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Nanoparticles of polyampholyte-surfactant complexes with perfluorododecanoic acid

: Thünemann, A.F.; Wendler, U.; Jaeger, W.; Schnablegger, H.


Langmuir. The ACS journal of surfaces and colloids 18 (2002), Nr.11, S.4500-4504
ISSN: 0743-7463
ISSN: 1520-5827
Fraunhofer IAP ()

Polyampholytes were synthesized and complexed with perfluorododecanoic acid. This produces highly fluorinated water-soluble nanoparticles, which are long-term stable. The polyampholytes are copolymers of styrylmethyl(trimethyl)ammonium chloride, methacrylic acid, and methyl methacrylate having more cationic monomers (28-100 mol %) than anionic monomers (0-16%). The cationic monomers form a complex with perfluorododecanoate ions to create neutral entities that aggregate while the negatively charged methacrylic monomers prevent a macroscopic precipitation such as normally observed in fluorinated complexes. Negatively charged nanoparticles, which have zeta potentials of about -40 mV, are formed as a result of the combined complexation and stabilization. Small-angle X-ray scattering investigations reveal that the particles are anisotropic. For example, disk-shaped particles with a diameter of D greater than or equal to 30 nm and a height of 2.2 nm were formed for a high number of complexing groups (79 mol %). Cylindrical-shaped particles with lengths of H greater than or equal to 25 nm and radii of 1.5 nm were produced for a medium number of complexing groups (57 mol %). Fluorescence spectroscopy with pyrene as the probe was used to determine the critical aggregation concentrations of the particles which are in the range 0.01-0.06 g L-1.