Interactions between fluorocarbon surfaces in aqueous nonionic block copolymer solutions

• The interaction between solid fluorocarbon surfaces immersed in aqueous solutions of a poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) block copolymer (Proxanol 268) has been determined after different adsorption times. It was found that the compressed layer thickness is independent of the adsorption time, whereas the range of the repulsive force decreases during the first hours. This is interpreted as evidence for a decreasing fraction of polymer tails in the adsorbed polymer layer. A weak attractive force is observed when Proxanol coated surfaces are separated from contact. The presence of this attraction on separation only indicates structural changes in the block copolymer layer when two such layers on opposing surfaces are in contact for a prolonged time. Most of the Proxanol layer is easily desorbed by dilution with water. These results are discussed in connection with the known properties of perfluorocarbon emulsions coated with the same block copolymer.

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