Effect of Selective Perfluoroalkylation on the Segregation Strength of Polystyrene−1,2-Polybutadiene Block Copolymers

A series of partially fluorinated (C6F13H-modified) polystyrene-b-1,2-polybutadiene (PS-b-1,2-PB) copolymers were prepared by the reaction of a model PS-b-1,2-PB copolymer with n-C6F13I followed by substitution of hydrogen for the iodine by hydrogenolysis. The morphologies and domain spacings of the ordered samples at 120 and 195 °C were determined as a function of C6F13H modification extent using small-angle X-ray scattering (SAXS). From the domain spacings an effective interaction parameter (χeff) between the PS and partially C6F13H-modified 1,2-PB blocks was estimated. The χeff at 120 °C increases significantly with fluorination, from ca. 0.05 (0 mol % C6F13H modification) to ca. 0.75 (80 mol % C6F13H modification). The order−disorder transition temperature (TODT) for a partially C6F13H-modified PS-b-1,2-PB (25 mol %) was determined to be 186 ± 3 °C, using rheology and static birefringence. From self-consistent mean-field theory χeff for this block copolymer is estimated to be 0.16 at TODT, which agree...