Functional trends and rheological evaluation of polyurethane microcapsules in dermato-cosmetic applications

Abstract To date, natural and synthetic polymer-based microcapsules have been used extensively in various dermato-cosmetic applications, with an emphasis on the targeted delivery of active ingredients, including therapeutic and aesthetic interventions. Although numerous polymer candidates have been comprehensively investigated, polyurethane based microcapsules have received comparatively minor attention, despite possessing a multitude of intrinsic benefits. However, in recent years, although there has been an upsurge of studies involving polyurethane, predominantly as a capsule wall or shell component, towards tangible dermato-cosmetic applications, these are only intermittently documented. In the current review, we target this lacuna, explore, and collate only the most contemporary trends and advances (2017-to date) in the field. In addition, despite the significance, and pertaining to the acute deficiency of rheological studies targeting polyurethane-based microcapsules in dermato-cosmetic applications, we critically examine and lay a comprehensive interpretation, based on the current state-of-the-art, inevitability for systematic inquiries, and identification of several target domains that need urgent attention. Finally, we deliberate on the challenges and the impending projections from a diverse outlook. We focus on a steady and more sustainable path forward via incorporation of green raw materials, cumulative domain-optimized and customer-focused applications, and a significantly improved understanding of the microcapsule mechanical behavior via implementation of novel rheological characterization procedures.