Abstract
Most cellulose-based materials’ manufacturing processes include processing this biopolymer in an aqueous medium. Sorption properties depend on cellulose supramolecular structure and nature of its change during moistening. Plenty of researchers’ efforts have been directed to the development of scientifically sound and commercially reliable processes over the past decade for the cellulose fibers’ dispersion in an aqueous medium. Therefore, it needs a more detailed study of the cellulose–water system components’ interaction. This study presents the supramolecular structure and sorption properties of native cotton cellulose research results obtained by 1H NMR relaxation, spectroscopy and sorption measurements. Hydrophilic properties of cellulose as an adsorbent are characterized, taking into account a porous system between its structural elements. We examine in detail water adsorption on the active surface of cellulose Iβ. We also demonstrate the approach for determining the entropy change in the first two layers of adsorbed water and estimate this value increased during adsorption. Cellulose moistening is accompanied by the decomposition of macrofibrils into microfibrils and is manifested in a crystallinity decrease and a specific surface area growth.
Highlights
Cellulose is one of the most common natural polymers with such essential properties as renewability and biodegradation (Li and Renneckar 2011; Grunin et al 2012, 2015a; French 2017; Lindh et al 2017)
Cellulose macrofibril is formed by four partially co-crystallized MFs, each of which consists of four elementary fibril (EF), interconnected by relatively weak donor–acceptor hydrogen bonds
The model of the cellulose supramolecular structure is presented. It takes into account the crystallinity of cellulose and the presence of slit-shaped pores located between its structural elements
Summary
Cellulose is one of the most common natural polymers with such essential properties as renewability and biodegradation (Li and Renneckar 2011; Grunin et al 2012, 2015a; French 2017; Lindh et al 2017). During the passage of glucose units through terminal complexes of the plasma membrane, chemical 1,4-β-glycosidic bonds form cellulose chains (Delmer and Amor 1995; Doblin et al 2002; Brown 2004; Nishiyama et al 2008; Nishiyama 2009; Grunin et al 2012, 2015b). These cellulose chains aggregate into the elementary fibril (EF) by hydrogen bonds. Each glucopyranose ring of cellulose chain inside of cellulose crystallites undergoes intra-, intermolecular and interlayer donor–acceptor hydrogen bonds This increases the aggregation strength of cellulose chains and leads to the impossibility of penetration of water molecules into the depth of cellulose EFs (Nishiyama et al 2002, 2003; Li and Renneckar 2011)
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