https://nova.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:55190 Wed 24 Apr 2024 12:59:00 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:33530 Wed 14 Nov 2018 16:20:31 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:54214 Tue 13 Feb 2024 12:01:51 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:43868 Tue 04 Oct 2022 12:28:47 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:36046 Thu 30 Jan 2020 14:07:08 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:50504 Thu 27 Jul 2023 12:56:38 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:51175 Thu 24 Aug 2023 14:33:18 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:41045 Thu 21 Jul 2022 14:42:22 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:29256 a. Furthermore, the simulations reveal that the addition of a single Flory-Huggins interaction parameter analogous to the hydrophilicity of the counterion is sufficient to replicate the observed specific anion response of a hydrophobic weak polyelectrolyte brush.]]> Sat 24 Mar 2018 07:39:15 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:51979 Mon 13 Nov 2023 08:48:07 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:51170 Mon 13 Nov 2023 08:46:57 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:33531 Fri 28 Jun 2019 11:32:06 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:29257 Fri 28 Jun 2019 11:25:07 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:39206 N-isopropylacrylamide) (PNIPAM) brushes is investigated as a function of confining stress and system temperature using neutron reflectometry (NR), numerical self-consistent field theory, and the reanalysis of colloid probe atomic force microscopy (AFM) data from the literature. For NR experiments, confinement is achieved using a custom-made sample environment, and the corresponding reflectometry data are analyzed using a novel “distribution model.” The NR and AFM experiments probe similar temperature–stress combinations and generally find qualitative agreement, with some variations highlighting path-dependent (isostress vs isothermal, respectively) behavior. All techniques indicate that confinement removes the critical transition point in the thermoresponse of PNIPAM and results in the brush assuming a block-like volume fraction profile with a uniform internal structure. The PNIPAM brushes recover from such treatment, regaining their thermoresponse upon resolvation. Understanding the structure of responsive polymer brushes under confinement is essential, as brush applications are often accompanied by a surface-normal force (i.e., lubrication) and brush properties are dependent on their structure.]]> Fri 27 May 2022 09:52:26 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:42233 3COO, causes collapse) and thiocyanate (KSCN, causes swelling), two ions at opposite ends of the Hofmeister series, has been monitored with neutron reflectometry (NR) and quartz crystal microbalance with dissipation (QCM-D). These techniques revealed that the balance of the swelling/collapse influence of the two ions on the structure of the brush is temperature dependent. At low temperatures in mixed salt environments, the influence of the acetate and thiocyanate ions appears additive, antagonistic and approximately equal in magnitude, with brush thickness and dissipation similar to the brush in the absence of electrolyte. At higher temperatures, the influence of the acetate ion diminishes, resulting in an increase in the relative influence of the thiocyanate ion on the brush conformation. These temperature dependent specific ion effects are attributed to increased steric crowding in the brush, along with an increased affinity of the thiocyanate ion for the polymer at higher temperatures.]]> Fri 19 Aug 2022 11:42:19 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:44487 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.]]> Fri 14 Oct 2022 08:57:26 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:50202 Fri 07 Jul 2023 09:49:26 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:42771 2MA) and poly(2-(diethylamino)ethyl methacrylate) (PDEA), as well as a P(MEO₂MA-co-DEA) copolymer brush of 90:10 mol% composition has been examined. PMEO₂MA is a thermoresponsive polymer with a lower critical solution temperature of ~28 °C, PDEA a weak polybase with an apparent pK_a of ~7.5, while the copolymer brush exhibits both pH and temperature responsive behaviour. Brushes were synthesised using surface initiated ARGET ATRP. The effect of temperature at low and high pH in the presence of different electrolytes on the thickness of the P(MEO₂MA-co-DEA) 90:10 mol% brush was tracked with ellipsometry and the polymer volume fraction profile was elucidated with neutron reflectometry. The effect of each electrolyte on the copolymer brush conformation as the temperature changes could be switched by changing the pH from low (charged DEA segments) to high (uncharged DEA segments). The overall behaviour of the copolymer in each salt was PDEA-like at low pH, and MEO₂MA-like at high pH. At low pH a reverse Hofmeister effect was observed, while at high pH a direct Hofmeister effect was observed.]]> Fri 02 Sep 2022 10:32:17 AEST ]]>