High-Strength and Tough Cellulose Hydrogels Chemically Dual Cross-Linked by Using Low- and High-Molecular-Weight Cross-Linkers

Hydrogels are the focus of extensive research interests due to their potential application in the fields of biomedical materials, biosensors, agriculture, and cosmetics. Natural polysaccharide is one of the good candidates of these hydrogels. However, weak mechanical properties of cellulose hydrogels greatly limit their practical application. Here, chemically dual-cross-linked cellulose hydrogels (DCHs) were constructed by sequential reaction of cellulose with low- and high-molecular-weight cross-linkers to obtain relatively short chains and long chains cross-linked networks. Both the distribution and density of the cross-linking domains in the hydrogel networks were monitored by three-dimensional Raman microscopic imaging technique. Interestingly, the ruptured stress of DCHs in tensile and compressive tests were 1.7 and 9.4 MPa, which were 26.3- and 83.9-fold larger than those of chemically single-cross-linked cellulose hydrogel. The reinforcement mechanism of DCH was proposed, as the breaking of the short-chain cross-linking in the networks effectively dissipated mechanical energy, and the extensibility of the relatively long-chain cross-linking maintained the elasticity of DCH. Therefore, both the strength and toughness of DCH was enhanced, and the dual networks consisting of short-chain and long-chain cross-linking played an important role in the improvement of the mechanical properties of the cellulose hydrogels. The application prospect of the robust cellulose hydrogels with bimodal network structure would be greatly broadened in the sustainable biopolymer fields

High-Strength and Tough Cellulose Hydrogels Chemically Dual Cross-Linked by Using Low- and High-Molecular-Weight Cross-Linkers

Hydrogels are the focus of extensive research interests due to their potential application in the fields of biomedical materials, biosensors, agriculture, and cosmetics. Natural polysaccharide is one of the good candidates of these hydrogels. However, weak mechanical properties of cellulose hydrogels greatly limit their practical application. Here, chemically dual-cross-linked cellulose hydrogels (DCHs) were constructed by sequential reaction of cellulose with low- and high-molecular-weight cross-linkers to obtain relatively short chains and long chains cross-linked networks. Both the distribution and density of the cross-linking domains in the hydrogel networks were monitored by three-dimensional Raman microscopic imaging technique. Interestingly, the ruptured stress of DCHs in tensile and compressive tests were 1.7 and 9.4 MPa, which were 26.3- and 83.9-fold larger than those of chemically single-cross-linked cellulose hydrogel. The reinforcement mechanism of DCH was proposed, as the breaking of the short-chain cross-linking in the networks effectively dissipated mechanical energy, and the extensibility of the relatively long-chain cross-linking maintained the elasticity of DCH. Therefore, both the strength and toughness of DCH was enhanced, and the dual networks consisting of short-chain and long-chain cross-linking played an important role in the improvement of the mechanical properties of the cellulose hydrogels. The application prospect of the robust cellulose hydrogels with bimodal network structure would be greatly broadened in the sustainable biopolymer fields

Aesthetic Cellulose Filaments with Water-Triggered Switchable Internal Stress and Customizable Polarized Iridescence Toward Green Fashion Innovation

Healthy, convenient, and aesthetic hair dyeing and styling are essential to fashion trends and personal–social interactions. Herein, we fabricate green, scalable, and aesthetic regenerated cellulose filaments (ACFs) with customizable iridescent colors, outstanding mechanical properties, and water-triggered moldability for convenient and fashionable artificial hairdressing. The fabrication of ACFs involves cellulose dissolution, cross-linking, wet-spinning, and nanostructured orientation. Notably, the cross-linking strategy endows the ACFs with significantly weakened internal stress, confirmed by monitoring the offset of the C–O–C group in the cellulose molecular chain with Raman imaging, which ensures a tailorable orientation of the nanostructure during wet stretching and tunable iridescent polarization colors. Interestingly, ACFs can be tailored for three-dimensional shaping through a facile water-triggered adjustable internal stress: temporary shaping with low-level internal stress in the wet state and permanent shaping with high-level internal stress in the dry state. The health, convenience, and green aesthetic filaments show great potential in personal wearables

