Transition Behavior of Polyelectrolyte Brushes Depending on Polymer Chain Density

Hayashi, Shujiro; Abe, Takashi; Higashi, Nobuyuki; Niwa, Masazo; Kurihara, Kazue

doi:10.1080/10587250108024758

Cited by 2 publications

(7 citation statements)

References 8 publications

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“…76 If the transition of the state exists, then it should influence other properties of polyelectrolyte brushes. Indeed, we found the density-dependent jump in the transfer ratio and the surface potential of the brushes, 77 establishing the existence of the density (interchain distance)-dependent transition of polyelectrolytes in solutions.…”

Section: ■ Studies Of Molecular Architecturesupporting

confidence: 62%

Molecular Architecture Studied by the Surface Forces Measurement

Kurihara

2016

Langmuir

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This feature article reviews the surface forces measurement as a tool for studying molecular architecture chemistry. The history of the measurement is briefly described in the Introduction. The general overview covers specific features of the surface forces measurement as a tool for studying and using molecular architecture. This measurement is powerful for understanding interaction forces and for characterizing and discovering the phenomena at solid-liquid interfaces and soft complex matter. An apparatus for opaque samples was developed, which can be used to study not only opaque samples in various media but also electrochemical processes under various electrochemical potentials. Our studies of molecular architecture are reviewed; they include biological molecular recognition especially involved in the enzyme-substrate interaction; polyelectrolyte brushes exhibiting steric repulsion, which can be reproduced by the osmotic pressure of the counterions, and a density-dependent transition; the hydrogen-bonded molecular macrocluster formation of alcohol and carboxylic acids adsorbed on silica in nonpolar solvents such as cyclohexane; and surface forces between ferrocene-modified electrodes under various applied potentials. These studies demonstrate how the forces measurement is used to identify interacting species such as in biological systems to reveal unknown phenomena and to characterize soft complex matter and the effective potential of the electrodes. Readers will be introduced to the broad applications of the force measurement.

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Section: ■ Studies Of Molecular Architecturesupporting

confidence: 62%

Molecular Architecture Studied by the Surface Forces Measurement

Kurihara

2016

Langmuir

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“…It corresponds to the stress for deformation of the polymer layers in water upon compression. The effective layer thickness before deformation ( D 0 ) was obtained by extrapolation of the stress curves to zero stress when P was plotted in the form of a P − D plot, or from the deflection point of a log P − D plot. , Both analyses provided an identical value for D 0 within experimental error. At a separation distance very close to D 0 , a small jump-in of ca.…”

Section: Methodsmentioning

confidence: 99%

“…It is possible to simplify the complexities of (three-dimensional) polyelectrolyte solutions using two-dimensionally organized brush layers of polyelectrolytes. This approach has been both theoretically − and experimentally − adopted to study polyelectrolytes . One may stress that the importance of the polyelectrolyte brushes is not limited in fundamental aspects: it extends to many technological applications such as colloidal stabilization, adhesion, and a motif of novel molecular self-assemblies at interfaces that could provide unique functions …”

Section: Introductionmentioning

confidence: 99%

“…Recently, several groups including us experimentally measured the thickness of variously prepared brush layers of polyelectrolytes, using surface forces, − small angle neutron scattering, and surface X-ray reflectivity 15-17 measurements.…”

Section: Introductionmentioning

confidence: 99%

“…Swelling of the brushes at a higher ionization of polyelectrolytes and in the presence of a salt (NaBr) was qualitatively studied 11a,b It was also possible to determine the surface potential of the layer and compare it with the ionization degree of constituent polyelectrolytes 11c. The knowledge of these parameters is essential for understanding the properties of the brush layers but is difficult to obtain by other methods.…”

Section: Introductionmentioning

confidence: 99%

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Polyelectrolyte Brush Layers Studied by Surface Forces Measurement: Dependence on pH and Salt Concentrations and Scaling

et al. 2002

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Interactions between opposed brush layers of polyelectrolytes ionized poly(L-glutamic acid) (PLGA) or poly(L-lysine) (PLL) in water were directly investigated using surface forces measurement. The brush layers were prepared by the Langmuir-Blodgett deposition of amphiphiles bearing PLGA (degree of polymerization n ) 21, 44, and 48) or PLL (n ) 41 and 52) as hydrophilic groups. The density of polyelectrolyte chains was around 0.4 chain/nm 2 . Surface force profiles, consisting of a long-range electrical double layer repulsion and a short-range steric repulsion, were measured and analyzed with varying pH, salt concentration, and polyelectrolyte chain length. The surface potential obtained from the double layer repulsion indicated that nearly all of the ionized groups in the brush layers were neutralized by counterions. In the case of PLGA, the steric repulsion of the brush layer increased with increasing pH from 9 to 10, reflecting the increase in the ionization degree of the carboxylic groups, and then decreased above pH 10 due to salt effect. Similar behavior was also observed for PLL: the steric repulsion increased when the pH was changed from 4 to 3 and decreased at pH 2. In the cases of both PLGA and PLL, the steric repulsion decreased with increasing salt concentration (0.43-10 mM) at a fixed pH, which was likely due to a decrease in the osmotic pressure of the counterions. The distance at which the steric repulsion appeared (D0) corresponded to twice the length of an extended polyelectrolyte molecule. This distance D0 remained practically the same under the pH and salt conditions studied for the brush of an identical polymerization degree. Twice the length of polyelectrolyte chains L0 was defined as D0 -6 (nm), where 6 nm was twice the length of the long alkyl chains in polyelectrolyte amphiphiles, and was found to be proportional to the polymerization degree of polyelectrolyte n. The stress profiles, obtained by differentiating the force profiles, were scaled according to the distance to provide identical profiles for different polymer chain lengths. An equation describing the stress profiles was derived based on a model that attributed the steric force to the osmotic pressure of the counterions. The equation reproduced well the stress profiles of PLGA and PLL brushes, where the osmotic coefficient was a variable parameter. The osmotic coefficient was estimated to be 0.004 for both PLGA and PLL and much less than the value determined in solution (∼0.2), indicating that the counterions bound more strongly to the polyelectrolytes in the brush layer than to isolated polyelectrolytes in solution. The advantage of characterizing polyelectrolytes by surface forces measurement was discussed.

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Transition Behavior of Polyelectrolyte Brushes Depending on Polymer Chain Density

Cited by 2 publications

References 8 publications

Molecular Architecture Studied by the Surface Forces Measurement

Molecular Architecture Studied by the Surface Forces Measurement

Polyelectrolyte Brush Layers Studied by Surface Forces Measurement: Dependence on pH and Salt Concentrations and Scaling

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