Specific Anion Effects on the Internal Structure of a Poly(<i>N</i>-isopropylacrylamide) Brush

Murdoch, Timothy J.; Humphreys, Ben A.; Willott, Joshua D.; Gregory, Kasimir P.; Prescott, Stuart W.; Nelson, Andrew; Wanless, Erica J.

doi:10.1021/acs.macromol.6b01001

Cited by 57 publications

(136 citation statements)

References 69 publications

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Section: The Effect Of Specific Anions (Scn − and Ch 3 Co −mentioning

confidence: 99%

“…2 ) on the equilibrium thermoresponse of PNIPAAm brushes was studied using in situ ellipsometry, quartz crystal QCM-D, static contact angle measurements, neutron reflectometry (NR), and AFM [31,32]. It was found that the shift in transition temperature was in line with the Hofmeister series where transition temperature was shifted to lower temperature by kosmotropic acetate ions and higher temperature by chaotropic thiocyanate ions [31,32]. Koenig et al studied the effect of NaCl salt on the thermoresponsive behavior of PNIPAAm brushes using QCM and ellipsometry and found that transition temperature was shifted to lower temperatures by the addition of NaCl salt due to the interaction of the ions with the amide groups and the hindrance of hydrogen-bonding formation [33].…”

Section: The Effect Of Specific Anions (Scn − and Ch 3 Co −mentioning

confidence: 99%

“…Besides temperature and pH, the salt-induced swelling behavior of PNIPAAm brushes and thin gel films was studied by several research groups [17,22,[28][29][30][31][32][33]. Ishida et al studied the NA 2 SO 4 salt-induced changes in grafted PNIPAAm layers using quartz crystal microbalance (QCM-D) with dissipation and AFM and used high salt concentrations in the range of 0.1 to 1 M [29].…”

Section: Introductionmentioning

confidence: 99%

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Optical characterization of salt-induced swelling behavior ofpoly(N-isopropylacrylamide) terpolymer hydrogel layers

Anac¹,

Bozdoğan²

2019

Turk J Chem

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This study reports for the first time the effect of different sodium halide salts (NaClO 4 , NaI, and Na 2 CO 3) in the low concentration range (in the range of 10 −7-1 M) on the swelling behavior of photo-crosslinked, surfaceimmobilized poly(N-isopropyl acrylamide) (PNIPAAm) terpolymer layers. PNIPAAm terpolymer (consisting of Nisopropylacrylamide, methacrylic acid, and 4-methacryloxybenzophenone) was synthesized via free radical polymerization. The PNIPAAm terpolymer layers were prepared on gold substrates via spin coating and crosslinked and surface attached via UV radiation. The swelling behavior of the layers in monovalent (NaClO 4 and NaI) and divalent (Na 2 CO 3) solutions was monitored by surface plasmon/optical waveguide spectroscopy. The terpolymer layers did not swell significantly at very low salt concentrations (10 −7-10 −5 M), whereas an increase in swelling upon the addition of salt up to 10 −2-0.1 M depending on the salt was observed. Further increase in the salt concentration up to 1 M led to collapse of the terpolymer PNIPAAm layers due to the reduction in solvent quality of the salt solution. The full collapse of the terpolymer PNIPAAm layers with 1 M salt solution was observed only when divalent kosmotropic Na 2 CO 3 salt was used.

