Morphology and nanostructure of amphiphilic polymer micelles with fluorinated core and nonfluorinated corona

Copolymers with blocks of different affinities for solvents behave as amphi philic molecules. Amphiphilic block copolymers are surface-active and form polymer micelles in solutions. The structure of polymer micelles is charact erized in the existence of domains where the affinities for solvents differ . When one of the blocks has a fluorinated pendant side chain with both fun ctionalities of hydrophobicity and oleophobicity, the block copolymers are expected to function as a novel ''multidomain" or ''multicompartment" organ ism. The micelle formation abilities of poly (methyl methacrylate)-block-po ly (2-perfluorooctylethyl methacrylate) (PMMA-block-PFMA), poly(tert-butyl methacrylate -block-poly (2-perfluorooctylethyl methacrylate) (PtBMA-block- PFMA), and poly (methacrylic acid)-block-poly (2-perfluorooctylethyl methac rylate) (PMAA-block-PFMA) were examined. Polymer micelles of PMMA-block-PFM A and PtBMA-block-PFMA in organic solvents are spherical and consist of two -layers : an oleophobic core of 15 nm radius and an oleophilic corona of 15 nm thickness. The elongated micelles were constructed by PMAA-block-PFMA i n an aqueous solution as well as in an ethanol solution. The micelles in th e aqueous solution extend more with addition of salt due to the electric sh ielding effect. When pH of the solution is changed. nonionic PMAA-block-PFM A micelles at acid pH grow into ionic larger micelles at alkaline pH. It is assumed that the PMAA block extends owing to the electrostatic repulsion o f ionic side chains, resulting in the closed packing of copolymers in micel les. The adsorption behavior of PMAA-block-PFMA micelles at the interface d epends on the affinity of the interface.