Surfactants
Emulsifier
(Emulgent or a surfactant) a stabilizing agent in emulsions
amphipathic
A molecule that has both a hydrophilic region and a hydrophobic region.
Describe the features of the surfactants opposing forces.
A surfactant has at least 1 polar and 1 nonpolar force The results of the opposing forces within the same molecule are adsorption and aggregation In aqueous media, surfactant molecules will migrate to air/water and solid/water interfaces, to minimize contact with their hydrophobic surfaces as much as possible.
What are the physical properties of surfactants?
Adsorption, Emulsification, Suspension, and Foaming
Surfactant Structure
All surfactants are characterized by having two regions in their molecular formula. (amphipathic)
what are the four typical surfactants?
Amphoteric (zwitterionic), Anionic, Cationic, and nonionic.
What is a zwitterionic structure?
An amphoteric structure that is composed of an amine and a carboxylate group that is capable of being positive and negative.
Hydrophile-Lipophile balance (HLB):
Based on surfactants that are considered to be composed of both hydrophilic and lipophilic groups. The range is generally placed between 0-40 to determine whether the dominate substance has more of an affinity for water or for oil. For a substance that is x>10, it is considered hydrophilic. For a substance that is x<10, it is considered lipophilic with an affinity for oil.
What are two factors of surfactants?
Critical Micelle Concentration (CMC), and Hydrphile-Lipophile Balance (HLB)
Give examples of Cationic Surfactants:
Dodecyl Trimethyl Ammonium Chloride
What are 4 physical properties of surfactants?
Emulsification, Suspension, Foaming, & Adsorption
Give examples of amphoteric Surfactants:
Natural Soaps (alkyl carboxylates), betaines, and lipids.
Name a couple of applications for surfactants?
Paint, anti-fog, shampoo, toothpaste,oil dispersion, wetting, ski-wax, foaming, defoaming, hair conditioner etc...
Give examples of anionic surfactants:
Sodium Dodecyl Sulfate (SDS), Sodium Oleate, and Sodium Stearate.
What are surfactants
Surface-active-agent or substances that absorb to surface or interfaces, causing a marked decrease in the surface tension.
What happens when you place an amphipathic molecule into oil?
The head which is hydrophilic is insoluble in oil; thus it will have high energy due to low surface tension. The tail that is soluble in oil will be attracted to the oil; thus it will have a lower energy. (Draw an example)
What happens when you place an amphipathic molecule into water?
The head which is hydrophilic, is soluble and the tail which is hydrophobic is insoluble; thus, the hydrophilic head will have low energy due to high surface tension and the tail will have high energy due to low surface tension. Draw an example
Surface Tension
The molecules at the surface do not have other molecules on all sides of them and therefore are pulled inwards. This creates some internal pressure and forces liquid surfaces to contract to the minimal area
Give examples of nonionic surfactants:
Tween, Span, Polyoxyethylene and Pluronic
Softner
Used to prevent static clinging
Does the length of the (CH2)n determine the solubility? How? Demonstrate the effect for an amphipathic molecule in water and in oil.
Yes, the length of a (CH2)n does determine solubility. If you increase the length of a chain (hydrophobic) on that is on an alcohol or carboxylic acid hydrophilic head group, and submerge it in water the solubility of the structure will begin to decrease. If the same structure is placed into an oil, the substance will be soluble to the (CH2)n chain thereby increasing it.
interface
a boundary between two phases
Detergent
a compound or mixture intended to assist with cleaning. This term is used often for soap or other cleaning supplies.
Amphoteric
a substance that can act as both an acid and a base (composed of both '+' and '-' charges.)
Adhesive
a substance that unites or bonds surfaces together
hydrophobic tails
composed of hydrocarbons that have no affinity for water
Hydrophilic head
contain alcohol group that has an affinity for water group
nonionic
contains no charge i.e--> polyhydric alcohol(tween & Span), polyoxyethylene, pluronic (poloxamer), sucrose esters (SE)
CMC
critical micelle concentration (very low concentration of micelle) - Concentration of Surfactant which begins to grow micelles
ionic
either can be cationic or anionic
lipophilic head
group containing the alcohol
What are the two surfactant features in water?
hydrophobic and hydrophilic.
ink
is a liquid containing various pigments or dyes to color surfaces.
micellisation
is the aggregation process
Give three different types of interfaces, the system type and Product examples.
solid-liquid -> suspension -> sand in water liquid-liquid -> Emulsion -> milk, cream liquid-vapor -> Foam -> shaving cream
surface area
the sum of all the areas of all the shapes that cover the surface of the object.
