In this study, a cardanol-bonded chitin was synthesized for the first time via acylation of chitin dissolved in an ionic liquid, 1-allyl-3-methylimidazolium bromide, with an activated cardanol, prepared from 3-pentadecylphenoxy acetic acid and 1,1′-carbonyldiimidazole. Although the introduction of cardanol substituents induced no crystallization of the chitin chains and the appearance of a glass transition temperature (Tg), the resulting derivative did not exhibit useful properties, such as thermoplasticity for melt-press processing, due to strong interaction among the cardanol substituents. Therefore, the remaining hydroxy groups were further acylated using several fatty acyl chlorides in a LiCl/DMAc solvent to afford a series of cardanol-bonded mixed chitin esters entirely composed of naturally occurring moieties. The chemical structures and degrees of substitution (DSs) of the products were characterized by IR and 1H NMR spectroscopies. The obtained cardanol-bonded mixed chitin esters exhibited thermoplastic behavior owing to the reduced interaction among the cardanol substituents, accompanied by the appearance of Tgs, which enabled the film formation by melt-pressing at 150 °C at 15 MPa. The thermal properties of the derivatives, evaluated by differential scanning calorimetric analysis, were systematically discussed in accordance with structures and DSs of the substituents.
Totani et al. (Thu,) studied this question.