DETERMINATION OF THE NU-EXPONENT FOR SOLUBLE POLYMERIC MONOLAYERS AT AN AIR-WATER-INTERFACE

The scaling theory predicts that the surface pressure Pi of polymer mo nolayers in the semidilute region varies with the surface concentratio n Gamma according to the power law Pi similar to Gamma(y), where y=2v/ (2v-1). For spread polymeric films, it has been established that exper iments were indeed in good agreement with the theory. We proposed a te st of the scaling theory for adsorbed polymeric monolayers by measurin g the high-frequency limit of the surface modulus epsilon 0 as a funct ion of the surface pressure Pi (it is shown that epsilon 0=y Pi). The exponent v for soluble polymer samples of poly(ethylene oxide), Pluron ic F127, Pluronic F68, and poly(vinyl alcohol) are found to be ca. 0.7 7, in agreement with the scaling theory for the good solvent condition . The experimental value for methylcellulose is v=0.64, which suggests that the air/water interface behaves as a poor solvent for the polyme r.