Without wishing to be bound by theory, it is believed that the one or more linkers of the first composition, e.g. O,O'-Bis(3-aminopropyl)diethylene glycol can cross-link the carboxylic acid groups of the hair proteins as the hair proteins are made up of amino-acids, by forming hydrogen bonds or ionic bonds. When the F-layer has been removed due to perhydrolysis, the one or more linkers of the first composition can also interact with the sulfonate groups of the epiticule layer by forming ionic bonds or hydrogen bonds. The one or more linkers of the first composition may also cross-link the sulfonate groups of the cysteine amino acids of the hair proteins. Similarly, it is also assumed that the one or more electrophile ingredients of the second composition, e.g. maleic acid can cross-link the amino groups of the hair proteins by forming ionic bonds or hydrogen bonds. The one or more electrophile ingredients of the second composition, e.g. maleic acid may also cross-link the sulfonate groups of the cysteine amino acids of the hair proteins by forming hydrogen bonds. The effective amount of available amino groups and carboxylic acid groups inside the hair is unknown.
Hence, it is believed that the first composition comprising one or more linkers and the second composition comprising one or more electrophile ingredients of the present invention need to be applied sequentially such that they do not form relatively stable complexes prior to reacting inside the hair.
Hence, the one or more linkers can possess one or more substituents that is able to form an ionic bond or a hydrogen bond with a group of an amino acid such as a carboxvlic acid or an amino group. Also, the one or more linkers can possess one or more substituents may be able to form an ionic bond or a hydrogen bond with another group comprised in a typical damaged hair such as a sulfonate group or a thiolate group.
Hence, especially when the one or more linkers may possess one or more amino groups, preferably one or more terminal amino groups, the one or more linkers, can form an ionic bond or a hydrogen bond with either the available carboxylic group of the amino acids of the hair proteins and/or the sulfonate groups available on the epiticuie surface, or the sulfonate groups of the oxidized cysteine amino acids of the hair proteins.