We examine the kinetics of chain exchange of block copolymers between BCC-ordered spherical micelles, focusing on the influence of chain architecture on the kinetics. We compare linear AB, ABA and BAB block copolymers where the A block is the core-forming block. Our simulations are based on dynamical self-consistent field theory, which we have applied to block copolymer melts. We connect equilibrium micelle structure to dynamic effects by characterizing equilibrium properties such as micelle aggregation number, unimer fraction and equilibrium micelle size. The effects of the difference in equilibrium structure on chain exchange are found by measuring the chain exchange of labelled chains as well measuring chain self-diffusion for each chain architecture. We find that AB diblocks exchange and diffuse slower than both triblock architectures, while ABA triblocks exchange and diffuse much faster than the AB and BAB copolymers. To eliminate influences of equilibrium structure on dynamics and focus on architecture effects, we perform simulations of tracer triblocks in a constant array of BCC-ordered spherical micelles formed by AB diblocks. Comparisons between tracer diffusion coefficients show that BAB triblocks diffuse faster possibly due to the looping of the core block at the micelle core-corona interface than AB diblocks while ABA triblocks diffuse slower than AB diblocks because of the additional core block and the possibility of core blocks bridging between micelle cores.
- Dr. Paul Garrett, Chair
- Dr. Robert Wickham, Advisor
- Dr. An-Chang Shi (McMaster University)
- Dr. Stefan Kycia