ELLIPSOMETRIC STUDY OF POLYMER MONOLAYERS SPREAD AT THE AIR-WATER INTERFACE. 2. ADSORBED AMOUNT OF POLYMERS.

Ellipsometry has been used to calculate the refractive index and thickness of polymer monolayers of poly(ethylene oxide) (PEO), poly(tetrahydrofuran) (PTHF), poly(vinyl acetate) (PVAc), and poly(methyl methacrylate) (PMMA) spread at the air-water interface as a function of surface concentration and surface pressure. From the refractive index and thickness of the adsorbed monolayers we attempted to calculate the adsorbed amounts of polymers in the monolayers in terms of the Lorentz-Lorenz relation for an ideal mixed layer of polymer and surrounding media as a function of the refractive index n//s of the surrounding media. The adsorbed amount of polymer so calculated for n//s equals 1 corresponding to air is much larger than that for n//s equals 1. 334 corresponding to water. The latter adsorbed amount is in agreement with the real spread amount of polymer in the entire surface concentration range irrespective of polymer species. This agreement indicates that the polymer chains are surrounded by water molecules by taking an extended conformation normal to the water surface for PTHF and PVAc and a flattened one for PEO and PMMA at higher surface concentration.