DETERMINATION OF INTERFACIAL-TENSIONS FOR LATEX-PARTICLES

The possibility of measuring in situ the interfacial tension at the mo nomer-swollen polymer-water interface of synthetic latices is consider ed in detail. Experimental measurements of certain liquid or vapor pha se properties of the latex can, in principle, yield values of the desi red interfacial tension. This technique requires the evaluation and co mparison of the Flory-Huggins term and the Morton term of the thermody namic expression for the chemical potential of the monomer in the late x particle. While each term can be evaluated, it turns out that the re lative magnitudes of the two terms are such that unrealistically high precision is required in the experimental measurements for this techni que to be useful for obtaining reasonably accurate interfacial tension s. At saturated swelling conditions with highly surface-active emulsif iers (e.g., sodium dodecyl sulfate), the interfacial tension values ob tained have a precision of only about +/-50%. The realibility of these approximate values degrades rapidly as one moves away from saturation conditions, so as to render in situ experimental techniques inappropr iate for gaining accurate knowledge about the surface energy at the la tex particle-water interface at any monomer-polymer ratio. (C) 1994 Jo hn Wiley & Sons, Inc.