Liquid Crystal in Cosmetics emulsions

Introduction:Lipids in the SC are organized in a bilayer LC-like structure.

Skin dryness is prevented by keeping liquid like nature of the bilayers.

Moisturising agents are required to improve skin hydration and increase water retention.

Lamellar LCs are good candidate.

What are the components of the LC base?

a Fatty surfactant: GMO, long chain alcohols,..(too lipophilic to stabilize o/w emulsion alone)b high HLB surfactant.

What is the phases produced when dispersing a or b in water separately and combined ?

a too hydrophobic to form swollen lamellar phaseb forms only micelles

a and b >gel structure (b penetrates the layers of a and permits swelling and lamellar liquid crystal formation)

Heating followed by cooling >> lamellar crystalline gel network

Figure: In a system of water, ionic surfactant, and long-chain alcohol three phases are important cosmetically.The aqueou solution (lower left) contains spherical micelies, the lameliar liquid crystal is located in the middle, and the alcohol solution (top) contains inverse micelles.J. Soc. Cosmet. Chem., 41, 155-171 (May/June 1990)

How does the lamellar LC phases form? At optimum blend of a and b.

Suggested structure for the

lamellar LC (at T>Tk)

Suggested structure for the lamellar gel phase (at T<Tk)

Advantages of the LC phases:

• emulsion definition: “An emulsion is a mixture of two liquids, one of which is dispersed in the other in the form of liquid droplets and/or as liquid crystals”

• emulsion stability,

• Prolong hydration properties,

• Controlled drug delivery,

• Easy to formulate,

• Well-liked skin feel.