From Fibrillar Networks to Functional Materials: Structure, Properties and Applications of Nanocellulose Networks

In this thesis, we focussed on unravelling the unique attributes of cellulose microfibril (CMF) networks using different experimental tools, in order to further the application potential of these sustainable material systems. As a first step, we quantified the 3D micro and nano-scale structure of CMF networks in situ using confocal microscopy and image analysis methods. The inter-fibrillar interactions between CMFs were quantified theoretically and experimental implementation of these findings resulted in significant changes in their network microstructure. From a rheological perspective, we showed that these networks undergo a transition with increasing shear stress from a predominantly elastic to a plastic deformation and are capable of quickly regaining their original viscoelastic moduli upon removal of the stress. We also studied the properties of a composite system obtained on combining CMFs with another commonly used bio-based polymer, agarose. The composite networks exhibited a synergistic enhancement in the stiffness depending on the ratio of its constituent networks. Finally, we provided a template for the fabrication of CMFs- based transparent functional films, which are potential alternatives for petroleum-based plastics in many applications.