In a recent article published in the journal Materialsthe researchers reviewed the literature and patents on the use of polyhedral oligosilsesquioxanes (POSS/SSQ) and their derivatives as constituents in the cosmetics industry. The review also addressed production strategies for these chemicals.
To study: Silsesquioxanes in the cosmetics industry — Applications and prospects. Image Credit: Vladimir Zotov/Shutterstock.com
The growing demand for creative and effective personal care products is prompting manufacturers to develop new formulas that will meet the needs of their customers. When producing new cosmetic products, various factors must be considered, including appearance, rheology, consistency, ease of removal, and function. Over the years, silicones have garnered considerable attention in modern cosmetics due to their varying solubility and distinct properties.
General diagram of the different categories of silsesquioxane: (a) random (T-resin, polysilsesquioxane); (b) ladder; (vs) T-series cage; (D) homosilsesquioxane; (and) double-decker bus; (F) disilanol; (g) trisilanol; (h) tetrasilanol. Image credit: Olejnik, A et al., Materials
Among the various silicones, silsesquioxanes have gained popularity in the cosmetic sector in recent years. These chemicals have been proposed for use as emollients, dispersants and viscosity modifiers in new cosmetic formulations. A specific POSS present in a formulation could provide solubility or compatibility advantages.
However, there are few reports available in the literature that discuss the usefulness of POSS derivatives in cosmetics. Moreover, an in-depth review of patents related to the use of silsesquioxanes in cosmetic formulations is still lacking.
About the study
In the present study, researchers investigated the macromolecular and molecular structures of various POSS derivatives and their polymer hybrids. After a brief overview of the structure and nomenclature of POSS, many synthetic techniques of silsesquioxanes, such as hydrolytic (oligo) condensation and corner capping, were discussed. Further, the preparation of silsesquioxane/polysilsesquioxane resins by strong acid or base catalyzed hydrolysis and polycondensation of alkoxysilanes has been elucidated.
Additionally, post-functionalization of the POSS cage via catalytic and non-catalytic modifications of silsesquioxane systems has been illustrated.
An extensive literature review was performed to analyze patent applications relating to the use of silsesquioxanes in cosmetic and personal care formulations. The importance of silsesquioxanes as an ingredient in cosmetic products has been assessed. The multitude of applications and multifunctionality of POSS chemical compounds have been explored.
Various silsesquioxane derivatives dedicated to personal care have been presented as examples. Applications of POSS derivatives in color cosmetics, nail care, hair care, and skin care products have also been demonstrated. Furthermore, the future prospects of polysilsesquioxanes and their derivatives in the cosmetics industry were discussed.
An open-cage silsesquioxane trisilanol wedge capping procedure; (a)-a product of silanol groups capped with monochlorosilanes; (b)—a cage T8 true corner overlay product with trichlorosilane. Image credit: Olejnik, A et al., Materials
In this review, researchers observed that polysilsesquioxanes and polysilsesquioxane resins were the most common structural forms in patent applications related to the field of silsesquioxanes/cosmetics and silsesquioxanes/personal care for the year 1990-2021. In cosmetic compositions, these forms were much more common than structurally pure polyhedral forms.
Discoveries subject to intellectual property protection in major international markets from 2000 to 2020 were led by L’Oréal (nearly 30% of all patent applications). Kose Corp. was in second place with more than 8%, followed by Henkel with 4% and The Procter & Gamble Company with 3%. Japanese companies such as Shiseido Nippon Fine Chemical, Kao and Sinopec have also used SSQ.
The increase in the number of patent applications was linear and did not exceed 10 to 20% on an annual basis between 2005 and 2020. The impact of the epidemic on the drop in the number of reports in 2020-2021 has also been visible.
According to detailed analyzes of the content of applications, silsesquioxanes appear to play a role similar to functional polysiloxanes; however, they differ from polysiloxane analogs due to the higher equivalent of functional groups per unit mass and the condensed and nonlinear nature of their structure.
Furthermore, based on the detailed review of numerous studies, polysilsesquioxanes and their various hybrids, such as polysilsesquioxane-siloxane resins or copolymers, have been shown to be an acceptable choice for both cost-effective and high-performance cosmetic formulations.
Several patent applications in the area of silsesquioxanes/cosmetics and silsesquioxanes/personal care (based on the Google Patents database). Image credit: Olejnik, A et al., Materials
In conclusion, this review elucidates the use of silsesquioxanes in cosmetics which was first reported in the late 1960s and early 1970s. However, the cosmetics industry only experienced a boom in mid-1990s, and this boom was caused by the rapid growth and increasing importance of cosmetics in the global market.
The boom has also been attributed to extensive research into the influence of SSQs on complex systems including water-based media, emulsions, polymers, and other materials, which has led to their widespread use of SSQs. Economic factors and rapid advances in this field have facilitated the use of this group of chemicals in the cosmetics and personal care industry.
Overall, this review highlights that polysilsesquioxane structures have substantial advantage in practical applications, as evidenced by various studies and patents that provide data on a variety of characteristics, including film and color stability, UV protection, coating strength, etc.
This could be attributed to the significant difference between the manufacturing cost of disordered structures and molecular molecules. The authors believe that the modeling of functional characteristics, the minimization of production costs and the development of multifunctional polysilsesquioxanes are the goals of future research on the use of silsesquioxanes in the cosmetic sector.
Olejnik, A., Sztorch, B., Brzakalski, D. et al. Silsesquioxanes in the cosmetics industry – Applications and perspectives. Docs 15(3), 1126 (2022). https://www.mdpi.com/1996-1944/15/3/1126