Related Experiment Video
Updated: Jun 1, 2026
13:57
Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes
Published on: December 24, 2014
Polymer-brush lubricated surfaces with colloidal inclusions under shear inversion
L Spirin1, A Galuschko, T Kreer
1Institute of Physics, Johannes Gutenberg-University, Mainz, Germany.
Physical Review Letters
|May 24, 2011
Summary
Compressed polymer-brush bilayers show shear stress overshoots with simple solvents but not dry brushes. Adding colloidal particles controls mechanical instabilities, enabling characteristic response times determination.
Area of Science:
- Polymer physics
- Soft matter science
- Materials science
Background:
- Polymer brushes are versatile materials with applications in coatings, biomaterials, and nanotechnology.
- Understanding their response to external stimuli, like shear and compression, is crucial for designing advanced materials.
- Nonstationary processes, where conditions change rapidly, present unique challenges in predicting material behavior.
Purpose of the Study:
- To investigate the mechanical response of compressed, sheared polymer-brush bilayers containing colloidal inclusions under nonstationary inversion processes.
- To elucidate the role of solvent and colloidal particle properties in dictating the system's behavior.
- To develop a scaling approach for predicting characteristic response times.
Main Methods:
- Molecular dynamics simulations were employed to model the polymer-brush bilayers.
- Scaling theory was applied to analyze the simulation data and theoretical predictions.
- Systems with simple (dimeric) solvents and dry brushes were compared.
- Varying softness of colloidal inclusions was systematically studied.
Main Results:
- Polymer-brush bilayers with simple solvents exhibited a distinct overshoot in shear stress during inversion.
- Dry brushes (without explicit solvent molecules) failed to show this shear stress overshoot.
- The inclusion of macromolecular structures, specifically colloids of varying softness, was shown to effectively control mechanical instabilities.
- A scaling approach was proposed to determine characteristic times for conformational and collective responses.
Conclusions:
- The presence of solvent is critical for observing shear stress overshoots in compressed, sheared polymer-brush bilayers.
- Colloidal inclusions offer a mechanism to tune and control the mechanical instabilities of polymer brushes.
- The developed scaling approach provides a framework for predicting the dynamic response of such complex soft matter systems.
More Related Videos
Related Concept Videos
01:17Colloids and Suspensions
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...
01:09Colloidal precipitates
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
03:22Colloids
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
01:23Design Example: Deciding Thickness of Lubricating Fluid in a Shaft
Effective lubrication between a rotating shaft and its bearing housing is essential in rotating machinery to minimize friction, wear, and energy loss. With carefully controlled thickness and viscosity, the lubricant layer prevents metal-to-metal contact, ensuring smooth operation.
To calculate the required thickness of the lubricant layer, the tangential velocity at the shaft's surface must first be determined. This velocity is calculated by converting the rotational speed to angular velocity...
To calculate the required thickness of the lubricant layer, the tangential velocity at the shaft's surface must first be determined. This velocity is calculated by converting the rotational speed to angular velocity...