Diffusion of Selective Penetrants in Interfacially Modified Block Copolymers from Molecular Dynamics Simulations

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Microphase separated polymer systems exhibit complex structures and dynamics.
• Interfacial properties critically influence material behavior.
• Block copolymers offer tunable architectures for controlling phase separation.

Purpose of the Study:

• To investigate the influence of interfacial modification on the structure and dynamics of microphase separated polymer systems.
• To understand the role of small molecule penetrants in interfacially modified AB block copolymers.
• To elucidate the relationship between polymer architecture, interfacial properties, and diffusion.

Main Methods:

• Simple coarse-grained molecular dynamics simulations were employed.
• Symmetric AB block copolymers with random or tapered midblocks were studied.
• Diffusion of polymers and penetrants parallel to lamellar structures was analyzed.

Main Results:

• Normal tapering in block copolymers increased both polymer and penetrant diffusion rates with increasing taper length.
• Inverse tapered polymers showed nonmonotonic diffusion trends due to varying conformational states.
• Local monomer mixing was identified as the primary determinant of penetrant diffusion, overriding polymer conformation effects.

Conclusions:

• Interfacial modifications, particularly through tapering, significantly alter polymer system dynamics.
• The degree of local monomer mixing is the most critical factor governing penetrant diffusion.
• Understanding these structure-dynamics relationships is crucial for designing advanced polymer materials.