Vesicles from the self-assembly of coil–rod–coil triblock copolymers in selective solvents

Self-assembled vesicles formed by symmetrical coil–rod–coil triblock copolymer in selective solvents are investigated by dissipative particle dynamics method. With varying the coil length Lc and the rod length Lr, five kinds of typically ordered micelles are observed, including the special vesicles formed in the range of the rod block ratio fr ≈ 30% ∼ 50% and the rod length Lr ≤ 9. The kinetic process of vesicle formation is also observed. The aggregates firstly experience the fusion, elongation, and deformation, and then encompass the solvents, and finally close up to a vesicle membrane, where the bilayer disc is observed as an intermediate phase transited from solid micelles to hollow vesicles. A scaling behavior of the average aggregate size with time is also obtained during the process of the self-assembly. Furthermore, the effects of polymer concentration fp and solvent property are discussed. Vesicle structure only appears in the range of fp = 6% ∼ 25%, where vesicle size exhibits a well linear increase with polymer concentration. Meanwhile, vesicle size decreases with an increase in the interactions aCS between coil blocks and solvents. Due to the interfacial energy increased with aCS, the system minimizes interfacial energy by compressing the vesicle size.