Chameleonic Cosmetics: Developing Innovative Photochromic Polymers and Macromolecules

Polymers are widely used in cosmetic products thanks to their range of applications leading to high-performance products.1 Film-forming polymers are strategic to create a homogeneous film after the evaporation of the volatile components, extending the permanence of make-up including colour and properties. In this context, linking dyes to the polymers enhances this feature. Furthermore, as the interest in having new effects in makeup is growing, we started to explore non-static dyes, exploiting photochromism. Photochromism is defined as the light-induced reversible transformation of a molecular entity into one or more isomeric species that possess different absorption spectra.2 The first technology that uses this photochromic feature is reported in a patent in which a photochromic spiropyran is chemically linked by transesterification to a silicon cosmetic oil with film-forming properties.3 This innovative photochromic cosmetic oil switches from transparent to blue, providing an intense colouration of make-up when exposed to UV light. Silicones acceptance in cosmetic formulations is becoming questioned due to limited biodegradability with potential bioaccumulation.4 Therefore, it is necessary to replace silicones with other film-forming polymers. We show how it is possible to synthesize by condensation bio-based film-former polymers, as polyesters or polyurethane, capable of transesterification with photochromic targets appropriately engineered. We selected T-type photochromic dyes able to return to the original form by removing UV light, having a range of colours across the visible spectrum to build a trichromic cyano, magenta and yellow system. A naphtopyran-based structure was chosen for magenta and yellow, while, for blue, spirooxazine and cyano spiropyran. All these targets can efficiently undergo transesterification, so it is possible to link the molecule to the polymer, both as a terminal (Figure) or as a linker between two different OH groups. References 1. Patil, A.; Ferritto, M. S.; Polymers for Personal Care and Cosmetics, 2016, (Chapter 1). 2. Towns, A.; Physical Sciences Reviews, 2021, vol. 6, (pages 477-511). 3. Galotto, N.; US20230094852A1, 2020. 4. Goussard, V., Aubry, J., Nardello-Rataj, V.; Advances in Colloid and Interface Science, 2022, Volume 304, (102679).