Hair consists of many long protein chains composed of amino acid building blocks. These chains, or polymers, are bound to each other via 1) hydrogen bonding, 2) salt bridges between acid and base groups, and 3) disulfide bonds. Water reversibly cleaves the hydrogen bonds. This makes wet hair easy to shape and set. When the water evaporates, hydrogen bonds form at new positions, holding the hair in this set. In strongly acidic solutions, such as where the pH is 1.0 to 2.0, both hydrogen bonds and salt bridges are broken. The disulfide bonds, however, can still hold the protein chains together in the strand of hair under such conditions.
At a slightly alkaline pH of 8.5, some disulfide bonds are broken (Dombrink et al., Chem Matters, 1983, page 8). Repeated washing with slightly alkaline shampoo damages the hair by breaking more and more of the disulfide bonds. This causes the cuticle or outer surface of the hair strands to become ruffled and generally leaves the hair in a wet, tangled, and generally unmanageable state. This is one cause of “split ends.” Once the hair dries, it is often left in a dry, rough, or frizzy condition. Additionally, rough hair catches light unevenly and makes the hair look lusterless and dull. The hair can also be left with increased levels of static upon drying, which can interfere with combing and result in a condition commonly referred to as “fly-away hair.”
Disulfide linkages are also ruptured due to heating or use of various reducing treatments. Current compositions and methods for waving and straightening mammalian hair use reducing agents such as thioglycolic acid, particularly as the ammonium salt, to cleave the hair's cystine disulfide bonds. Once the disulfide bonds are broken, and the hair is placed in stress to establish the final style (e.g., straight, wavy, or curly) the disulfide bonds are reestablished. Oxidation to restore the reduced bonds can be achieved by simply exposing the hair to atmospheric oxygen, but this oxidation step is very slow and is of very little practical use. Generally, hydrogen peroxide or sodium bromate is used as the oxidizing agent. However, the newly formed disulfide bonds are under stress to maintain the hair's new shape, thus, they break easily resulting in a reversion of the hair style over time. In addition, the use of peroxides in the hair styling process can result in damaged hair, removal of non-natural color from the hair, and/or leave the hair frizzy. Furthermore, some latent free thiols may remain in the hair even after oxidative treatment.
Treatment with peroxides used in the hair styling process results in the following reaction:2K—S—H+H2O2→K—S—S—K+2H2O  (Rxn I)where K represents keratin in the hair. However, if two K—S—H groups are not present for the reaction (Rxn I) to take place, it is believed that the following reaction takes place, which results in damaged hair.K—S—H+3H2O2→K—SO2—OH+3H2O  (Rxn II)
Keratin is also a major component in skin. Damage to the disulfide bridges of keratin can cause skin to look unhealthy or flaky. Maintaining the disulfide bridges of keratin keeps the skin healthy and prevents cracking and splitting.
A variety of approaches have been developed to alleviate these problems, including post-shampoo application of hair conditioners, such as leave-on and rinse-off products. Typically, conditioning rinses put back the oily coating, especially to the damaged portion of the hair where the cuticle has become ruffled since conditioners cling best to these portions. However, too much or too heavy a conditioner will make the hair stickier, thus attracting dirt and often may make more shampooing treatments necessary. Typically conditioners do not bind the free thiols in hair.
The use of cationic polymers to form coacervates to provide conditioning benefits to the hair is known, such as described in International Published Applications WO 93/08787 to King et al. and WO 95/01152 to Napolione et al. Commonly used cationic deposition polymers include natural polymers, such as guar gum polymers, that have been modified with cationic substituents. The selection of a cationic guar polymer with sufficient charge density and molecular weight results in sufficient deposition of conditioning agents when incorporated in a shampoo or body wash. However, a relatively high level of such cationic guar polymer generally must be deposited on the hair or skin. Moreover, the cost of such cationic guar polymer is relatively high. As a result, incorporation of cationic guar polymer can increase the manufacturing costs of such shampoo compositions. Additionally, these shampoo compositions typically are useful for wet hair conditioning, but are not capable of delivering satisfactory dry hair smooth feel. Furthermore, these conditioners do not bind the free thiols in hair.
U.S. Pat. No. 5,656,265 to Bailey et al., discloses a hair styling conditioning process for use after treating the hair with a reducing agent. The process involves contacting the hair with a compound having an electrophilic group and at least one hydrophobic group. According to Bailey, the electrophilic groups react with the thiol groups to provide a plurality of hydrophobic groups on the hair. However, these conditioners do not bind the free thiols in hair together.
There is a need for hair formulations and treatments that can provide improved conditioning benefit for hair. Specifically, there is a need to provide long lasting moisturized feel, smooth feel, and manageability control to hair when it is dried. There is also a need for hair formulations and treatments that repair latent free thiols in the hair.
There is a need for hair formulations and treatments that repair and/or strengthen damaged hair and rebuild stronger bonds in hair treated with reducing agents.
There is also a need for skin formulations and treatments that provide improved conditioning and/or moisturizing benefit to the skin. In particular, there is a need to provide a long lasting moisturized and smooth feel to the skin. There is also a need for skin formulations and treatments that repair free thiols in the skin.
Therefore, it is an object of this invention to provide improved compositions and methods for repairing and/or strengthening damaged hair.
It is also an object of this invention to provide compositions and methods for using these compositions that repair and/or strengthen hair after a washing or reducing treatment.
It is also an object of this invention to provide compositions and methods for conditioning, moisturizing, and/or otherwise treating the skin.