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

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.