Physicochemical properties of new silicone alternatives unraveled by experimental and molecular modeling techniques

Abstract

The cosmetic industry has recognized an increasing demand for environmentally sustainable solutions due to the classification of certain commonly used components as bioaccumulative and hazardous. The European Union has implemented restrictions on the utilization of some components, including silicones, which limit their concentration. The present investigation intends to find new solutions for cosmetic formulations by combining molecular dynamics simulations with an array of experimental techniques to fully characterize silicone alternatives. The novelty of the work relies on the addition of an organic deep eutectic solvent and ester-based emollients in place of conventional silicones. These formulations exhibit great stability when adding a 15% weight-to-weight glycerol:lactic acid eutectic mixture, acting as both a solvent and a thickener-like behavior. The novel esters were incorporated into a cosmetic-based formulation and tested to comprehend their physicochemical properties, stability, and molecular distribution. Widely used silicones and commercial silicone alternatives were also tested for comparison purposes. Based on our research findings, it has been determined that the new emollients, specifically decyl heptanoate, decyl octanoate, and decyl decanoate, conferred great stability and performance to the tested formulations. The formulations comprising the novel esters exhibit superior spreadability compared to those including silicones and are comparable to formulations using commercially available alternatives. The modeling techniques applied disclose the molecular features behind the component’s distribution, helping to differentiate the formulations where the key molecule─silicon or alternative─has induced phase separation or not. This creates the opportunity to optimize the entire production process by foreseeing the function of new esters in a formulation.