Related Experiment Video
Updated: Jan 20, 2026
10:25
Isolation and Quantitative Evaluation of Brush Cells from Mouse Tracheas
Published on: June 12, 2019
7.7K
Brush-sheathed particles diffusing at brush-coated surfaces in the thermally responsive PNIPAAm system.
Huilin Tu1, Liang Hong, Stephen M Anthony
1Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|January 31, 2007
Summary
Near-surface diffusion of polymer-coated microspheres is slower than bulk diffusion below 32°C. Above this temperature, diffusion increases, suggesting reduced hydrodynamic coupling and potential electrostatic repulsion effects.
Area of Science:
- Surface Science
- Polymer Chemistry
- Colloid Science
Background:
- Poly(N-isopropylacrylamide) (PNIPAAm) exhibits a lower critical solution temperature (LCST) around 32°C.
- Polymer brushes influence particle-surface interactions and dynamics.
- Understanding near-surface diffusion is crucial for applications involving confined colloids.
Purpose of the Study:
- To investigate the near-surface translational diffusion of PNIPAAm brush-functionalized silica microspheres.
- To compare near-surface diffusion with bulk diffusion across the PNIPAAm LCST.
- To elucidate the factors affecting diffusion dynamics near a polymer-coated surface.
Main Methods:
- Phase-contrast microscopy and particle tracking algorithms were employed.
- Sedimentation of silica microspheres onto polymer-coated substrates was studied.
- Dynamic light scattering was used to measure bulk diffusion coefficients.
Main Results:
- Near-surface diffusion coefficient (D(surface)) was approximately 0.6 times the bulk diffusion coefficient (D(bulk)) below 32°C.
- D(surface)/D(bulk) ratio increased to 0.8-0.9 above 32°C.
- A small negative surface charge (zeta potential = -6 mV) prevented particle adhesion.
Conclusions:
- Near-surface diffusion is significantly influenced by temperature relative to the PNIPAAm LCST.
- Enhanced diffusion above the LCST suggests reduced hydrodynamic coupling to the surface.
- Electrostatic repulsion may play a role in mediating diffusion changes above the LCST.
More Related Videos
Related Concept Videos
01:12Diffusion
216.5K
Diffusion is the passive movement of substances down their concentration gradients—requiring no expenditure of cellular energy. Substances, such as molecules or ions, diffuse from an area of high concentration to an area of low concentration in the cytosol or across membranes. Eventually, the concentration will even out, with the substance moving randomly but causing no net change in concentration. Such a state is called dynamic equilibrium, which is essential for maintaining overall...
216.5K
01:21Diffusion
6.2K
Diffusion is a type of passive transport. In passive transport, a substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across the space. For example, take the diffusion of substances through the air. When someone opens a perfume bottle in a room filled with people, the perfume is at its highest concentration in the bottle and is at its lowest at the edges of the room. The perfume vapor will diffuse, or spread away, from the...
6.2K
01:16Response Surface Methodology
612
Response Surface Methodology (RSM) is a collection of statistical and mathematical techniques used to develop, improve, and optimize processes. It is particularly valuable when many input variables or factors potentially influence a response variable.
The process of RSM involves several key steps:
The process of RSM involves several key steps:
612
01:23Factors Affecting Dissolution: Particle Size and Effective Surface Area
1.6K
Dissolution kinetics, an essential aspect of oral drug delivery, is significantly influenced by the drug's particle size. According to the Noyes-Whitney dissolution model, the dissolution rate correlates directly with the drug's surface area. The larger the surface area, the higher the drug's solubility in water, leading to a faster drug dissolution rate. Reducing particle size increases the effective surface area, enhancing the dissolution process. Micronization and nanosizing are...
1.6K
03:48Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion
31.2K
Although gaseous molecules travel at tremendous speeds (hundreds of meters per second), they collide with other gaseous molecules and travel in many different directions before reaching the desired target. At room temperature, a gaseous molecule will experience billions of collisions per second. The mean free path is the average distance a molecule travels between collisions. The mean free path increases with decreasing pressure; in general, the mean free path for a gaseous molecule will be...
31.2K
01:27Thermal expansion and Thermal stress: Problem Solving
2.1K
San Francisco's Golden Gate Bridge is exposed to temperatures ranging from -15 °C to 40 °C. At its coldest, the main span of the bridge is 1275 m long. Assuming that the bridge is made entirely of steel, what is the change in its length between these temperatures?
To solve the problem, first, identify the known and unknown quantities. The initial length (L) of the bridge is 1275 m, the coefficient of linear expansion (α) for steel is 12 x 10-6/°C, and the change in temperature (ΔT) is 55...
To solve the problem, first, identify the known and unknown quantities. The initial length (L) of the bridge is 1275 m, the coefficient of linear expansion (α) for steel is 12 x 10-6/°C, and the change in temperature (ΔT) is 55...
2.1K