Hierarchical Nanostructures and Self-Assemblies in Smectic-Nematic Liquid Crystalline Diblock Copolymers

Area of Science:

• Polymer Science
• Materials Science
• Liquid Crystals

Background:

• Liquid crystalline (LC) diblock copolymers offer unique self-assembly properties.
• Controlling nanoscale hierarchical structures is crucial for advanced materials.
• Understanding the interplay between LC order and polymer architecture is key.

Purpose of the Study:

• To investigate the self-assembly behavior of flexible LC diblock copolymers with varying molecular weights.
• To explore the coexistence of smectic and nematic orders in 3D hierarchical structures.
• To demonstrate the ability to fine-tune complex nanostructures.

Main Methods:

• Sequential anionic polymerization to synthesize diblock copolymers of different molecular weights but similar compositions.
• Characterization of nanophase separated structures and LC ordering.
• Analysis of order-order transitions (OOT) and structural stability.

Main Results:

• Observation of coexisting smectic and nematic orders in 3D bicontineous cubic or hexagonal structures.
• Higher MW copolymer shows an order-order transition from lamellae to hexagonal-packed cylinders upon nematic ordering.
• Lower MW copolymer forms a stable gyroid structure with nanoscale LC defects.

Conclusions:

• The delicate balance of LC interactions and geometric frustration dictates the observed complex structures.
• This novel class of copolymers provides a pathway to precisely control 2D and 3D nanostructures with sub-10 nm features.
• The findings open avenues for designing advanced materials with tailored hierarchical architectures.