50 HAIR CARE
post-dust exposure. Hair tresses washed with APTAC/ACM shampoo, produce significant lower combing work, which means APTAC/ACM could also provide anti-dust benefit, besides anti-pollution property.
Mechanism of APTAC/ACM for pollution protection Liquid crystal shampoo APTAC/ACM copolymer is a water-soluble polymer with high cationic charge density. It has an ability to form lyotropic liquid crystals with anionic surfactants in shampoo systems. The colloidal particles are negatively charged, surrounded by monolayer of unbounded anionic surfactants supporting the stability of the particles. Liquid crystals can be studied using an optical microscope. Figure 6 shows an image of liquid crystal shampoo formed by APTAC/ACM and anionic surfactants, heated up to 90°C. Liquid crystal particles remain stable during the dilution when the shampoo is lathered and applied on hair. Deposition of the particles on hair occurs via filtration and Van der Waal forces. Once the hair is rinsed, the unbounded surfactant is removed, cationic APTAC/ACM polymer inside particles will attach to the highly damaged negatively charged hair surface, and leaving the hair with an excess positive charge.
In Situ Controlled Flocculation (ISCF™) mechanism
Common cationic polymers are soluble in Stage 1 (During Conditioner Application) N-DurHance™ N-DurHance™ N-DurHance™ N-DurHance™ N-DurHance™ N-DurHance™ A-1000
(+ve charged) in Conditioner
Figure 6: APTAC/ACM forms lyotropic liquid crystals with anionic surfactants (optical microscopy image).
the undiluted shampoo but become insoluble during the massage and rinsing stage, the polymer surfactant complex precipitates out of solution and deposits onto the hair through the coacervation process. The deposition mechanism of APTAC/ ACM is totally different from common cationic polymers. When APTAC/ACM attached to the hair surface, the positive charged polymer will trap more anionic surfactants (SLES), and start to form flocculates on the hair surface (in situ).
During flocculate formation,
hydrophobic lauryl groups from SLES coat the hair surface, creating a homogenous hydrophobic layer on the hair surface.12 Asian bleached hair, pre-treated with
APTAC/ACM, is immersed in water and 4% SLES solution. The optical microscopy images were captured in wet stage. As showed in Figure 8, APTAC/ACM could form a homogenous complex gel layer with SLES on hair fibre surface, while no layer was formed when APTAC/ACM exist on hair alone. When this layer was dried, the hair surface will become hydrophobic since the hydrophobic lauryl groups of SLES turn
Hair Fiber (–ve charged)
Figure 7: The mechanism of in situ controlled flocculation ISCF™. PERSONAL CARE ASIA PACIFIC November 2019
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