Krafft Points, Critical Micelle Concentrations, Surface Tension, and Solubilizing Power of Aqueous Solutions of Fluorinated Surfactants

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Krafft Points, Critical Micelle Concentrations, Surface Tension, and Solubilizing Power of Aqueous Solutions of Fluorinated Surfactants

Authors: Hironobu and Kozo Shinoba

Journal: The Journal of Physical Chemistry, Vol. 80, No. 22, 1976, p2468-2470


Introduction

This paper discusses the Krafft points, critical micelle concentrations (cmc), surface tension above the cmc, and solubilizing power in aqueous solutions of perfluoroalkane carboxylates as functions of fluorocarbon chain length.

The surface tension of these types of solutions is lower than that for ordinary surfactants. Fluorinated surfactants are very stable and have special industrial uses. The longer chain surfactants are more surface active and have high solubilization at low concentrations (compared to shorter chain surfactants). However, the Krafft point increases with increasing hydrophobic chain length. The Krafft point is the point above which ionic surfactants form micelles (and therefore dissolve well). Before this paper was published, it was shown that the kinds of [gegenions][1] affect the Krafft point. This paper outlines some results on the effect of the kinds of gegenions and chain length of surfactant on the Krafft point, surface tension, cmc, and solubilizing power in aqueous solutions of these perfluoroalkane carboxylates.


Experimental Method

Solutions of perfluoroalkane carboxylates with hydrocarbons of varying lengths were created.

To measure Krafft Point and CMC: Krafft point was determined by the abrupt increase in the electrical conductivity of as a function of temperature

Results

Surfactants form micelles above the Krafft point and the solubility of surfactants in water increases drastically. Therefore, solubilization occurs above the Krafft point. CMC: measured by the electrical conductivity-concentration curve at constant temperature





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