January 29, 2010
View Full PaperMechanism of Molecular Exchange in Diblock Copolymer Micelles: Hypersensitivity to Core Chain Length
Key Points
- This research aims to explore how the core chain length of diblock copolymers affects molecular exchange in micelles.
- Time-resolved small-angle neutron scattering measurements were conducted.
- Micelles were formed from isotopically labeled diblock copolymers with varying core block lengths.
- Temperature variations were analyzed to assess the effect on exchange rates.
- Molecular exchange rate R(t) is influenced by the thermal dynamics of the core polymer.
- Changes in core block length N cause significant alterations in R(t) due to thermodynamic penalties.
- R(t) exhibits an approximately logarithmic relationship with respect to varying N.
Abstract
Molecular exchange between spherical micelles formed from isotopically labeled diblock copolymers was investigated using time-resolved small-angle neutron scattering measurements. Temperature changes affect the micelle exchange rate R(t) consistent with melt dynamics for the core polymer. Varying the core block length N produces gigantic changes in R(t) due to the thermodynamic penalty associated with ejecting a core block into the surrounding solvent. This hypersensitivity, combined with modest polydispersity in N, leads to an approximately logarithmic R(t).