Vesicle formation

In this chapter, the spontaneous vesicle formation of amphiphilic molecules in an aqueous solution is studied employing dissipative particle dynamics simulation. The amphiphilic molecule is represented by a coarse-grained model, which contains a hydrophilic head group and a hydrophobic tail group. Water is modeled by particles in the same way, with one particle representing a group of several H₂O molecules. In the dissipative particle dynamics simulation, starting with either a randomly dispersed system or a bilayer structure of the amphiphile for the initial condition, spontaneous vesicle formation via an intermediate state of an oblate micelle or a bilayer membrane is observed. The membrane fluctuates and encapsulates water particles and then closes to form a vesicle. During the process of vesicle formation, the energy of the hydrophobic interaction between the amphiphile and water reduces. Furthermore, it is found that the aggregation process is faster for two-tailed amphiphiles than for single-tailed amphiphiles.