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Section: The Effect Of Specific Anions (Scn − and Ch 3 Co −mentioning

confidence: 99%

Section: The Effect Of Specific Anions (Scn − and Ch 3 Co −mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical characterization of salt-induced swelling behavior ofpoly(N-isopropylacrylamide) terpolymer hydrogel layers

Anac¹,

Bozdoğan²

2019

Turk J Chem

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“…PNIPAM brushes exhibit lower critical solution temperature (LCST) type behavior, undergoing a swollen to collapsed transition as the temperature increases above 32 C. Previous studies of PNIPAM brushes have observed a diffuse layer at low temperatures, which transitions through a two-phase swollen-collapsed state as the system temperature passes through its LCST at 32 C, before collapsing entirely above 32 C (Murdoch et al, 2016;Yim et al, 2004;. The PNIPAM system was chosen as it is well characterized and allows for a range of system conformations to be investigated for a single substrate and solvent combination.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the robustness of the neutron reflectometry technique for structural characterization of polymer brushes

et al. 2021

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Neutron reflectometry is the foremost technique for in situ determination of the volume fraction profiles of polymer brushes at planar interfaces. However, the subtle features in the reflectometry data produced by these diffuse interfaces challenge data interpretation. Historically, data analyses have used least-squares approaches that do not adequately quantify the uncertainty of the modeled profile and ignore the possibility of other structures that also match the collected data (multimodality). Here, a Bayesian statistical approach is used that permits the structural uncertainty and multimodality to be quantified for polymer brush systems. A free-form model is used to describe the volume fraction profile, minimizing assumptions regarding brush structure, while only allowing physically reasonable profiles to be produced. The model allows the total volume of polymer and the profile monotonicity to be constrained. The rigor of the approach is demonstrated via a round-trip analysis of a simulated system, before it is applied to real data examining the well characterized collapse of a thermoresponsive brush. It is shown that, while failure to constrain the interfacial volume and consider multimodality may result in erroneous structures being derived, carefully constraining the model allows for robust determination of polymer brush compositional profiles. This work highlights that an appropriate combination of flexibility and constraint must be used with polymer brush systems to ensure the veracity of the analysis. The code used in this analysis is provided, enabling the reproduction of the results and the application of the method to similar problems.

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“…The properties of brushes are substantially determined by the polymer type, the length of the polymer chains, their grafting density, and the interactions between polymer chains and environment. Therefore, polymer brushes are widely used to tune the surface properties of materials and to render them, for example, superhydrophobic, highly hydrophilic, cell‐adhesive, antifouling, and other properties . They are also able to demonstrate switchable properties due to the stimuli‐responsive behavior of the polymer chains that were grafted onto the surface .…”

Section: Introductionmentioning

confidence: 99%

Effect of Architecture of Thermoresponsive Copolymer Brushes on Switching of Their Adsorption Properties

Marschelke

Puretskiy

Raguzin

et al. 2019

Macro Chemistry & Physics

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Herein, the effect of architecture of stimuli‐responsive polymer brushes on the switching of colloidal particle adsorption is reported. Thermoresponsive copolymer brushes containing positively charged amino groups are used and investigated how negatively charged colloidal particles electrostatically adsorb onto them. The distribution of charged groups (block or random copolymer architecture) and the conformation of the polymer chains (extended or collapsed state) are varied. It is found that the strongest adsorption is achieved at high fractions of charged groups in the brushes, while the amount of adsorbed particles is independent of the polymer chain conformation; that is, the adsorption of particles cannot be switched. On the contrary to this, the most pronounced switching of adsorption is achieved at low fractions of charged/adhesive groups in the brushes when the adsorption of particles is weak. The lowest fraction of charged/adhesive groups (one group per few polymer chains) can be exclusively achieved by random copolymerization and not by block copolymers. An explanation of the adsorption behavior of colloidal particles on switchable brushes is proposed.

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Specific Anion Effects on the Internal Structure of a Poly(N-isopropylacrylamide) Brush

Cited by 57 publications

References 69 publications

Optical characterization of salt-induced swelling behavior ofpoly(N-isopropylacrylamide) terpolymer hydrogel layers

Optical characterization of salt-induced swelling behavior ofpoly(N-isopropylacrylamide) terpolymer hydrogel layers

Quantifying the robustness of the neutron reflectometry technique for structural characterization of polymer brushes

Effect of Architecture of Thermoresponsive Copolymer Brushes on Switching of Their Adsorption Properties

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