Application of Water-Holding Polymers as a Skin Moisturizer

Abstract

Some water soluble polymers formed “hydrogel” film containing water. This “hydrogel” film was expected to provide natural protective characteristic not found in commonly used low-molecular weight humectants. Film strength and elasticity tests on the polymers gave sodium hyaluronate the highest values under all test conditions.
In vivo tests, surface slip resistance measurement indicated that sodium hyaluronate significantly reduced skin friction resistance and thus increased skin smoothness.
Transepidermal water loss, and skin/polymer affinity measurements revealed that some water soluble polymers formed not a completely occlusive but a water-permeable, a dermal respirable film on skin surface.
In vitro and in vivo test results suggested that ideal water soluble polymers which would be useful as a skin moisturizer should meet the following conditions; (i) Should have a high molecular weight rather than a low molecular weight. (ii) Should have a component of N-compound for better skin affinity. (iii) Should have a distortion-structure to form a tough and flexible film on skin surface. Sodium hyaluronate having a molecular weight in 6×10⁵-9×10⁵ range fulfilled all of these conditions. The optimum combination of these properties is believed to enhance the shin's natural protective mechanism and is chiefly responsible for its outstanding performance as a skin moisturizer. It was confirmed further that lotions containing sodium hyaluronate had pleasant skin feel and was perceptible at a low level of incorporation by the consumers.