Synthesis and Solution Self-Assembly Properties of Cyclic Rod-Coil Diblock Copolymers.

Typical cyclic diblock polymers are synthesized from their linear precursors via the ring-closure strategy in dilute conditions. Here we demonstrate a pseudo-high-dilution condition strategy for the efficient synthesis of cyclic rod-coil diblock copolymer from its linear precursor in selective solvents. The critical association concentration (CAC) of linear precursor is used for the control of unimer concentration during cyclization, while high copolymer synthetic concentrations are achieved via the dynamic equilibrium between unimers and micelles. The effects of CAC and micelle concentration on cyclization yield are studied and pure cyclic rod-coil diblock copolymer was obtained after azide resin treatment. Property investigations show the cyclic rod-coil copolymer has a larger second virial coefficient than its linear counterpart and self-assembles in selective solvents to form larger but looser spherical micelles due to its constraint topological structure.