Modifying bacterial cellulose dispersions with deep eutectic solvent and pectin to tune the properties of open-celled foams†

Abstract

The overconsumption of plastics has led to a significant micro/nanoplastics pollution problem, driving an urgent need for sustainable alternatives. Synthetic polymer foams such as expanded polystyrene (EPS), polyethylene (PE), and polyurethane (PU), contribute significantly to plastic waste, often ending up in landfills after short service lives. In this article, we present a comprehensive investigation of bacterial cellulose (BC)/pectin composite foams, focusing on how modifications to the biopolymer network and macromolecular interactions influence colloidal and solid-state properties. By treating BC with a citric acid-based deep eutectic solvent (DES), we enhance its colloidal stability, achieving a zeta potential 81.2% more negative, and improve the compressive strength of the resulting foams by 23.8%. Introducing pectin further transforms the structure of the BC network, and significantly alters its electrostatic and rheological properties. The zeta potential reaches absolute values as high as 30.3 mV at 80% pectin, while the recoverability increases and the storage and loss moduli decrease with increasing pectin concentration. Small-angle X-ray scattering (SAXS) reveals modifications in the network structure that provide insight into the substantial changes in the morphological and mechanical properties of the foams. The resulting binary biopolymer foams demonstrate strength and stiffness rivaling those of synthetic polymer foams of similar density. Overall, we demonstrate the critical role of colloidal interactions in tuning the mechanical properties of binary biopolymer solid foams, and highlight the potential of this sustainable and biodegradable system to address pressing environmental issues caused by plastic waste.