Tuning the pore composition by two simultaneous interfacial self-assembly processes: breath figures and coffee stain

Area of Science:

• Materials Science
• Polymer Chemistry
• Surface Science

Background:

• Microstructured porous films are crucial for various applications.
• Controlling additive distribution in porous materials is challenging.
• The breath figures method offers a route to create complex film architectures.

Purpose of the Study:

• To investigate the influence of amphiphilic additive structure on their distribution within microstructured porous films.
• To understand the role of polymer-solvent interactions and surface tension in the breath figures process.
• To characterize the resulting film morphology and additive localization.

Main Methods:

• Preparation of microstructured porous films using the breath figures approach.
• Utilizing polymer blends of polystyrene with synthetic block copolymers or commercial surfactants.
• Solvent: Tetrahydrofuran.
• Characterization via Confocal micro-Raman spectroscopy.

Main Results:

• Amphiphilic additives preferentially locate within the cavities of the porous films.
• The distribution of block copolymers within cavities depends on their solubility and surface properties.
• Homogeneous distribution observed for copolymers insoluble in water; ring-like deposition (coffee-stain effect) for water-soluble copolymers.
• Surfactants modified the coffee-stain effect, leading to pore-bottom coverage by the copolymer.

Conclusions:

• The breath figures mechanism effectively directs amphiphilic additives into film cavities.
• Additive structure dictates its localization pattern (homogeneous, ring-like, or pore-bottom) within the cavities.
• Surface properties of additives significantly influence their distribution and the resulting film morphology.