Morphologically Tunable Coassembly of Double Hydrophilic Block Polyelectrolyte with Oppositely Charged Fluorosurfactant

We report on the formation and structure development of polyelectrolytesurfactant complexes, PES, of double hydrophilic block copolymers poly(sodium 2-sulfamate-3-carboxylate isoprene)-block-poly(ethylene oxide), PSCIPEO, and cationic fluorosurfactant, N-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)pyridinium chloride, HFDPCl. We compare the behavior of four PSCIPEO samples differing in comonomer composition and polyisoprene block modification degree. Coassembled coreshell nanoparticles with the core formed by the PSCI/HFDPCl complex and the shell of PEO blocks were characterized by microscopic techniques (cryogenic transmission electron microscopy, atomic force microscopy) and by small-angle neutron scattering. Interactions between PSCIPEO and HFDPCl were studied by isothermal titration calorimetry. We show that the bulky fluorosurfactant ions drive the coassembly toward structures with less curved interfaces such as cylindrical and wormlike micelles or vesicles. We also demonstrate the role of hydrophobic interactions in the system induced by the presence of unmodified polyisoprene units which in the case of the PSCIPEO copolymer with a low degree of modification lead to formation of PSCIPEO micelles and prevent the copolymer from the coassembly with HFDPCl.