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J. Cosmet. Sci., 60, 261–271 (March/April 2009) 261 Infl uence of functionalized silicones on hair fi ber–fi ber interactions and on the relationship with the macroscopic behavior of hair assembly ANNE DUSSAUD and LARA FIESCHI-CORSO, Momentive Performance Materials, 769 Old Saw Mill River Road, Tarrytown, NY 10591. Synopsis It is well established that silicones alter hair surface properties and that silicones have a signifi cant impact on the macroscopic behavior of hair assembly, such as visual appearance, combing performance and manageabil- ity of the hair. In order to fi ne-tune the chemistry of functionlized silicones for specifi c consumer benefi ts and hair types, we investigated the infl uence of silicones on hair fi ber–fi ber interactions and their correlation to hair volume. The incline plane fi ber loop method, implemented with a high-precision motorized rotary stage, was used to quantify the fi ber–fi ber interactions. Low load static friction was studied as a function of polymer molecular weight, dose and chemical architecture. This information was related to the macroscopic behavior of hair assembly, using virgin curly hair in high humidity. INTRODUCTION Hair assembly behavior is driven by geometrical factors, mechanical properties and the local interactions between fi bers. Although conditioning polymers primarily affect local interactions between fi bers, a clear understanding of the role of polymers on fi ber/fi ber interactions is lacking. In a recent study, Bushan investigated, at a very fi ne length scale using AFM technique (1), hair surface treated with conditioners. These measurements displayed evidence that conditioners accumulate along the edge of cuticles and increase the adhesive force between the AFM tip and the hair substrate. The magnitude of this adhesive force was attributed to the capillary force created by the conditioner fl uid material on the AFM tip and, there- fore, scaled with the size of the probe. Earlier, an elegant method, which consisted of measuring the sliding angle of a single hair loop on two parallel fi bers (2–3), was developed to measure fi ber–fi ber interactions. In this technique, the contact area is the intersection of two cylindrical hair fi bers, crossing perpendicularly. The technique measures frictional and adhesive forces in the range of μN. In addition to its simplicity, the hair loop measurement technique presents several advantages: