Chemical hydrophobic modification of inulin in aqueous media: Synthesis of β-hydroxyalkyl ethers of inulin

Neutral hydrophobic β-hydroxyalkyl ethers of inulin have been prepared with varying molecular features (the hydrophobic characteristics of the epoxide, length and nature, and the number of grafted groups per fructose units) in aqueous media under different conditions. The influence of several reaction parameters such as amount of solubilizer (isopropyl alcohol), basic catalysts, reaction time and temperature on the reaction efficiency has been studied through NMR analysis. We can state that the etherification of inulin in water is limited by the hydrophobic effect due to the alkyl chain of the epoxide, which can be avoided by adjusting the required amount of a solubilizer. On the other hand, the etherification rate appears to be strongly related to the temperature. Pure short and medium chain length β-hydroxyalkyl ethers of inulin can be obtained in KOH water media at 80 °C using 40% (w/w) of inulin concentration with reasonably good efficiencies and reaction times.