Triclinic Liquid Crystal of Counter-Rotating Squashed Double Helices in a Side-Chain Polymer

Area of Science:

• Materials Science
• Crystallography
• Polymer Chemistry

Background:

• Liquid crystals exhibit ordered phases between solid and liquid states.
• Chiral liquid crystals display unique optical and structural properties.
• Polysiloxanes are versatile polymers with tunable properties.

Purpose of the Study:

• To synthesize and characterize a novel polysiloxane-based liquid crystal.
• To investigate the self-assembly behavior and resulting supramolecular structures.
• To determine the crystallographic symmetry and helical arrangements.

Main Methods:

• Synthesis of polysiloxane with tris-alkoxy-ended mesogenic side groups.
• X-ray diffraction studies to determine crystal structure and symmetry.
• Differential scanning calorimetry to analyze phase transitions.

Main Results:

• Formation of an unusual low-symmetry antiferrochiral liquid crystal (space group P1̅).
• The structure consists of distorted left- and right-handed double-helices with alternating splay and twist.
• A metastable orthorhombic structure (space group Fddd) with 8 double helices per unit cell was observed upon faster cooling.

Conclusions:

• The study reveals a new type of antiferrochiral liquid crystal with complex helical structures.
• The observed low symmetry and helical arrangements offer insights into molecular self-assembly.
• The discovery of a metastable phase highlights the influence of cooling rates on liquid crystal structures.