Cellulose Solubility: Dissolution and Analysis of "Problematic" Cellulose Pulps in the Solvent System DMAc/LiCl

High-Value Utilization of Cellulose: Intriguing and Important Effects of Hydrogen Bonding Interactions─A Mini-Review

Cellulose has been widely used in papermaking, textile, and chemical industries due to its diverse sources, environmental friendliness, and renewability. Recently, much more attention has been paid to converting cellulose into high-value-added products. Therefore, the extraction of nanocellulose, the dissolution of cellulose, and their applications are some of the most important research topics currently. However, cellulose's dense hydrogen bond network poses challenges for efficient extraction and dissolution, limiting its potential for functional material development. This review discusses the mechanisms of hydrogen bond disruption and weak interactions during nanocellulose extraction and cellulose dissolution. Key challenges and future research directions are highlighted, emphasizing developing efficient, ecofriendly, and cost-effective methods. Additionally, this review provides theoretical insights for constructing high-performance cellulose-based materials.

A fresh perspective on dissociation mechanism of cellulose in DMAc/LiCl system based on Li bond theory

In this case, various characterization technologies have been employed to probe dissociation mechanism of cellulose in N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) system. These results indicate that coordination of DMAc ligands to the Li+-Cl- ion pair results in the formation of a series of Lix(DMAc)yClz (x = 1, 2; y = 1, 2, 3, 4; z = 1, 2) complexes. Analysis of interaction between DMAc ligand and Li center indicate that Li bond plays a major role for the formation of these Lix(DMAc)yClz complexes. And the saturation and directionality of Li bond in these Lix(DMAc)yClz complexes are found to be a tetrahedral structure. The hydrogen bonds between two cellulose chains could be broken at the nonreduced end of cellulose molecule via combined effects of basicity of Cl- ion and steric hindrance of [Li (DMAc)4]+ unit. The unique feature of Li bond in Lix(DMAc)yClz complexes is a key factor in determination of the dissociation mechanism.

On the Mechanism of the Ionizing Radiation-Induced Degradation and Recycling of Cellulose

The use of ionizing radiation offers a boundless range of applications for polymer scientists, from inducing crosslinking and/or degradation to grafting a wide variety of monomers onto polymeric chains. This review in particular aims to introduce the field of ionizing radiation as it relates to the degradation and recycling of cellulose and its derivatives. The review discusses the main mechanisms of the radiolytic sessions of the cellulose molecules in the presence and absence of water. During the radiolysis of cellulose, in the absence of water, the primary and secondary electrons from the electron beam, and the photoelectric, Compton effect electrons from gamma radiolysis attack the glycosidic bonds (C-O-C) on the backbone of the cellulose chains. This radiation-induced session results in the formation of alkoxyl radicals and C-centered radicals. In the presence of water, the radiolytically produced hydroxyl radicals (●OH) will abstract hydrogen atoms, leading to the formation of C-centered radicals, which undergo various reactions leading to the backbone session of the cellulose. Based on the structures of the radiolytically produced free radicals in presence and absence of water, covalent grafting of vinyl monomers on the cellulose backbone is inconceivable.

Cellulose Cryogels as Promising Materials for Biomedical Applications

The availability, biocompatibility, non-toxicity, and ease of chemical modification make cellulose a promising natural polymer for the production of biomedical materials. Cryogelation is a relatively new and straightforward technique for producing porous light and super-macroporous cellulose materials. The production stages include dissolution of cellulose in an appropriate solvent, regeneration (coagulation) from the solution, removal of the excessive solvent, and then freezing. Subsequent freeze-drying preserves the micro- and nanostructures of the material formed during the regeneration and freezing steps. Various factors can affect the structure and properties of cellulose cryogels, including the cellulose origin, the dissolution parameters, the solvent type, and the temperature and rate of freezing, as well as the inclusion of different fillers. Adjustment of these parameters can change the morphology and properties of cellulose cryogels to impart the desired characteristics. This review discusses the structure of cellulose and its properties as a biomaterial, the strategies for cellulose dissolution, and the factors affecting the structure and properties of the formed cryogels. We focus on the advantages of the freeze-drying process, highlighting recent studies on the production and application of cellulose cryogels in biomedicine and the main cryogel quality characteristics. Finally, conclusions and prospects are presented regarding the application of cellulose cryogels in wound healing, in the regeneration of various tissues (e.g., damaged cartilage, bone tissue, and nerves), and in controlled-release drug delivery.

Newer guar gum ester/chicken feather keratin interact films for tissue engineering

This work intends to synthesis newer guar gum indole acetate ester and design film scaffolds based on protein-polysaccharide interactions for tissue engineering applications. Guar gum indole acetate(GGIA) was synthesized for the first time from guar gum in presence of aprotic solvent activated hofmeister ions. The newer biopolymer was fully characterized in FT-IR,¹³C NMR, XRD and TGA analysis. High DS (Degree of Substitution, DS = 0.61) GGIA was cross-linked with hydrolyzed keratin, extracted from chicken feather wastes. Films were synthesized from different biopolymer ratios and the surface chemistry appeared interesting. Physicochemical properties for GGIA-keratin association were notable. Fully bio-based films were non-cytotoxic and exhibited excellent biocompatibility for human dermal fibroblast cell cultivations. The film scaffold showed 63% porosity and the recorded tensile strength at break was 6.4 MPa. Furthermore, the standardised film exerted superior antimicrobial activity against both the Gram-positive and Gram-negative bacteria. MICs were recorded at 130 μg/mL and 212 μg/mL for E. coli and S. aureus respectively. In summary, GGIA-keratin film scaffolds represented promising platforms for skin tissue engineering applications.