Diffusion in Lamellae, Cylinders, and Double Gyroid Block Copolymer Nanostructures

Area of Science:

• Materials Science
• Polymer Science
• Chemical Engineering

Background:

• Block copolymers self-assemble into diverse nanoscale morphologies.
• Understanding transport phenomena in these structures is crucial for applications like membranes and drug delivery.
• Previous models provided limited insights into diffusion within complex co-continuous structures.

Purpose of the Study:

• To quantify and compare penetrant transport rates through various block copolymer morphologies.
• To investigate the influence of morphology type and volume fraction on diffusion coefficients.
• To identify optimal morphologies for efficient molecular transport.

Main Methods:

• Confined random walk simulations were employed to model penetrant diffusion.
• Coarse-grained simulations were utilized to represent block copolymer structures.
• Diffusion was analyzed in lamellar, cylinder, and double gyroid morphologies.

Main Results:

• Diffusion in randomly oriented cylinder and lamellar morphologies was found to be 1/3 and 2/3, respectively, compared to homopolymers.
• Diffusion in the double gyroid structure varied with volume fraction: 0.47-0.55 (minority phase, 30-50 vol%) and 0.73-0.80 (majority phase, 50-70 vol%).
• Lamellar morphology demonstrated superior transport properties among standard minority phase structures.

Conclusions:

• Lamellar block copolymer morphology is preferable for efficient molecular transport.
• The double gyroid structure's transport properties are highly dependent on the volume fraction of its phases.
• These findings guide the design of block copolymer materials for targeted transport applications.