Sustainable Transesterification of Cellulose with High Oleic Sunflower Oil in a DBU-CO2 Switchable Solvent

The direct transesterification of cellulose with high oleic sunflower oil, without any activating steps, was achieved in a DBU-CO2 solvent system to obtain fatty acid cellulose esters (FACEs). Optimization of the reaction parameters (i.e., concentration, temperature, plant oil equivalents, as well as reaction time) was performed using microcrystalline cellulose (MCC) and followed by Fourier-transform infrared spectroscopy (FT-IR). Further confirmation of the FACEs structures was achieved via 1H and 13C NMR, and 31P NMR revealed DS (degree of substitution) values of up to 1.59. The optimized conditions were successfully applied to filter paper (FP) and cellulose pulp (CP). Characterization of the FACEs showed improved thermal stability after transesterification reactions (up to 30 °C by TGA) and a single broad 2θ peak around 19.8° by XRD, which is characteristic of a more amorphous material. In addition, films were prepared via solvent casting and their mechanical properties obtained from tensile strength ...