Efficient Synthesis, Calorimetric and Rheological Studies of Symmetrical Biobased Fatty Ethers

Four linear biobased fatty ethers (di-n-dodecyl, di-n-tetradecyl, di-n-hexadecyl, and di-n-octadecyl ethers) have been synthesized from free fatty alcohols according to a green and simple efficient method. Their melting temperatures, Tₘ, were studied by using the differential scanning calorimetry (DSC) technique. Ethers showed higher Tₘ (28–62 °C) than their corresponding alcohols, but the temperature difference between one ether and its alcohol rapidly decreases as the carbon number in the molecules increases. Melting enthalpy, ΔHₘ, of an ether was approximately twice the ΔHₘ of its corresponding alkanol. Flow properties were also studied between Tₘ and 100 °C. Ethers behaved as Newtonian liquids with viscosities from 1.8 to 20 mPa·s. Below 80 and 65 °C, respectively, di-n-dodecyl and di-n-tetradecyl ethers showed lower viscosity than their corresponding alcohol. The temperature–viscosity curves were fitted with an Arrhenius-type relationship. Flow activation energies were significantly lower for the ethers than for the alcohols: around 20 and 28 kJ/mol, respectively.