Fragmentation Kinetics in Block Copolymer Micelles: Dominant Effect of Core Block Length on Molecular Weight Dependence

초록

The block copolymer's molecular weight (MW) is considered one of the crucial factors influencing its micelle fragmentation kinetics. While several reports have explored the MW dependence theoretically and experimentally, there are still debates on how block length affects fragmentation rate and what block length governs the kinetics. In this work, we studied the MW effect of core and corona block on micelle fragmentation kinetics using two series of 1,2-polybutadiene-b-poly(ethylene oxide) (PB-b-PEO) with fixed NPB, core (degree of polymerization of the core block) and various NPEO, corona. We found that the relaxation time (τ) through micelle fragmentation exhibits a power-law correlation as τ~ Ncore1.2XNcorona0.6. The stronger Ncore dependence indicates higher core free energy from core extension in transition state.