Modulation of Morphology, Water Uptake/retention, and Rheological Properties by in- Situ Modification of Bacterial Cellulose With The Addition of Biopolymers

Abstract In situ modification of bacterial cellulose allows structural and morphological tuning which determines the crucial properties such as water absorption/retention and rheological behaviour. This work reports the effect of in situ modification carried out by adding of two biopolymers - Agar and Chitosan - to the standard culture media for bacterial cellulose synthesis. The agar modified BC (Agar-BC) frames the Bacterial cellulose (BC) network as reduced pore volume, and a much denser network, leading to lesser water absorption and further lower retention time than BC. Agar-BC also demonstrates a higher storage modulus, while the yield point is observed at a lower shear strain. This indicates densely packed behaviour of crosslinked polymer with low strain onset of plasticity. On the other hand, chitosan modified BC (Chitosan-BC) also exhibits a lower pore volume with lower densly packed structure and with lower swellability and water retention reduced to 1 hour (7 hours for BC). Chitosan-BC presents a lower modulus with a yield strain similar to that of unmodified BC. The water absorption-retention behaviour is discussed in details on the basis of relative pore shape-size distribution, fibre dimension and surface area. The mechanism of viscoelatic deformation for each of the cases is explained using a schematic illustrations of the presumed fiber morphologies.