Abstract
In situ modification of bacterial cellulose (BC) 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 two biopolymers Agar and Chitosan to the standard culture media for bacterial cellulose synthesis. The agar modified BC (Agar-BC) form a BC network with 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 a behaviour similar to that of a crosslinked polymer with a low strain onset of plasticity. On the other hand, chitosan-modified BC (Chitosan-BC) also exhibits a lower pore volume with a lower densely packed structure and with lower swellability and water retention reduced to 1 h (7 h 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 detail considering the relative pore shape-size distribution, fibre dimension and surface area. The mechanism of viscoelastic deformation for each of the cases is explained.
Highlights
Cellulose is abundant in nature owing to its various sources such as plants, trees, microbes, and algae, which can be processed chemically and enzymatically to obtain cellulose (Lynd et al 2002)
This paper looks into the changes in structure, morphology, water absorption, and retention of Bacterial cellulose (BC) produced by in situ modification with 0.1% Agar and chitosan, with emphasis on understanding the rheological characteristics
The common peaks corresponding to cellulose are observed in the spectra corresponsing to BC - a broad characteristic peak at 3353 cm−1 for -OH stretching vibration, a peak at 2900 cm−1 attributed to aliphatic C-H stretching vibration, and a peak at 1436 cm−1 ascribed for C-H bending vibrations (Numata et al 2019; Ullah et al 2016b)
Summary
Cellulose is abundant in nature owing to its various sources such as plants, trees, microbes, and algae, which can be processed chemically and enzymatically to obtain cellulose (Lynd et al 2002). Intensive and extensive chemical processing is needed to extract pure cellulose for its various applications (Shoda and Sugano 2005; Szymańska-Chargot et al 2017b). BC possesses good mechanical properties and high water-absorbing and holding capacity (Islam et al 2017). Due to its high purity, mechanical strength, crystalline nature, liquid-absorbing, and holding capabilities, biodegradability and most importantly its biocompatibility, BC is of particular interest in drug delivery, bioactive implants, artificial blood vessels, cosmetology and tissue scaffolds (Ullah et al 2016a)
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