Surface Force Measurement. Interactions between Interfaces Coated with Block Copolymers.

Abstract

In this paper we describe some measurements of the interactions between interfaces coated with block copolymers of ethylene oxide (E) and butylene oxide (B). We used two types of surface force techniques for determining the forces between hydrophobic surfaces across aqueous solutions of the diblock copolymer B8E41. With the help of the interferometric surface force technique the adsorbed layer thickness could be determined as well as the range and distance dependence of the steric force. The results obtained with a non-interferometric surface force technique agreed very well with the ones obtained using the interferometric technique provided that one takes into account the compressibility of the adsorbed polymer layer. The steric interactions between two air-water inferfaces with adsorbed B8E41, are less long-ranged than the interaction between hydrophobic solid surfaces coated with the same polymer. This result is not yet understood. The range of the steric force in foam lamella stabilized by the diblock copolymer is found to be much more long ranged than that of the triblock copolymer E20B8E20. The reason for this is that the triblock copolymer adsorbs less and forms smaller tails.