SPECTROSCOPIC CHARACTERIZATION OF POLYMER ADSORPTION AT THE AIR SOLUTION INTERFACE

Infrared reflectance spectroscopy is used to investigate surface struc ture at the air-water interface for monomolecular layers of a semifluo rinated alcohol, CF3(CF2)(9)(CH2)(2)OH, and for water-soluble polymers of poly(ethylene oxide) samples end-capped with fluorinated hydrocarb on chains. In all cases, the fluorinated chain is highly ordered and o riented with the chain axis normal to the air-water surface. The highl y ordered structure extends into the poly(ethylene oxide) backbone of the end-capped polymer chains. Reflectance intensities of the CF2 stre tching vibrations of the water-soluble polymers provide a direct measu re of the surface concentration as a function of the bulk concentratio n and show that the Langmuir adsorption isotherm is strictly obeyed in the concentration range studied. There is no evidence of multiple lay ering at the surface. The Langmuir adsorption constant K was found to be 1.5 x 10(7) cm(3)/mol for poly(ethylene oxide) end-capped with CO(C F2)(8)CF3.