Optical microscopy study for director patterns around disclinations in side-chain liquid crystalline polymer films

Area of Science:

• Materials Science
• Polymer Science
• Liquid Crystals

Background:

• Disclinations in liquid crystalline polymer films exhibit complex director fields.
• Understanding these structures is crucial for controlling material properties.

Purpose of the Study:

• To investigate director fields around disclinations in side-chain liquid crystalline polymer films.
• To analyze the instability and patterns of disclinations with varying film thickness.

Main Methods:

• Polarizing optical microscopy was used to observe director fields.
• Analysis of optical black brushes and stripes around disclinations.

Main Results:

• Observed radial, spiral, circular, and hyperbolic director patterns for integer disclinations (s = +1, s = -1).
• Identified specific configurations of (+1, -1) disclinations during annihilation.
• Found that increasing film thickness causes disclination instability, splitting s = +/-1 brushes into s = +/-1/2 brushes.

Conclusions:

• The study reveals novel director patterns and the instability of disclinations in liquid crystalline polymer films.
• Theoretical analysis explains the observed disclination instability and pattern transitions.