  We develop a multiscale simulation model for diffusion of solutes through
porous triblock copolymer membranes. The approach combines two techniques:
self-consistent field theory (SCFT) to predict the structure of the
self-assembled, solvated membrane and on-lattice kinetic Monte Carlo (kMC)
simulations to model diffusion of solutes. Solvation is simulated in SCFT by
constraining the glassy membrane matrix while relaxing the brush-like membrane
pore coating against the solvent. The kMC simulations capture the resulting
solute spatial distribution and concentration-dependent local diffusivity in
the polymer-coated pores; we parameterize the latter using particle-based
simulations. We apply our approach to simulate solute diffusion through
nonequilibrium morphologies of a model triblock copolymer, and we correlate
diffusivity with structural descriptors of the morphologies. We also compare
the model's predictions to alternative approaches based on simple lattice
random walks and find our multiscale model to be more robust and systematic to
parameterize. Our multiscale modeling approach is general and can be readily
extended in the future to other chemistries, morphologies, and models for the
local solute diffusivity and interactions with the membrane.
