Oleochemical carbonates: A comprehensive characterization of an emerging class of organic compounds

Dialkyl carbonates (DAC) with short-medium alkyl length - oleochemical carbonates - are attracting attention because of their appealing properties, including low viscosity, flammability, toxicity, environmental impact and wide range of applications: lubricants, personal care, fuel additives etc. However, not much is known concerning their chemical physical properties and, more importantly, on the nature of microscopic correlations that eventually determine bulk performances. In view of this paucity, we present a large exploration of a series of chemical physical properties of a set of DACs ranging from dimethyl up to didodecyl carbonate. This study extends previously determined databases, thus providing a complete picture of the temperature dependence of chemical physical properties around room temperature. Furthermore, we explored the microscopic morphology of DACs, by synergic exploitation of X-ray scattering and Molecular Dynamics techniques. These tools allow detecting the existence of a distinct degree of mesoscopic spatial segregation between polar carbonate moieties and apolar alkyl chains domains. The role of first neighbour carbonate moieties in driving the corresponding molecules towards weak hydrogen bonding interactions and alkyl chain alignment is described. Such an effect is related to the overall mesoscopic segregation of alkyl tails that isolate small droplets formed by stacked carbonate groups. Such a highly compartmentalised morphology can explain and potentially suggest applications of DACs in fields as relevant as separation, catalysis, lubrication etc.