Etale Anita, Onyianta Amaka J, Eloi Jean-Charles, Rowlandson Jemma, Eichhorn Stephen J
Bristol Composites Institute, School of Civil, Aerospace and Design Engineering, University of Bristol, Bristol, BS8 1TR, UK.
School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK.
Carbohydr Polym. 2024 Feb 1;325:121560. doi: 10.1016/j.carbpol.2023.121560. Epub 2023 Nov 10.
Urea and phosphoric acid are essential for the isolation of phosphorylated cellulose nanocrystals (CNCs). Besides limiting dissolution of nanocrystals, urea facilitates the swelling of fibres thus increasing access for the phosphorylating agent. The aim of this study was to determine optimal conditions for isolation of highly charged phosphorylated CNCs. Using a design of experiments approach, seventeen experiments in which reaction time, urea, and acid concentrations were varied, were conducted. A two-step process was used, in which CNCs were first isolated by treatment in phosphoric acid, and then treated with metaphosphoric acid, and urea. It is shown that a design of experiments approach to the phosphorylation of CNCs allows a much lower ratio of urea to acid than has previously been reported. CNCs with high surface charge (~1800 mmol kg) are possible using this method. This information is instructive to phosphorylation of cellulose nanomaterials which have a variety of applications e.g., water purification and medical biomaterials.
