Letter to the Editor: Friction between Surfaces—Polyacrylic Acid Brush and Silica—Mediated by Calcium Ions

Dunér, Gunnar; Thormann, Esben; Ramström, Olof; Dédinaité, Andra

doi:10.1080/01932691.2010.511973

Cited by 24 publications

(27 citation statements)

References 18 publications

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“…End‐grafted polyelectrolytes (PEs) have found increasing applications as highly engineered stimuli‐responsive surfaces with applications which include wettability control, friction reduction, protein immobilization, transport control, and nanosensors . The so called stimuli‐responsiveness of these systems originates from the inherent capacity for ion‐exchange with the environment and specifically the interplay between ionic charges of the polymer and resulting changes in physical morphology .…”

Section: Introductionmentioning

confidence: 99%

“…Poly(acrylic acid) (PAA) is a weak PE that has been widely studied as a brush material in solution conditions due to its simple chemical structure and straightforward chemical synthesis . PAA brushes are attractive as smart coatings due to its pH responsiveness (pKa ∼ 4.5), high hydrophilicity, low fouling character, lubrication or friction reduction, and ionic strength sensitivity …”

Section: Introductionmentioning

confidence: 99%

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Planar Phase Separation of Weak Polyelectrolyte Brushes in Poor Solvent

Gao¹,

Kearney²,

Howarter³

2017

J Polym Sci B Polym Phys

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Poly(acrylic acid) (PAA) brushes were synthesized on silicon wafer substrates using a silane linker and Z-group RAFT method, which enables the controlled variation of brush characteristics. Atomic force microscopy (AFM) was used to characterize the brush morphology in the dry state, which ranged from isolated globules to micelles to a continuous film featuring dimples. Surface morphology was primarily determined by total grafted polymer concentration with a critical polymer concentration between 4.5 and 6.5 3 10 223 mol/nm 2 , where the polymer rich regions transition from micellar islands to a continuous film with dimples. However, even at the highest grafting densities and brush strand lengths used in this study, a flat homogenous film was not formed. Morphological consequences of the solvent and thermal history were shown to persist into poorly solvated state after being dried. X-ray photoelectron spectroscopy (XPS) was used to quantify the degree of remaining salt after drying. It was found that a higher relative amount of salt was retained after drying in the lower grafting density samples.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Planar Phase Separation of Weak Polyelectrolyte Brushes in Poor Solvent

Gao¹,

Kearney²,

Howarter³

2017

J Polym Sci B Polym Phys

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“…30 One PAA-coated surface and a bare silica surface were utilized in their AFM colloidal probe friction studies, and they found very low friction forces in the absence of calcium ions and at low pH in the presence of 10 mM CaCl 2 . However, increasing the pH to 7.5, which facilitates electrostatic interactions between the divalent cation and carboxylate groups on the polymer, resulted in high friction even though no attractive surface force was present.…”

Section: Breakage and Reformation Of Attractive Intralayer Physical Bmentioning

confidence: 99%

Synergies in lubrication

Dédinaité

Claesson

2017

Phys. Chem. Chem. Phys.

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To slide surfaces against each other with application of a minimum force and minimum wear has been important since ancient times, and it remains equally important today. The use of oil-soluble lubricants is widely spread in technology, whereas living organisms have developed water-soluble lubricants to facilitate sliding motions. In this perspective article we focus on water-based lubrication in the boundary lubrication regime, and particularly lubrication synergies. This focus has, of course, found inspiration from the outstanding lubrication properties of synovial joints. It has ignited significant amount of research, mostly aimed at answering the question: Which molecule is the magic biolubricant? Different research groups have advocated different answers, and the debate has been intensive. In this article we argue that the question in itself is inappropriate. The relevant question is rather the following: How do molecules work in synergy to provide superior lubrication?

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“…Dursch et al 49 characterized DD_1 with regards to solute-partitioning, and demonstrated the hydrogel characteristics of the lens surface, as well as showing that the gel layer has a negative charge at neutral pH. The increase in CoF after ageing could be a consequence of electrostatic adsorption of proteins, or an increased crosslink density of the hydrogel due to association of divalent cations present in the lubricant -similar to what was observed by Dunér et al 54 for poly (acrylic acid) polymer brushes in the presence of calcium. Certain lenses had an increase in CoF after prolonged exposure to TLF.…”

Section: Discussionmentioning

confidence: 55%