| Abstract: | The natural log of critical micelle concentration (CMC) values obtained from the natural log discontinuities in surface tension-concentration relationships, through the least-squares regression analysis, were plotted against the respective hydrophile-lipophile balance (HLB) values of four groups of ethoxylated octylphenol-, dodecylphenol-, tetradecylphenol- and hexadecylphenol-formal-dehyde polymeric surfactants. The obtained HLB-CMC relationship for the investigated compounds can be represented satisfactorily by the linearized equation In (CMC) = a—b (HLB). Values of the two constants a (intercept) and b (slope) for 16 of these compounds were determined at 28, 38, 48 and 58°C, using the least-squares regression analysis of data. The study revealed that both a and b values increase with increasing number of carbon atoms in the ethoxylates of polymeric compounds having a linear alkyl chain. The influence of branching is reflected in the values of a and b of the compounds having a branched dodecyl chain. The most striking feature of the obtained equation is that the CMC decreases with increasing HLB (negative slope). This observation is contrary to what is generally expected for both ionic and nonionic surfactants. |
