Lyotropic Morphology Transition of Double Zwitterionic Diblock Copolymer Aqueous Solutions

Polymer concentration-dependent aqueous lyotropic morphology transition of a double zwitterionic diblock copolymer composed of a poly(carboxybetaine methacrylate) (PCB) and poly(sulfobetaine methacrylate) (PSB) is unraveled employing small-angle X-ray scattering. Salt-free aqueous solutions of the well-defined diblock copolymer produce ordered periodic structure and the morphology transforms from hexagonally close-packed cylinder to lamellar with decreasing the polymer concentration. The morphology transition is induced by the preferential distribution of water molecules into the PCB domains below threshold polymer concentration because of the limited water capacity of the PSB network domains. The volume fraction modulation causes the instability of phase boundary curvature urging the morphology transition. The precise ordered nanostructure control of the highly biocompatible double zwitterionic block copolymers is valid for responsive biocompatible molecular design in biomaterials.

Automated summary

This study reveals that the aqueous morphology of a double zwitterionic diblock copolymer undergoes transition dependent on polymer concentration, changing from a hexagonally close-packed cylinder structure to a lamellar structure. The preferential distribution of water molecules into specific domains below a certain polymer concentration threshold induces this morphology transition.