The aggregation behavior of cyclic rod-coil (RC) diblock copolymers in dilute solutions is investigated through dissipative particle dynamics simulation. By varying the rod length and coil length

cyclic RC copolymers in selective solvents exhibit various morphologies

including spherical micelle

vesicle

bilayer disc

and ribbon bundle structure. Compared with the equivalent linear RC copolymer

only spherical micelle and barrel bundle phase are observed. Rod length is the major factor that controls the liquid-crystalline behavior of RC copolymer systems

while the coil length has a secondary effect on the aggregate morphology. The size of rod bundle varies with the coil length

especially for the end-toend ribbon bundle and side-by-side barrel bundle

which are assembled by cyclic and linear RC copolymer solutions. This finding indicates that the ribbon bundle or nanofiber-like structure in cyclic RC copolymers can be obtained by controlling the rod length and coil length

and thus the optical and electrical properties of RC copolymer would be further controlled and optimized. Results illustrate that cyclization of a linear RC copolymer induces remarkable differences in the rod arrangement and aggregation behavior

thereby indicating the competition between interfacial energy

rod orientational entropy

coil stretching entropy

and packing constraints.