Synthesis and Self-Assembly of Brush-Type Poly[poly(ethylene glycol)methyl ether methacrylate]-block-poly(pentafluorostyrene) Amphiphilic Diblock Copolymers in Aqueous Solution

Well-defined fluorinated brush-like amphiphilic diblock copolymers of poly[poly(ethylene glycol)methyl ether methacrylate] (P(PEGMA)) and poly(pentafluorostyrene) (PPFS) have been successfully synthesized via atom transfer radical polymerization (ATRP). The self-assembly behavior of these polymers in aqueous solutions was Studied using H-1 NMR, fluorescence spectrometry, static and dynamic light scattering and transmission electron microscopy techniques. The micellar structure comprised of PPFS as the core and brush-like (hydrophobic main chain and hydrophilic branches) polymers as the coronas. The hydrodynamic radius (R-h) of the micelles in aqueous solution was in the nanometer range, independent of the polymer concentration, consistent with a closed association model. Diblock copolymers with a longer P(PEGMA) block formed micelles with smaller R-h and lower aggregation numbers consistent with an improved solubilization of the core. The micelles possessed a thick hydration layer its verified by the ratio of the radius of gyration, R-g to the hydrodynamic radius, R-h. The aggregation number and ratio of R-g to R-h, were observed to increase with temperature (20-50 degrees C), while the R-h of the micelle decreased slightly over the same temperature range. An increase in temperature induced the brush-like PEG segments in the corona to dehydrate and shrink while forming micelles with larger aggregation numbers.