Gentle evaporation of dichloromethane from monodispersed droplets composed of a mixture of poly(vinyl acetate) and polystyrene dissolved in dichloromethane caused thermodynamic instability and phase separation into hydrophobic polystyrene and hydrophilic poly(vinyl acetate) halves. Poly(vinyl acetate) regions are more porous due to higher instability of this polymer in dichloromethane.
Janus microparticles formed by spinodal instability within microfluidically-generated droplets —

Gentle evaporation of dichloromethane from monodispersed droplets composed of a mixture of poly(vinyl acetate) and polystyrene dissolved in dichloromethane caused thermodynamic instability and phase separation into hydrophobic polystyrene and hydrophilic poly(vinyl acetate) halves. Poly(vinyl acetate) regions are more porous due to higher instability of this polymer in dichloromethane.

https://fluids.ac.uk/files/01.2_Bifacial_particles_Low_magnification.1543870941.jpg