Bicontinuous Microemulsions in Partially Charged Ternary Polymer Blends

Area of Science:

• Polymer science
• Materials science
• Physical chemistry

Background:

• Understanding polymer blend phase behavior is crucial for designing advanced materials.
• Charged polymer systems present unique challenges due to electrostatic interactions.
• Previous studies often show phase separation in charged blends, limiting complex morphologies.

Purpose of the Study:

• To investigate the phase behavior of a partially charged ternary polymer blend.
• To determine the conditions under which complex morphologies like bicontinuous microemulsions form.
• To explore the influence of charge on polymer blend self-assembly.

Main Methods:

• Small-angle neutron and X-ray scattering (SANS/SAXS).
• Dynamic mechanical spectroscopy (DMS).
• Analysis of a ternary blend of poly[(oligo(ethylene glycol) methyl ether methacrylate-co-oligo(ethylene glycol) propyl sodium sulfonate methacrylate)]-b-polystyrene (POEGMA23-PS) diblock copolymer and its constituent homopolymers.

Main Results:

• Morphological transitions observed: layered superlattice to swollen lamellae to bicontinuous microemulsion (BμE) to phase separation.
• The BμE phase occurs between 85-90% homopolymer addition, near the Lifshitz point.
• A BμE with 26 nm periodicity was achieved in a charged system, which is unexpected.

Conclusions:

• A bicontinuous microemulsion can be formed in a partially charged polymer blend, contrary to expectations.
• The presence of charge does not preclude the formation of complex, disordered structures.
• This work expands the understanding of self-assembly in charged polymer systems and their potential applications.