Related Experiment Video
Updated: Aug 8, 2026
06:26
Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
Structural forces near phase transitions of liquid crystals
1J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
Summary
Researchers measured forces between objects in liquid crystals (LCs) near phase transitions. Findings align with Landau-de Gennes theory, revealing nanoscale forces and adsorbed molecular layer properties.
Area of Science:
- Physics
- Materials Science
Background:
- Liquid crystal (LC) phases influence forces between immersed bodies.
- Understanding these forces is crucial for nanoscale applications.
Purpose of the Study:
- To measure liquid-crystalline structural forces near phase transitions.
- To validate Landau-de Gennes theory at the nanoscale.
- To characterize adsorbed molecular layers on surfaces.
Main Methods:
- Utilized an atomic force microscope (AFM) with precise temperature control.
- Measured forces between bodies immersed in liquid crystals.
- Analyzed data near LC phase transition temperatures.
Main Results:
- Observed forces closely matched Landau-de Gennes phenomenological theory predictions.
- Demonstrated agreement even at nanoscale interaction lengths.
- Identified and characterized an adsorbed molecular layer, determining its thickness and elastic properties.
Conclusions:
- Landau-de Gennes theory accurately describes nanoscale LC forces.
- Precise temperature control enables detailed study of LC phase behavior.
- Adsorbed molecular layers possess measurable thickness and elastic characteristics.
Related Concept Videos
02:31Phase Transitions
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to occupy...
02:39Phase Transitions: Melting and Freezing
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
02:33Phase Transitions: Sublimation and Deposition
Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and standard pressure, a piece of dry ice (solid CO2) sublimes, appearing to gradually disappear without ever forming any liquid. Snow and ice sublimate at temperatures below the melting point of water, a slow process that may be accelerated by winds and the reduced atmospheric pressures at high altitudes. When solid iodine is warmed, the solid sublimes...
02:39Phase Diagrams
A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. These diagrams indicate the physical states that exist under specific conditions of pressure and temperature and also provide the pressure dependence of the phase-transition temperatures (melting points, sublimation points, boiling points). Regions or areas labeled solid, liquid, and gas represent single phases, while lines or curves represent...
01:19Phase Diagram
The phase of a given substance depends on the pressure and temperature. Thus, plots of pressure versus temperature showing the phase in each region provide considerable insights into the thermal properties of substances. Such plots are known as phase diagrams. For instance, in the phase diagram for water (Figure 1), the solid curve boundaries between the phases indicate phase transitions (i.e., temperatures and pressures at which the phases coexist).
01:21Phase Transitions
A phase transition is the process in which a substance changes from one state of matter to another, like from a solid to a liquid, liquid to gas, or vice versa, at a specific temperature and under given pressure conditions. This change is spontaneous and is affected by alterations in temperature and pressure. These parameters impact the strength of the forces between molecules (intermolecular forces) in the substance.During a phase transition, both the initial and final phases of the substance...