New Morphologies and Phase Transitions of Rod–Coil Dendritic–Linear Block Copolymers Depending on Dendron Generation and Preparation Procedure

Amphiphilic rod–coil dendritic–linear block copolymers PEG­(G_<i>m</i>)-<i>b</i>-PMPCS (where <i>m</i> is the number of dendron generation, and <i>m</i> = 1, 2, 3) composed of a semirigid Percec-type dendron with hydrophilic poly­(ethylene glycol) (PEG) tails and a rod-like mesogen-jacketed liquid crystalline polymer, poly­{2,5-bis­[(4′-methoxy-phenyl)­oxycarbonyl]­styrene} (PMPCS), were successfully prepared. The self-assembled structures undergo a transition from vesicles through large compound vesicles (LCVs) to short cylindrical micelles with increasing dendron generation. PEG­(G₂)-<i>b</i>-PMPCS forms stable LCVs with porous surfaces of a narrow size distribution in a mixed solvent of tetrahydrofuran and water. The formation mechanism of the supramolecular structure with nano- and microsized scales is studied through changing the rate of water addition. It is composed of two steps: morphological transformation and vesicles fusion or differentiation. Vesicles are precursors for LCVs regardless of what the initial morphology is. However, the final LCV structures are different. Slow addition of water produces spherical LCVs, while those formed during fast water addition are irregular (like deformed spherical) LCVs