Path-dependent morphologies in oil/water/diblock copolymer mixtures.

Area of Science:

• Polymer Science
• Materials Chemistry
• Supramolecular Chemistry

Background:

• Amphiphilic block copolymers self-assemble into micelles and vesicles in binary systems, exhibiting low critical micelle concentrations (CMCs).
• Understanding the influence of ternary components on copolymer self-assembly is crucial for developing advanced materials.
• The non-ergodic nature of block copolymers can lead to complex, nonequilibrium phase behaviors.

Purpose of the Study:

• To investigate the self-assembly of a poly(1,2-butadiene-b-ethylene oxide) diblock copolymer in binary and ternary mixtures with water and 1,5-cyclooctadiene.
• To characterize the resulting morphologies and understand the effect of component mixing order.
• To explore potential new processing strategies for creating desirable self-assembled structures.

Main Methods:

• Preparation of binary (OB/W, OB/C) and ternary (OB/W/C, OB/C/W) mixtures using a poly(1,2-butadiene-b-ethylene oxide) diblock copolymer.
• Morphological characterization using small-angle X-ray scattering (SAXS).
• Microstructural analysis via cryogenic scanning electron microscopy (cryo-SEM).

Main Results:

• Mixing 1,5-cyclooctadiene with premicellized copolymer in water induced micelle core swelling and fusion, forming 3D network structures.
• Combining water with copolymer premixed in 1,5-cyclooctadiene resulted in phase separation with water-swollen poly(ethylene oxide) bilayers forming uniform vesicles.
• Both network and vesicle structures remained stable for at least one month.

Conclusions:

• The mixing sequence of amphiphilic block copolymers, water, and 1,5-cyclooctadiene significantly dictates the final microstructure.
• Non-equilibrium phase behavior, driven by the non-ergodic character of the copolymer, enables the formation of distinct, stable morphologies from a single formulation.
• This study demonstrates a versatile approach for tailoring self-assembled nanostructures for potential applications.