Comparison of the monolayer formation of fluorinated and nonfluorinated amphiphilic block copolymers at the air-water interface

Series of fluorinated amphiphilic diblock copolymers poly(ethylene oxide)-b-poly(heptafluorobutyl methacrylate) (PEO-b-PHFBMA) and nonfluorinated analogue copolymers poly(ethylene oxide)-b-poly(n-butyl methacrylate) (PEO-b-PBMA) with different lengths of hydrophobic blocks were synthesized. Their interface properties at the air-water interface were investigated using surface pressure and X-ray reflectivity (XR) measurements on the Langmuir trough. The fluorinated species have shown a distinct transition from flatlying to standing side chains, whereas the nonfluorinated ones have no indication for a significant amount of flat-lying side chains. The water surface is covered by a single layer, which is proved by XR measurements of PEO-b-PHFBMA. The obtained thickness and electron density can be related to the hydrophobic part of the copolymer by a simple consistency check: The total numbers of electrons from the fit of the XR curve should agree with the numbers of electrons in the corresponding block.

DDC Class

530: Physik

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Z.L. gratefully acknowledges AIP Piesteritz eV for financial support.

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Comparison of the monolayer formation of fluorinated and nonfluorinated amphiphilic block copolymers at the air-water interface