COMPATIBILITY OF POLYMER-CHAINS AT THE AIR-WATER-INTERFACE

Surface pressure measurements of binary mixtures among poly (ethylene oxide) (PEO), poly (methyl acrylate) (PMA), poly(vinyl acetate) (PVAc), and poly(methyl methacrylate) (PMMA) have been performed at the air/water interface using the Wilhelmy plate method as a function of mole fraction of one component in the binary mixture. From the plots of the experimental mean area of the mixed polymer films at a constant surface pressure as a function of the mole fraction of one component in the films, we estimated the compatibility or incompatibility of both polymers at the air/water interface. PEO/ PMMA mixtures and PMA/PVAc mixtures are compatible in their entire composition. In PVAc/ PMMA mixtures, the repulsive interaction is dominant, and the mixtures are thermodynamically unstable and should not be compatible. For PVAc/PEO mixtures, the attractive interaction is observed below the collapse surface pressure of PEO, i.e., 10 mN/m. Above this value, the surface pressures of the mixtures are almost independent of the composition. These results correlate well with the compatibility of the corresponding mixtures in the bulk state. © 1990, American Chemical Society. All rights reserved.