Intradomain phase transitions in flexible block copolymers with self-aligning segments

Area of Science:

• Polymer Science
• Soft Matter Physics
• Materials Science

Background:

• Flexible block copolymers (BCPs) exhibit complex self-assembly behaviors.
• Understanding orientational order of polymer segments is crucial for BCP properties.
• Existing theories often simplify or neglect inter-segment interactions.

Purpose of the Study:

• To develop and analyze a generalized self-consistent field theory for flexible BCPs incorporating orientational order.
• To investigate the emergence of complex segment order parameters within BCP domains.
• To predict novel phase behaviors and transitions driven by segment alignment.

Main Methods:

• Generalization of self-consistent field theory (SCFT) for flexible BCPs.
• Inclusion of Landau-de Gennes free energy for polar/nematic order parameters.
• Numerical solution using a pseudo-spectral approach.
• Analysis of chain conformation statistics and self-consistent torque.

Main Results:

• Emergence of spatially complex segment order parameters (director fields) within lamellar domains.
• Non-linear dependence of BCP thermodynamics on segregation (χN) and alignment enthalpy (ε).
• Prediction of new lamellar phases with coexisting alignment regions and broken symmetries.
• Demonstration of increased transition thresholds due to elastic costs (Frank elasticity).

Conclusions:

• The model successfully captures complex intra-domain orientational ordering in BCPs.
• Segment alignment significantly influences BCP phase behavior and domain stability.
• New BCP phases with broken symmetries are predicted, expanding the landscape of self-assembled materials.