NONEQUILIBRIUM SIZE DISTRIBUTIONS OF FLUID MEMBRANE-VESICLES

We investigate nonequilibrium behavior of polydisperse ensembles of fl uid membrane vesicles by means of a diffusive Boltzmann transport equa tion that incorporates vesicle diffusion and reactions between vesicle s. This approach is used to study time evolutions of size distribution s of initially monodisperse vesicle ensembles. We investigate various nonequilibrium paths that ensembles of vesicles may follow during the equilibration process. Depending on the initial size distribution of v esicles, the thermodynamic equilibrium may be reached either via a fus ional growth of vesicles, or via their fissional decay. In the former case, typical vesicle size grows as R(t)similar to t(1/2) Until it sat urates to its equilibrium value, whereas in the latter case we find th at vesicle size decays in a finite time proportional to [R(0)](1/3), w here R(0) is the initial vesicle size. The latter behavior is related to the length scale dependence of membrane bending and saddle splay ri gidity.