SPREAD AND ADSORBED MONOLAYERS OF HYDROXYPROPYL CELLULOSE AND HYDROXYETHYL CELLULOSE AT THE AIR-WATER-INTERFACE

Spread and adsorbed monolayers at the air-water interface of various molecular weight grades of hydroxypropyl cellulose (HPC) and hydroxyethyl cellulose (HEC) have been compared using a surface light scattering technique and have been shown to exhibit almost identical surface viscoelastic properties. Data from spread monolayer surface pressure isotherms have been used to analyze initial adsorption kinetics in the context of a simple diffusion model, and diffusion constants estimated are in very good agreement with independently determined values. Adsorption of HPC and HEC, which occurs independent of molecular weight over a wide concentration range, appears to produce a monolayer with about 64% and 49%, respectively, of the monomer units "adsorbed" at the interface and the rest "desorbed" into the aqueous subphase. This is consistent with the relative degree of hydrophobicity of these polymers. © 1990.