AN ENSEMBLE OF VESICLES IN 2 DIMENSIONS

An off-lattice model of a vesicle assembly in two dimensions is studie d by use of computer simulation techniques. The vesicles are represent ed as closed, self-avoiding tethered chains with bending rigidity. We present studies for a system of fluctuating vesicle configurations, wh ere the total number of monomers is fixed, but the vesicle size distri bution may vary, i.e. the vesicles can fuse or break up. The phase dia gram obtained in the case of zero osmotic pressure contains a vesicle phase with broken in-out symmetry and a symmetric ''bicontinuous'' pha se. The phases are separated by a line of Ising-type second-order phas e transitions, and the functional form of the phase boundary is derive d from simple scaling arguments.