The self-assembly of the comb-coil poly(styrene-isoprene) block copolymers (S-graft-I)-block-S in polyisoprene (PI) selective solvents was investigated using dynamic light scattering (DLS) and atomic force microscopy (AFM). The copolymers of this architecture can only micellize into spherical morphology in heptanes. And these spherical micelles exhibit an unexpected bimodal size distribution. Besides the traditional polystyrene(PS)-PI phase separation mechanism, a comb-coil phase separation mechanism is proposed. And the formation of these bimodal micelles is suggested originating from the coexistence of these two mechanisms. Furthermore, the effects of selectivity, branch number and branch length on the self-assembly behaviors were studied using DLS and transmission electron microscope (TEM).

Key words: comb-coil copolymer, self-assembly, bimodal distribution, selectivity, branch number, branch length