Phase Separation Pathways of Chiral Macromolecules at Liquid-Liquid Interfaces

The phase behavior of chiral macromolecules is one of the key subjects in chemistry, biology, and materials science. Here we take poly(L-lactic acid) (PLLA) and mesomeric poly(D, L-lactic acid) (mPLA) mixtures as a model system and investigate the phase separation behaviors in double emulsion droplets. At high mPLA compositions, phase separation creates transient bicontinuous networks or discrete domains at the liquid-liquid interface and eventually generates eyeball-like microcapsules. At low mPLA compositions, phase separation occurs first but is trapped by the lateral crystallization of PLLA, leading to spindle-like microcapsules. The dynamic pathways of phase separation can be further modulated by PLA-based amphiphilic block copolymers, so that microcapsules are configurable between the eyeball-, spindle-, and Janus-like structures. By comparing with phase separation on a plane substrate, we unveil that the phase separation dynamics at the double emulsion interfaces are significantly affected by interfacial properties and hydrodynamic effects. This work clarifies the phase transition dynamics of PLLA/mPLA mixtures at liquid-liquid interfaces and sheds insight into the phase behaviors of chiral macromolecules for their structural modulation.