(346d) Penetrant and Ion Dynamics in Model Microphase Separated Copolymers | AIChE

(346d) Penetrant and Ion Dynamics in Model Microphase Separated Copolymers


Seo, Y. - Presenter, The Ohio State University
Brown, J. R., The Ohio State University
Hall, L., The Ohio State University
Nanostructured AB block copolymers have been of great interest for transport applications such as lithium ion battery electrolytes and CO2 separation membranes. Various nanostructures (lamellae, cylinder, gyroid, sphere) form as functions of the fraction of A monomer, A-B interaction strength, and molecular weight, and one can choose the A monomer to allow transport of the target molecules while the B monomer provides mechanical robustness. Here, we study both diblock and tapered AB block copolymers (TBCs) where a â??taperedâ? mid-block is inserted between two pure blocks of A and B monomers. The taper has a gradient in composition from pure A to pure B (or from pure B to pure A for an inverse taper) and taper length can be used an additional tuning parameter to control the nanostructure. A recent experiment shows a certain length of taper can improve both polymer and ion dynamics for battery electrolyte systems [1]. To provide physical insight into such results and predict which systems may improve transport, we perform molecular dynamics simulations using a simple coarse-grained bead-spring model. Monomer-sized penetrants with favorable interactions with one type of monomer are added to lamellar structures of normal and inverse TBCs at a range of taper length from 0% (diblocks) to 100% (gradient copolymer). We observe both polymersâ?? and penetrantsâ?? dynamics increase as taper length increases for normal TBCs but non-monotonically change for inverse TBCs. For the inverse TBCs, nonintuitive trends in the dynamics arise from competing effects of local A-B mixing and chain conformations. We have also considered salt-doped systems (with full long-ranged Coulomb interactions) to explore how ion transport is different than that of uncharged small penetrant molecules.

[1] W.-F. Kuan, R. Remy, M. E. Mackay, and T. H. Epps, III, RSC Adv. 5, 12597 (2015).