Surfactants

For polymetric materials without definitive hydrophobic and hydrophilic regions, the __ energy is critical to generation of steric repulsion. The __ energy should neither be so low as to result in no polymer adsorption nor so high as to result in complete polymer adsorption to the droplet

adsorption

Emulsions made with __ soap emulsifying agents sometimes require the addition of auxiliary emulsifiers for stable solutions

alkali

-Soaps with an organic __ as the cation are more balanced and less hydrophilic and form more stable emulsions than the alkali soap emulsifiers

amine

Surfactants are __, meaning they have water-loving and a water-fearing structures

amphipathic

A(n) __ surfactant frequently used in pharmaceutical dosage form is Lecithin NF, a complex mixture of phosphatides, mainly phosphatidyl choline

amphoteric

cationic surfactants do not make good emulsifiers but are useful as __ agents

antimicrobial

__ surfactants are quaternary ammonium compounds, suh as benzalkonium chloride, benzethonium chloride, and cetylpyridinium chloride they are very water soluble

cationic

for nonionic surfactants: the temperature at which a product becomes turbid when heated

cloud point

At the point where surfactant molecules form micelles, the concentration at which this happens is called the __ __ __

critical micelle concentration

the minimum temperature at which micelles form

critical micelle temperature

__ these are salts of alkyl sulfates, sulfonates, phosphates, and sulfosuccinates They are __ soluble

detergents, water

Although emulsifying agents must contain both hydrophilic and lipophilic parts, neither portion may be too strongly __ -For example, if the hydrophilic part of the molecule is completely __, the substance does not concentrate at the water-oil interface, it remains dissolved in the water phase

dominant

A(n) __ agent is a compound that concentrates at the interface of two immiscible phases, usually an oil and water

emulsifying

Surfactants orient themselves at interfaces so as to reduce the interfacial free __ produced by the presence of the interface

energy

The emulsifier must produce a stable __ at the interface -Must be strong enough to prevent coalescence of dispersed droplets

film

__ soaps -These are salts of fatty acids in which the positive ion is divalent or trivalent (Ca2+, Mg2+, Zn2+, Al3+) -They are __ soluble

hard, oil

Soaps are incompatible with __ concentrations of electrolytes and with __-molecular-weight cations such as the preservatives benzalkonium chloride and benzethonium chloride. The anionic portion of the soap binds these preservatives and renders them inactive

high

the temperature at which all three detergent phases (crystals, micelles, and monomers) exist at equilibrium

kraft point

-artificial phospholipid vesicles with size between 50 nm to >1 mcm -microvesicles composed of one or more bilayers of amphipathic lipid molecules enclosing one or more aqueous compartments -Can incorporate hydrophilic drugs in the inner aqueous compartments and/or hydrophobic drugs in the lipid bilayers -easily uptaken by cells

liposomes

Surfactants __ the surface tension between a liquid and a gas or the interfacial tension between two liquids

lower

__ are structures similar to liposomes but do not have an inner liquid compartment

micelles

__ is afforded both by mixing interaction (__ repulsion) and entropic interaction (__ restriction)

osmotic, volume

Two major sources of __ are egg yolks and soy beans

phosphatides

__ hydrophilic surfactants that tend to form o/w emulsions -tweens -spans -sorbital -highly viscous, yellowish liquids

polysorbates

because the ionic centers of detergents __ each other, detergents do not form firm, intact barriers. These surfactants are most often used in conjugation with secondary nonionic emulsifiers such as cetyl or stearal alcohol

repel

__ soaps -these are salts of fatty acids in which the positive ion is univalent, such as Na+, K+, and NH4+.The most common fatty acids are stearic (C-18), palmitic (C-16), and lauric (C-12) -Soaps with an organic amine as the cation are more balanced and less hydrophilic and form more stable emulsions than the alkali soap emulsifiers -Emulsions made with alkali soap emulsifying agents sometimes require the addition of auxiliary emulsifiers for stable emulsions

soft

If a surface active agent isn't strong enough alone to create a strong film in an emulsion, a __ must be added

stabilizer

__ repulsion: may be produced using nonionic surfactants or polymers, such as polyvinyl alcohol or poloxamers

steric

Surface-active agents, also called __, are molecules or ions that are adsorbed at interfaces

surfactants

Soft soaps are __ emulsifiers for internal-use emulsions because of their soapy taste and laxative action

unsuitable

-Water-soluble polymers favor o/w emulsions. -They have the advantage of being __-building agents in addition to having surface activity -With the exception of some of the natural gums, most of the water-soluble polymers are used as auxiliary emulsifying agents

viscosity

Soft soaps are __ soluble

water

__-Soluble Polymers Natural polymers (polysaccharides) -acacia, agar, pectin, sodium alginate, xanthan gum, tragacanth, polypeptides, such as casein and gelatin -Cellulose Derivatives -Synthetic Water-Soluble Polymers -polyvinyl alcohol, povidone, carbomer, polyethylene glycols

water