+44 1625708989Characterization of intercalation compounds of sunscreens in a bentonite organoclay
Author(s): Camila Braga Dornelas1,2*, Katyane Rodrigues1, Miguel Ã?Æ?Ã?â??ngelo Santos Pinheiro-Segundo1, Rafael JosÃ?Æ?Ã?© Ribeiro Padilha1, Gardenia De Sousa Pinheiro3, Alejandro Pedro Ayala3 and Nereide Stela Santos-MagalhÃ?Æ?Ã?£es1Sunlight, especially UV radiation, is known forits beneficial effects, but even more for its harmful ones. As a result, the use of sunscreen preparations have been growing recently, which has led to their efficacy and safety being a current topic of investigation. The aim of this work was to obtain intercalation compounds of UVA avobenzone (AVO) and UVB ethylhexylmethoxycinnamate(EHMC) sunscreens and an organophilicbentonite (OB), in which the sunscreens were chosen because of the problems associated with their use, and the clay for its already described capacity to act as a physical sunscreen. The intercalation compounds (AVO-OB and EHMC-OB) were obtained by a solution technique and characterized using transmission electronic microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRPD) and thermal analyses (TG/DSC). The basal spacing data of OB was maintained in both. Furthermore, the TEM micrographs of both corroborate the XRPD results. Thermal analysis confirmed the formation of intercalation compounds with the disappearance of the melting point peaks of the sunscreens. Moreover, the concentrations of sunscreens in AVO-OB and EHMC-OB were quantified, at around 1% and 3%, respectively. These data account for the FTIR bands of the guest molecule overlapping those of the clay. All these findings demonstrated the intercalation, in a simple process, of AVO or EHMC in the layered structure of bentonite. The investigation of these nanocomposite systems on the preservation of the sunscreen properties in order to enhance the SPF and avoid sunscreen contact with the skin are our next steps.
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