Types of Surfactants

Study Notes

Hydrophilic part carries no charge
Derive polarity from having an oxygen-rich portion of the molecule at one end and a large organic molecule at the other end
Oxygen component is usually derived from short polymers of ethylene oxide or propylene oxides

Positively charged molecules usually derived from nitrogen compounds
Not commonly used as cleaning agents in hard surface cleaners
Many cationic surfactants have sanitizing properties that are useful in creating disinfectants that leave a cationic disinfectant film on the surface

Change their charge with pH
Can be anionic, nonionic, or cationic depending on the pH
Charge of the hydrophilic part is controlled by the pH of the solution
Can act as anionic surfactants in an alkaline solution or cationic surfactant in an acidic solution
Usually, any one amphoteric can be any two of the three charge states

Definition: Self-assembled little spheres formed when surfactants are added to water, with hydrophilic head facing out and hydrophobic tail pointing in
Made out of amphipathic molecules
Can form in polar or non-polar liquids
Formed because only one end of the amphipathic molecules is compatible with the liquid

In aqueous systems, high interfacial energy between water molecules and hydrocarbon chains of the surfactant is the primary factor
In non-polar systems, attractive interaction between polar parts serves as the force governing the association process
Critical micellization concentration (CMC) is the concentration of surfactant at which micelles first form in solution or the concentration above which micelles will form spontaneously
Higher the concentration, the more micelles there are
Micelle formation is also dependent on the Krafft temperature, which is the temperature at which surfactants will form micelles
The hydrophobic effect is also a driving force that needs to be taken into account
Micelle formation can be summed up by thermodynamics, driven by entropy and enthalpy