Fragmentation Kinetics of Block Copolymer Micelles: Effect of Changing Interfacial Tension

Block copolymers offer great potential as drug delivery carriers, functional nanomaterials, and nanoreactors. The spherical micelles attain equilibrium predominantly by micelle fusion, fragmentation, and chain exchange mechanisms. The present study examines the fragmentation kinetics of 1,2-polybutadiene-b-poly(ethylene oxide) block copolymer micelles in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide-based ionic liquids to comprehend the role of the driving force for fragmentation, represented by the micelle size ratio Q/Q_eq. The micelle size ratio Q/Q_eq was varied by the strategic mixing of different ionic liquids with varying interfacial tensions. The interfacial tensions for a series of ionic liquids with 1-2-polybutadiene homopolymer were measured using a pendant drop test. Micelles were characterized using in-situ dynamic light scattering, small-angle X-ray scattering, and transmission electron microscopy. Dilution of a micellar solution with a less selective solvent is found to influence the fragmentation kinetics.