Wetting transitions within membrane compartments.

A biomimetic membrane in contact with several aqueous phases is theoretically studied using a combination of Helfrich curvature elasticity theory for fluid membranes and self-consistent field theory for polymers in solutions. Two phases that are thermodynamically formed by phase separation of aqueous solutions, as well as stable and metastable shapes of fluid vesicles, have been observed. The wetting transitions from complete to partial wetting and to complete dewetting are identified within a membrane compartment. The dependences of wetting transitions on material parameters, such as the intrinsic contact angles θin, the interaction strengths between the polymers χαβ and between the membrane and the polymer ηp, and impermeability of the membrane to the enclosed polymers ζp, are investigated. For a given χαβ, impermeability ζp and affinity to the membrane ηp, θin is found to be a constant and independent of the reduced volume of vesicles and the volume fraction of two phases.