Shampoo and Conditioner Science 92 surfactant micelles are responsible for irritation of skin and eyes and that binding of the surfactant to the polymer effectively reduces the concentration of free micelles. A measure of mildness is the delta CMC, which is defined as the difference between the CMC of the surfactant alone and the higher CMC of the surfactant in the presence of polymer. Larger values of delta CMC for a particular surfactant are apparently correlated with lowering of the irritation potential. The delta CMC provides a measure that is useful for selecting, comparing and optimizing polymers that reduce the irritation potential of selected surfactant systems. Carbomer and acrylates copolymer have been identified as polymers that exhibit a satisfactory delta CMC. Conditioning Shampoos Today’s conditioning shampoos are expected to confer the wet hair attributes of hair softness and ease of wet-combing, and the dry hair attributes of good cleansing efficacy, long-lasting moisturized feel, and manageability with no greasy feel. The origin of conditioning shampoos can be traced to the balsam shampoos of the 1960s followed by the introduction of Polyquaternium-10 by Des Goddard38,39 in the 1970s and 1980s in which he introduced the concept of polymer-surfactant complex coacervates that phase-separate and deposit on the hair during Figure 15. Plot of surface tension vs. surfactant concentration for surfactant alone and for surfactant in the presence of polymer. The difference in the CMC induced by the presence of the polymer is claimed to be related to the effect of the polymer in enhancing the mildness of a shampoo.