Novel cellulose-gelatin composite films made from self-dispersed microgels: Structure and properties

A series of epichlorohydrin-couple-linked cellulose-gelatin composite films (ECGF) was fabricated in NaOH/urea aqueous solution using a process involving homogenous blending, coupling, dialysis, self-dispersion, microgel solution casting, and evaporation. Their structure and properties were characterized with elemental analysis, Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC), scanning electron microscope (SEM), atomic force microscopy (AFM), ultraviolet-visible (UV-vis) spectroscopy, water vapor permeability, and mechanical testing. The results showed that the self-dispersed cellulose-gelatin microgels were successfully prepared and the coupling interactions existed in the inter- and intra-molecules of the corresponding composite films during the fabrication process. The water vapor permeability of the ECGF films was improved when the protein content was higher than 30 wt% in composite films at 75% relative humidity. Interestingly, compared with the cellulose/protein composite films prepared via phase separation method, ECGF films exhibited more homogeneous surface and compact cross-section structures, as well as presented higher light transmittance at 400 nm of about 88% and relative lower swelling ratio. Moreover, ECGF films displayed higher tensile strength compared with that of water-soluble cellulose derivatives/protein composite films in dry and wet states.