We use umbrella sampling to compute the free energy trajectory of a single chain undergoing expulsion from an isolated diblock copolymer micelle. This approach elucidates the experimentally unobservable transition state, identifies the spatial position of the maximum free energy, and reveals the chain conformation of a single chain as it undergoes expulsion. Combining umbrella sampling with dissipative particle dynamics simulations of A4B8 micelles reveals that the core block (A) of the expelled chain remains partially stretched at the transition state, in contrast with the collapsed state assumed in some previous models. The free energy barrier increases linearly with the Flory-Huggins interaction parameter χ up to large interaction energies, where the structure of the otherwise spherical core apparently deforms near the transition state.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation Polymers Program (DMR-1707578 and DMR-2103630) and by an NSF Graduate Research Fellowship (S.C.S.). The authors acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota for providing resources to perform the simulations in this work and Vaidyanathan Sethuraman for helpful discussions surrounding this work.
© 2021 American Chemical Society.
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't