Block copolymer micelles are often prepared or used in a non-equilibrium state, but remarkably little is understood about the mechanisms by which these micelles relax toward equilibrium. We examine the fragmentation kinetics of spherical micelles formed by a 1,2-polybutadiene-<i>block</i>-poly(ethylene oxide) copolymers in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide-based ionic liquids. In this system, the core-forming block is 1,2-polybutadiene (and the corona-forming block is poly(ethylene oxide). Using a direct dissolution technique, initial micelles are prepared that are significantly larger than equilibrium. A combination of techniques is used to follow the subsequent decrease in size, including dynamic light scattering, small-angle X-ray scattering, and especially liquid-phase transmission electron microscopy. Experimental variables include the interfacial tension between the core and the solvent (modulated through the solvent cation structure), annealing temperature, and copolymer concentration and molecular weight. Consistent results are obtained among the various experiments, but in several respects the results are quite surprising, as will be discussed.

Watching micelles break into two

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.