Oxyethylated fatty alcohols

Twelve oxyethylated fatty alcohols with various lengths of alkyl chain and ethylene oxide were used in this investigation. In view of numerous literature data available, physicochemical tests were limited to measurements of surface tension, wettability and viscosity. Microscope photographs were taken in polarized light in order to confirm the appearance of liquid crystalline structures. As expected, formation of micelles was observed at low concentrations, whereas mesophases (hexagonal and lamellar) were identifled at concentrations of about 50% to 70%. 

Aqueous Solutions of Oxyethylated Fatty Alcohols as Lubricating Substances 343... 

In the REO notation used here, R is the alkyl chain with n carbon atoms in the chain, while EO , is the number of moles (m) of the combined ethylene oxide (EO). As a result of oxyethylation, fatty alcohols become amphiphilic, where the ethylene oxide chain is the hydrophilic part and the alkyl chain is the hydrophobic part. The general formula and a spherical model of lauryl alcohol oxyethylated with 3 moles and 5 moles of ethylene oxide are presented, respectively, in figs. 17.2 and 17.3. Using fig. 17.3, it is possible to geometrically estimate a relative proportion of the hydrophilic part (ethylene oxide chain) and of the hydrophobic part (alkyl chain) in the oxyethylated alcohol molecule. 

The solubility of oxyethylated fatty alcohols results from the formation of hydrogen bonds between water and a free electron pair on the oxygen atom of the ether group. The dehydration process connected with an increase in the temperature of the solution is important from the point of view of application, e.g., in tribology. Above a certain temperature, called the cloud point, hydrogen bonds are broken, and the compound loses its amphiphilic properties. As a result of desolvation, alcohol relatively increases its hydrophobic properties. These observations can be confirmed by the decrease in the critical micelle concentration (CMC) values with increasing temperature [27-31]. The dehydration process is reversible and, with a decrease in temperature, repeated hydration of molecules may occur at a certain temperature, called the clear point. Both the cloud point and the clear point depend on the structure of the compound, particularly on a relative proportion of the hydrophilic and hydrophobic parts [32-38]. 

TRIBOLOGICAL PROPERTIES OF AQUEOUS SOLUTIONS OF OXYETHYLATED FATTY ALCOHOLS... 

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