Wettability of Nematic Liquid Crystals

Area of Science:

• Materials Science
• Physical Chemistry
• Soft Matter Physics

Background:

• Organic liquids, specifically nematic liquid crystals, are expected to wet high surface energy solids such as mica.
• However, experimental observations show that wetting often does not occur, presenting a contradiction to theoretical expectations.

Purpose of the Study:

• To develop a theoretical model explaining the non-wetting behavior of nematic liquid crystals on high surface energy solids.
• To identify the physical mechanisms responsible for the observed wetting phenomena.

Main Methods:

• A theoretical model was developed incorporating Hamaker forces (representing surface energy affinity) and elastic effects arising from nematic order.
• The model predicts the contact angles and film formation behavior of these liquids on solid substrates.

Main Results:

• The model successfully predicts that nematic liquid crystals exhibit small contact angles on high surface energy solids.
• The results also correctly predict the formation of ultrathin liquid films preceding the main bulk drops.
• The study identifies elastic effects due to nematic order as the key factor opposing wetting.

Conclusions:

• The interplay between attractive forces (Hamaker) and repulsive elastic forces dictates the wetting behavior of nematic liquid crystals.
• The proposed model provides a framework for understanding and predicting liquid crystal-solid interactions, particularly concerning wetting phenomena.