Facile synthesis of self-dispersed β-cyclodextrin-coupled cellulose microgel for sustained release of vanillin

A self-dispersed β-cyclodextrin-coupled cellulose (β-CD-Cel) microgel was firstly synthesized via chemically coupling cellulose and β-CD in NaOH/urea aqueous solution. Following, after encapsulating the hydrophobic vanillin molecules into the cavities of β-CD-Cel microgel through host-guest interaction, cellulose-based long-lasting fragrance-released complex was obtained. β-CD was mainly bonded onto the hydroxyl groups at C₆ in the AGU units of cellulose, and about 0.5 β-CD molecule were introduced into the AGU unit when cellulose skeleton contained the β-CD content of 19.33%. FTIR, ¹H NMR, XRD, and UV-Vis provided evidences for the encapsulation of vanillin in the cavity of β-CD-Cel, and the encapsulating efficiency of vanillin for the β-CD-Cel inclusion complex was upped to 86.9%, which exceeded that of single β-CD small molecule encapsulating fragrance. Benefiting from the reversible host-guest interaction between β-CD and vanillin molecule, the continuous fragrance release time could exceed 196 h, and the sustained release behavior of β-CD-Cel complex could be adjusted by temperature. Also, the fragrance-released β-CD-Cel composite film showed high transparency, strong water resistance, and good flexibility. The vanillin retention of the composite film can keep 40% after soaking in ethanol solution for 96 h. This study will provide a new approach for the development of biomass functional coating.