Nanostructures in clear and homogeneous mixtures of rapeseed oil and ethanol in the presence of green additives

Abstract

Ethanol and rapeseed oil are mixed in the presence of tributyl citrate, 2,5-dimethylfuran, 2-methylfuran, 2-methyl tetrahydrofuran, methyl tert butyl ether, ethyl tert butyl ether, FAME-rapeseed biodiesel, 1-heptanol, and 2-ethylhexyl nitrate, at 25 °C (298.15 K). All these additives come or can be obtained completely or partially from plants. The obtained ternary phase diagrams show a large domain of clear and homogeneous solutions and a liquid two-phase system due to the partial solubility of rapeseed oil and ethanol. All the tested additives have thus an evident cosolvent behavior for ethanol and rapeseed oil. In all the studied systems, the possible presence of nanostructures is checked with dynamic light scattering (DLS) and confirmed using static light scattering (SLS). In the system rapeseed oil/ethanol/1-heptanol, the presence of nanostructures is definitely established performing small-angle neutron scattering (SANS). The true geometry of these nanostructures could not be detected, but systematic conductivity measurements starting with the binary melt 1-heptanol/rapeseed oil in the presence of LiClO4 adding ethanol show clearly a continuous transition from ethanol-in-rapeseed oil to rapeseed oil-in-ethanol mixtures passing through a bicontinuous medium.