Divergent self-assembly dynamics of squalene-derived bolaamphiphiles enabled by ethylene glycol-length-switchable...

Bolaamphiphiles were synthesized by introducing ethylene glycol groups at both terminal double bonds of squalene for the first time. The monolayer vesicle structures formed in aqueous media were elucidated by liquid cell and cryogenic transmission electron microscopy. The morphology of the self-assembled aggregates was found to be strongly dependent on the length of the ethylene glycol group. Notably, bolaamphiphiles bearing two tetra-ethylene glycol groups formed exceptionally ultra-small monolayer vesicles with an average diameter of 10 nm, which exhibited remarkable stability for a period of 180 days. Substitution with tri-ethylene glycol groups preserves the monolayer vesicular architecture while promoting a gradual size increase from 160 nm to 1600 nm over 180 days. The growth of particle diameter was elucidated to proceed via an Ostwald ripening-driven mechanism under diffusion-limited conditions. During the vesicle growth process, a biphasic pathway featuring two distinct diffusion coefficients was identified within the framework of the Lifshitz-Slyozov-Wagner theory, and we propose, to our knowledge, a mechanistic model in which each phase is governed by different driving forces.