High-χ, low-N micelles from partially perfluorinated block polymers

Abstract

Kinetically trapped (“persistent”) micelles enable emerging applications requiring a constant core diameter. Preserving a χN barrier to chain exchange with low-N requires a commensurately higher χ_{core–solvent} for micelle persistence. Low-N, high-χ micelles containing fluorophobic interactions were studied using poly(ethylene oxide-b-perfluorooctyl acrylate)s (O₄₅F_X, x = 8, 11) in methanolic solutions. DLS analysis of micelles revealed chain exchange only for O₄₅F₈ while SAXS analysis suggested elongated core block conformations commensurate with the contour lengths. Micelle chain exchange from solution perturbations were examined by characterizing their behavior as templates for inorganic materials via SAXS and SEM. In contrast to the F₈ analog, the larger χN barrier for the O₄₅F₁₁ enabled persistent micelle behavior in both thin films and bulk samples despite the low T_g micelle core. Careful measures of micelle core diameters and pore sizes revealed that the nanoparticle distribution extended through the corona and 0.52 ± 0.15 nm into the core–corona interface, highlighting thermodynamics favoring both locations simultaneously.