Interactions between Polyelectrolyte Brushes and Hofmeister Ions: Chaotropes versus Kosmotropes

Kou, Ran; Zhang, Jian; Wang, Tao; Liu, Guangming

doi:10.1021/acs.langmuir.5b02698

Cited by 89 publications

(128 citation statements)

References 59 publications

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“…The reduction in thickness of the brush in KI indicates that it is salted, which occurs at salt concentrations in excess of that of the counter-ions [56]. The anion dependence of the thickness is consistent with the results of a study of Hofmeister ions on a strong polycation [57].…”

Section: Brush Thicknesssupporting

confidence: 85%

Salt Dependence of the Tribological Properties of a Surface-Grafted Weak Polycation in Aqueous Solution

et al. 2017

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The nanoscopic adhesive and frictional behaviour of end-grafted poly[2-(dimethyl amino)ethyl methacrylate] (PDMAEMA) films (brushes) in contact with gold-or PDMAEMA-coated atomic force microscope tips in potassium halide solutions with different concentrations up to 300 mM is a strong function of salt concentration. The conformation of the polymers in the brush layer is sensitive to salt concentration, which leads to large changes in adhesive forces and the contact mechanics at the tip-sample contact, with swollen brushes (which occur at low salt concentrations) yielding large areas of contact and friction-load plots that fit JKR behaviour, while collapsed brushes (which occur at high salt concentrations) yield sliding dominated by ploughing, with conformations in between fitting DMT mechanics. The relative effect of the different anions follows the Hofmeister series, with I − collapsing the brushes more than Br − and Cl − for the same salt concentration.

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Section: Brush Thicknesssupporting

confidence: 85%

Salt Dependence of the Tribological Properties of a Surface-Grafted Weak Polycation in Aqueous Solution

et al. 2017

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“…It is known that the frequency shift (Δf) reflects a mass change of the polyelectrolyte brushes induced by the hydration/dehydration of the brushes ,. In Figure , it is evident that the Δf of the PMETAC brushes exhibits distinct changes with the salt concentration in the presence of different types of counterions.…”

Section: Resultsmentioning

confidence: 99%

“…In Figure , the dissipation shift (ΔD) of the PMETAC brushes also exhibits distinct changes with the salt concentration in the presence of different types of counterions. ΔD is generally related to the conformation of the polymer brushes and the friction between the polymer brushes and the surrounding water molecules ,,. In the presence of ClO 4 − , ΔD sharply decreases as the salt concentration increases from 0 to 5×10 −5 M, and then gradually decreases with the increase in salt concentration from 5×10 −5 to 5×10 −3 M. As the salt concentration increases further from 5×10 −3 to 0.5 M, no obvious changes in ΔD are observed.…”

Section: Resultsmentioning

confidence: 99%

“…At the high salt concentrations, the polyelectrolyte brushes collapse and dehydrate with increasing salt concentration due to the reduction in osmotic pressure within the brushes . In our previous work, we have found that the ion‐specific interactions between the positively charged polyelectrolyte brushes and the chaotropic anions are dominated by the direct specific ion‐pairing interactions between the anions and the positively charged quaternary ammonium groups, whereas the ion‐specific interactions between the brushes and the kosmotropic anions are dominated by the competition for water molecules between the anions and the brushes. Moreover, the polyelectrolyte brushes collapse and dehydrate with increasing salt concentration from 1×10 −3 to 0.5 M for all the types of counterions due to the decreased osmotic pressure within the brushes .…”

Section: Introductionmentioning

confidence: 96%

“…In our previous work, we have found that the ion‐specific interactions between the positively charged polyelectrolyte brushes and the chaotropic anions are dominated by the direct specific ion‐pairing interactions between the anions and the positively charged quaternary ammonium groups, whereas the ion‐specific interactions between the brushes and the kosmotropic anions are dominated by the competition for water molecules between the anions and the brushes. Moreover, the polyelectrolyte brushes collapse and dehydrate with increasing salt concentration from 1×10 −3 to 0.5 M for all the types of counterions due to the decreased osmotic pressure within the brushes . However, we demonstrate here that the addition of chaotrope‐type counterions can induce obvious dehydration and collapse of the polyelectrolyte brushes in the low salt concentration regime, whereas the addition of kosmotrope‐type counterions can induce an increase in hydration associated with a swelling of the polyelectrolyte brushes in the low salt concentration regime.…”

Section: Introductionmentioning

confidence: 98%

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Counterion Specificity of Polyelectrolyte Brushes: Role of Specific Ion‐Pairing Interactions

2018

Self Cite

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We demonstrate here that the properties of poly (2-(methacryloyloxy) ethyl trimethylammonium chloride) brushes can be tuned by counterion species. When the brushes are exposed to external chloride (Cl ) counterions, obvious dehydration and collapse are only observed at high salt concentrations. In the presence of very strongly chaotropic perchlorate (ClO ), the brushes strongly dehydrate and collapse at a very low salt concentration. For the strongly chaotropic thiocyanate ion (SCN ), the changes in hydration and conformation of the brushes are similar to those observed for ClO but at a smaller extent at very low salt concentrations. With the addition of kosmotropic acetate (Ac ), hydration of the brushes increases, accompanied by a swelling of the brushes in the low-salt-concentration regime. In contrast, the brushes dehydrate and collapse with increasing concentration of Ac in the high-salt-concentration regime. The counterion specificity of the brushes demonstrated here is determined by specific ion-pairing interactions through modulating the osmotic pressure within the brushes and the hydrophobicity of the ion pairs.

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Pyroelectric Polyelectrolyte Brushes

Wang,

Hu,

Sant

et al. 2024

Advanced Materials

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Piezo‐ and pyroelectric materials are of interest, for example, for energy harvesting applications, for the development of tactile sensors, as well as neuromorphic computing. This study reports the observation of pyro‐ and piezoelectricity in thin surface‐attached polymer brushes containing zwitterionic and electrolytic side groups that are prepared via surface‐initiated polymerization. The pyro‐ and piezoelectric properties of the surface‐grafted polyelectrolyte brushes are found to sensitively depend on and can be tuned by variation of the counterion. The observed piezo‐ and pyroelectric properties reflect the structural complexity of polymer brushes, and are attributed to a complex interplay of the non‐uniform segment density within these films, together with a non‐uniform distribution of counterions and specific ion effects. The fabrication of thin pyroelectric films by surface‐initiated polymerization is an important addition to the existing strategies towards such materials. Surface‐initiated polymerization, in particular, allows for facile grafting of polar thin polymer films from a wide range of substrates via a straightforward two‐step protocol that obviates the need for multistep laborious synthetic procedures or thin film deposition protocols. The ability to produce polymer brushes with piezo‐ and pyroelectric properties opens up new avenues of application of these materials, for example, in energy harvesting or biosensing.This article is protected by copyright. All rights reserved

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Interactions between Polyelectrolyte Brushes and Hofmeister Ions: Chaotropes versus Kosmotropes

Cited by 89 publications

References 59 publications

Salt Dependence of the Tribological Properties of a Surface-Grafted Weak Polycation in Aqueous Solution

Salt Dependence of the Tribological Properties of a Surface-Grafted Weak Polycation in Aqueous Solution

Counterion Specificity of Polyelectrolyte Brushes: Role of Specific Ion‐Pairing Interactions

Pyroelectric Polyelectrolyte Brushes

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