Impact of calcium-carboxylate interactions in cellulose nanofiber reinforced alginate based film with triple-decker-like structure

Abstract Biofilm with compact structure was assembled through layer-by-layer casting technology. Herein, triple-decker-like films were prepared using alginate (ALG) and TEMPO-oxidized nanocellulose (TOCN), followed by the comparisons of film properties before and after Ca2+ crosslinking. Addition of TOCN as a reinforcement increased the mechanical properties of ALG film significantly, e.g. addition of 7.5 % of TOCN increased the tensile strength (TS) of the film from 92.22 to 112.12 MPa. After Ca2+ treatment, the properties of the crosslinked film were further enhanced where the TS increased to 126.23 MPa compared with the pristine film (99.13 MPa). Besides, Ca2+ treated film revealed a higher thermal stability than the non-crosslinked ones. Scanning electron microscopy and energy dispersive spectrum, and flourier transform infrared spectroscopy showed the uniform distribution of Ca2+, and the enhanced hydrogen and ionic interactions. This phenomenon further revealed that the carboxylic groups on the surface of TOCN might participate in the construction of structure of ALG-based film. The increased insolubility and mechanical strength as well as the reduced water vapor permeability of the crosslinked films could remarkably extend the use of polysaccharide in various applications, especially food packaging.