Perforated layer structures in liquid crystalline rod-coil block copolymers.

Area of Science:

• Polymer Science
• Materials Science
• Crystallography

Background:

• Rod-coil block copolymers (BCPs) exhibit unique self-assembly behaviors.
• Liquid crystalline block copolymers combine properties of both polymer chains and liquid crystals.
• Understanding BCP morphology is crucial for designing advanced materials.

Purpose of the Study:

• To investigate the self-assembly and structural characteristics of novel rod-coil liquid crystalline BCPs.
• To identify and characterize the formation of perforated layer structures in poly(styrene-block-(2,5-bis[4-methoxyphenyl]oxycarbonyl)styrene) (PS-b-PMPCS).
• To explore the influence of molecular weight and composition on the observed morphologies.

Main Methods:

• Differential scanning calorimetry (DSC) for thermal analysis.
• Polarized light microscopy (PLM) for visual observation of structures.
• Small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) for structural analysis.
• Transmission electron microscopy (TEM) for real-space imaging of morphologies.

Main Results:

• A novel tetragonal perforated layer structure was observed in PS-b-PMPCS.
• The formation of this structure was dependent on molecular weight, appearing at different compositions for low and high M(w) samples.
• The perforation symmetry was identified as tetragonal, deviating from typical hexagonal packing.
• The 'onset' of perforation was visualized, showing initial stages of structure formation.
• Blending with polystyrene (PS) homopolymer induced uniform tetragonal perforations at specific compositions.

Conclusions:

• The rod-coil nature of the BCP significantly influences phase boundary shifts and resulting morphologies.
• Tetragonal perforated layers represent a novel structural motif in liquid crystalline BCPs.
• Compositional control, including blending, offers a pathway to tailor BCP nanostructures for advanced applications.