345 J. Cosmet. Sci., 73, 345–361 (November/December 2022) Address all correspondence to Qinghua Li, Qinghua.Li@momentive.com Silicone to Reduce Combing Force, Control Flyaway, Repair Damage in Transparent Shampoo* QINGHUA LI, SUSAN ZOU AND LINDA WEI Momentive Performance Materials Japan LLC, Kawasaki, Kanagawa, Japan (Q.L.) Momentive Performance Materials Inc., Shanghai, China (S.Z.) Momentive Performance Materials Inc., Guangzhou, China (L.W.) *This paper is a summary of a joint project with Beauty Hi-tech Innovation Co., Ltd., KIBC 604, 5-5-2 Minatojima Minamimachi, Chuo-ku, Kobe, Japan 650-0047. Accepted for publication January 19, 2023. Synopsis Currently in the beauty and personal care markets there is a megatrend of the natural and clean. Consumers relate a product’s clear appearance to being cleaner and potentially more natural regardless of the ingredients therein. Formulators continue to look for additives that can be incorporated into clear shampoos to provide superior conditioning. Traditional silicone conditioning agents can cause haze in these formulations. Formulators have attempted to remove silicones, resulting in a challenge to meet consumer needs especially for colored, permed, or damaged hair. In this paper, we have studied the performance of amodimethicone and silicone polyquaternium-18 microemulsion in transparent shampoos. The benefits evaluated were reduction in combing force and controlling flyaway while maintaining the shampoo’s transparency. In addition, hair breakage tests, tensile strength tests, digital microscope observations, and silicone deposition tests were conducted. The apparent hair damage repair was quantified for the amodimethicone and silicone polyquaternium-18 microemulsions in shampoo. We have found a good correlation between the silicone deposition data and performance. INTRODUCTION Repeated coloring, bleaching, and permanent-wave treatments result in damaged hair. This is especially true for the younger generation due to the increase in frequency of these events. These processes strip the 18-methyleicosanoic acid (18-MEA) content of the cuticle, rendering the surface of the hair hydrophilicity. Many attributes such as frizziness, roughness, and poor manageability are attributed to hydrophilicity of the hair. Silicones are known to increase the hydrophobicity of hair, thus reducing the appearance of damage and enhancing the sensorial attributes of the hair. Therefore, silicone has become a unique solution in the hair care category it is widely used for hair care products, in part due to its low surface tension. It can form a very uniform film on the hair shaft keep good alignment

346 JOURNAL OF COSMETIC SCIENCE of the hair shaft, resulting in smooth, shiny, and soft feel of the hair and enhance detangling and result in better combability of the hair (1,2). One class of silicone conditioning agents, amodimethicone (amino-modified dimethicone), is particularly useful for treatment of damaged hair. Amodimethicones impart a hydrophilic property while exhibiting a good affinity to the hydrophilic portions of the hair due to the NH 2 moiety. The use of amodimethicones drastically increased starting in the late 1990s and early 2000s. Certain consumers with highly damaged hair who used highly concentrated amodimethicone shampoos, conditioners, and leave-on treatments began to notice a buildup effect of the product. After repeated treatments the hair would become heavier with less volume. It was necessary for consumers to use shampoos frequently to keep their hair looking clean. The industry began to optimize the structure of the silicones in order to avoid this problem. Amodimethicone products that had lower amine content were developed. In addition, more advanced functional polymers with different molecular structures further enhanced the performance, which allowed the formulators to use less silicone and achieve the same benefits without buildup. Examples include bis-cetearyl amodimethicone (3,4) and amino-polyether-silicone block copolymer ([AB]n) (5) such as PEG-40/ PPG-8 methylaminopropyl/hydroxypropyl/dimethicone copolymer, etc. Another class of reactive silicones was also developed. Polysilicone-29 is a dispersion of a reactive silicone copolymer that can deposit on the hydrophilic portions of the damaged hair. Once deposited, polysilicone-29 cures, resulting in a durable hydrophobic coating on the hair. The hydrophobic coating allows for traditional conditioning agents to deposit better in rinse- off applications, resulting in reduction of friction and combing force and improved hair smoothness, resulting in improved and long-lasting hair manageability (6,7). Today’s consumer believes that transparent shampoo formulations provide a cleaner, less heavy feeling to the hair. Formulators that have removed the traditional silicones to improve clarity have discovered a significant impact on the sensory characters of the hair. In particular, the squeakiness, reduction in smooth feel, and manageability remain a challenge (8). In this paper we will discuss the approaches in which one can formulate transparent shampoos while maintaining the high level of performance of a silicone. Attributes of silicone emulsion such as particle size, amine content, charge density, and hydrophilic– hydrophobic balance are demonstrated to be critical to meet the needs of the consumer. We hypothesized that particle size of less than 100 nm was required to produce a transparent shampoo the amine content and charge density in a silicone molecule were needed to allow for efficient deposition from rinse-off applications and the proper balance of amine content, charge density, hydrophilicity, and hydrophobicity of a silicone molecule were needed to reduce the buildup effect, thus preventing weighing down the hair. We have developed two silicone microemulsion products (particle size 100 nm) to address the need for superior conditioning while maintaining clarity of the shampoo. Silsoft@ AM1021N PMF emulsion is a microemulsion of amodimethicone with a specific amine content. Silsoft@ Silk PMF emulsion is a microemulsion of a cationic amino-polyether-silicone block copolymer ([AB]n+), which contains amino groups, polyether chains, and cationic moieties in the polymer to balance the molecular hydrophobicity and hydrophilicity and control the deposition and buildup property. The molecular structures of amodimethicone and silicone quaternium-18 are illustrated in Figure 1. Properties such as manageability, lather performance, and combability, and the elimination of the perception of buildup were studied herein.