Alignment Layer of Liquid Crystal Using Plant-Based Isoeugenol-Substituted Polystyrene

Area of Science:

• Polymer Chemistry
• Materials Science
• Liquid Crystal Displays

Background:

• Liquid crystal (LC) alignment layers are crucial for display performance.
• Developing sustainable and eco-friendly alignment materials is an ongoing challenge.
• Plant-derived monomers offer a renewable alternative to traditional petrochemical-based polymers.

Purpose of the Study:

• To synthesize and characterize novel isoeugenol-substituted polystyrenes.
• To investigate the liquid crystal (LC) alignment behavior of these plant-based polymers.
• To evaluate the stability and potential applications of these materials as LC alignment layers.

Main Methods:

• Polymer modification reactions were used to create isoeugenol-substituted polystyrenes (PIEU#).
• The molar content of isoeugenol moiety was varied (100, 80, 60, 40, 20%).
• LC cells were fabricated using the synthesized polymer films, and their alignment behavior and stability were assessed.

Main Results:

• Higher molar content of isoeugenol side groups generally led to vertical LC alignment.
• Vertical alignment correlated with lower polar surface energy (< 3.59 mJ/m²), attributed to the nonpolar isoeugenol groups.
• Excellent alignment stability was observed for PIEU100 at 100 °C and under UV irradiation (15 J/cm²).

Conclusions:

• Renewable isoeugenol-based polymers can effectively induce vertical LC alignment.
• These materials present a viable eco-friendly alternative for LC alignment systems.
• The synthesized polymers demonstrate good thermal and photochemical stability for practical applications.