Solvent-Induced Swelling Behaviors of Microphase-Separated Polystyrene-block-Poly(ethylene oxide) Thin Films...

Area of Science:

• Polymer Science and Engineering
• Nanoscience and Nanotechnology
• Materials Chemistry

Background:

• Block copolymers self-assemble into well-defined nanostructures, vital for nanoscience and nanotechnology.
• Understanding solvent effects on polymer microdomain properties is critical for their effective utilization.

Purpose of the Study:

• To investigate the impact of ethanol and water vapor on the physicochemical properties of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) microdomains.
• To elucidate the mechanism of solvent-induced swelling and permeation within block copolymer nanostructures.

Main Methods:

• In situ spectroscopic ellipsometry to monitor film thickness changes.
• Single-molecule fluorescence spectroscopy (ensemble and tracking) to probe molecular dynamics and solvent interactions.
• Fourier-transform infrared (FTIR) spectroscopy to assess the amorphous nature of polymer domains.

Main Results:

• PS-b-PEO films exhibited a unique increase and subsequent decrease in thickness upon exposure to ethanol vapor, unlike homopolymer films.
• Evidence of PEO microdomain swelling was observed, supported by fluorescence emission redshifts and altered diffusion of probe molecules.
• FTIR data confirmed the amorphous structure of PEO domains, explaining their higher susceptibility to ethanol permeation.

Conclusions:

• The PEO microdomains within PS-b-PEO block copolymers are susceptible to swelling by ethanol vapor due to their amorphous nature.
• The observed thickness changes and molecular dynamics provide insights into solvent-polymer interactions crucial for nanostructure design.
• These findings are significant for developing controlled self-assembly processes and functional nanomaterials.