-10-2020
Publisher: American Chemical Society (ACS)
Date: 06-03-2020
Publisher: American Chemical Society (ACS)
Date: 14-10-2020
Publisher: American Chemical Society (ACS)
Date: 03-12-2019
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Chemical Society (ACS)
Date: 07-05-2013
DOI: 10.1021/LA4004092
Abstract: Coatings consisting of polymer brushes are an effective way to modify solid interfaces. Polymer brush-modified hybrid particles have been prepared by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) of 2-(diethylamino)ethyl methacrylate (DEA) on silica particles. We have optimized the synthesis with respect to changing the reducing agent, temperature, and reaction solvent from an aqueous ethanol mixture to an aqueous methanol mixture. Our flexible electrostatically adsorbed macroinitiator approach allows for the modification of a variety of surfaces. Polybasic brushes have been grown on silica particles of different sizes, from 120 to 840 nm in diameter, as well as on wafers, and a comparison of the products has allowed the effect of surface curvature to be elucidated. An examination of the thickness of the dry brush and the aqueous hydrodynamic brush at both pH 7 and at 4 demonstrated that growth increased substantially with substrate curvature for particles with a diameter below 450 nm. This is attributed to the increasing separation between active chain ends, reducing the rate of termination. This is believed to be the first time that this effect has been demonstrated experimentally. Furthermore, we have seen that polymer brush growth on planar wafers was significantly reduced when the reaction mixture was stirred.
Publisher: Wiley
Date: 19-07-2018
DOI: 10.1002/MAR.21131
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP02206D
Abstract: Hypersaline environments are ubiquitous in nature and are found in myriad technological processes. Recent empirical studies have revealed a significant discrepancy between the predicted and observed screening lengths at high...
Publisher: American Chemical Society (ACS)
Date: 04-03-2016
Publisher: American Chemical Society (ACS)
Date: 20-01-2019
Publisher: American Chemical Society (ACS)
Date: 13-12-2016
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.JCIS.2016.11.044
Abstract: The thermoresponse of poly(di(ethyleneglycol) methyl ether methacrylate) (PMEO
Publisher: American Chemical Society (ACS)
Date: 23-03-2015
DOI: 10.1021/ACS.LANGMUIR.5B00116
Abstract: The anion-specific solvation and conformational behavior of weakly basic poly(2-dimethylamino)ethyl methacrylate (poly(DMA)), poly(2-diethylamino)ethyl methacrylate (poly(DEA)), and poly(2-diisopropylamino)ethyl methacrylate (poly(DPA)) brushes, with correspondingly increasing inherent hydrophobicity, have been investigated using in situ ellipsometric and quartz crystal microbalance with dissipation (QCM-D) measurements. In the osmotic brush regime, as the initial low concentration of salt is increased, the brushes osmotically swell by the uptake of solvent as they become charged and the attractive hydrophobic inter- and intrachain interactions are overcome. With increased ionic strength, the brushes move into the salted brush regime where they desolvate and collapse as their electrostatic charge is screened. Here, as the brushes collapse, they transition to more uniform and rigid conformations, which dissipate less energy, than similarly solvated brushes at lower ionic strength. Significantly, in these distinct regimes brush behavior is not only ionic strength dependent but is also influenced by the nature of the added salt based on its position in the well-known Hofmeister or lyotropic series, with potassium acetate, nitrate, and thiocyanate investigated. The strongly kosmotropic acetate anions display low affinity for the hydrophobic polymers, and largely unscreened electrosteric repulsions allow the brushes to remain highly solvated at higher acetate concentrations. The mildly chaotropic nitrate and strongly chaotropic thiocyanate anions exhibit a polymer hydrophobicity-dependent affinity for the brushes. Increasing thiocyanate concentration causes the brushes to collapse at lower ionic strength than for the other two anions. This study of weak polybasic brushes demonstrates the importance of all ion, solvent, and polymer interactions.
Publisher: American Chemical Society (ACS)
Date: 25-09-2020
Publisher: American Chemical Society (ACS)
Date: 04-05-2020
Publisher: American Chemical Society (ACS)
Date: 17-01-2018
Publisher: American Chemical Society (ACS)
Date: 11-01-2022
Publisher: American Chemical Society (ACS)
Date: 10-02-2014
DOI: 10.1021/LA4047275
Abstract: The swelling behavior of poly(2-(diethylamino)ethyl methacrylate) (PDEA) brushes in response to changes in solution pH and ionic strength has been investigated. The brushes were synthesized by ARGET ATRP methodology at the silica-aqueous solution interface via two different surface-bound initiator approaches: electrostatically adsorbed cationic macroinitiator and covalently anchored silane-based ATRP initiator moieties. The pH-response of these brushes is studied as a function of the solvated brush thickness in a constant flow regime that elucidates the intrinsic behavior of polymer brushes. In situ ellipsometry equilibrium measurements show the pH-induced brush swelling and collapse transitions are hysteretic in nature. Furthermore, high temporal resolution kinetic studies demonstrate that protonation and solvent ingress during swelling occur much faster than the brush charge neutralization and solvent expulsion during collapse. This hysteresis is attributed to the formation of a dense outer region or skin during collapse that retards solvent egress. Moreover, at a constant pH below its pKa, the PDEA brush exhibited a critical conformational change in the range 0.5-1 mM electrolyte, a range much narrower than predicted by the theory of the osmotic brush regime. This behavior is attributed to the hydrophobicity of the collapsed brush. The swelling and collapse kinetics for this salt-induced transition are nearly identical. This is in contrast to the asymmetry in the rate of the pH-induced response, suggesting an alternative mechanism for the two processes dependent on the nature of the environmental trigger.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4CP05292G
Abstract: Monomer hydrophobicity dominates the kinetics of the pH-response of tertiary amine methacrylate brushes as determined by in situ ellipsometry and QCM-D kinetic and equilibrium measurements.
Publisher: American Chemical Society (ACS)
Date: 18-06-2021
No related grants have been discovered for Joshua Willott.