Ultrahigh Tough, Super Clear, and Highly Anisotropic Nanofiber-Structured Regenerated Cellulose Films

While tremendous efforts have been dedicated to developing environmentally friendly films made from natural polymers and renewable resources, in particular, multifunctional films featuring extraordinary mechanical properties, optical performance, and ordered nanostructure, challenges still remain in achieving all these characteristics in a single material via a scalable process. Here, we designed a green route to fabricating strong, super tough, regenerated cellulose films featuring tightly stacked and long-range aligned cellulose nanofibers self-assembled from cellulose solution in alkali/urea aqueous systems. The well-aligned nanofibers were generated by directionally controlling the aggregation of cellulose chains in the hydrogel state using a preorientation-assisted dual cross-linking approach; i.e., a physical cross-linking was rapidly introduced to permanently reserve the temporarily aligned nanostructure generated by preorienting the covalent cross-linked gels. After a structural densification in air-drying of hydrogel, high strength was achieved, and more importantly, a record-high toughness (41.1 MJ m–3) in anisotropic nanofibers-structured cellulose films (ACFs) was reached. Moreover, the densely packed and well-aligned cellulose nanofibers significantly decreased the interstices in the films to avoid light scattering, granting ACFs with high optical clarity (91%), low haze (<3%), and birefringence behaviors. This facile and high-efficiency strategy might be very scalable in fabricating high-strength, super tough, and clear cellulose films for emerging biodegradable next-generation packaging, flexible electronic, and optoelectronic applications

Table1_Mining of disease-resistance genes in Crocus sativus based on transcriptome sequencing.XLSX

Introduction:Crocus sativus L. has an important medicinal and economic value in traditional perennial Chinese medicine. However, due to its unique growth characteristics, during cultivation it is highly susceptible to disease. The absence of effective resistance genes restricts us to breed new resistant varieties of C. sativus.Methods: In present study, comprehensive transcriptome sequencing was introduced to explore the disease resistance of the candidate gene in healthy and corm rot-infected C. sativus.Results and discussion: Totally, 43.72 Gb of clean data was obtained from the assembly to generate 65,337 unigenes. By comparing the gene expression levels, 7,575 differentially expressed genes (DEGs) were primarily screened. A majority of the DEGs were completely in charge of defense and metabolism, and 152 of them were annotated as pathogen recognition genes (PRGs) based on the PGRdb dataset. The expression of some transcription factors including NAC, MYB, and WRKY members, changed significantly based on the dataset of transcriptome sequencing. Therefore, this study provides us some valuable information for exploring candidate genes involved in the disease resistance in C. sativus.</p

Construction of Transparent Cellulose-Based Nanocomposite Papers and Potential Application in Flexible Solar Cells

Flexible electronics are developing rapidly due to promising applications in displays, sensors, and energy conversion fields. For biodegradable, lightweight, and flexible thin film electronics to be explored, <i>O</i>-(2,3-Dihydroxypropyl) cellulose (DHPC) was synthesized by homogeneous etherification of cellulose in 7 wt % NaOH/12 wt % urea aqueous solution without extra catalyst. DHPC exhibited a high level of transparency, outstanding ductility, and good adhesiveness but poor mechanical properties. Thus, stiff tunicate cellulose nanocrystals (TCNCs) were introduced to construct tough nanocomposite papers. The reinforcement of nanocomposite papers was well predicted by a percolating model, indicating the formation of the network of TCNCs. On the basis of the excellent interfacial compatibility between TCNCs and DHPC, supported by atomic force microscope mapping, the nanocomposite papers exhibited smooth surface, high transparency, as well as satisfactory mechanical properties, which were suitable for the construction of flexible polymer solar cells. Tin-doped indium oxide could be directly coated on the adhesive transparent paper without any glue as electrode, and the power conversion efficiency of the resulting flexible inverted polymer solar cells was 4.98%, suggesting its potential application as biodegradable and wearable electronics or optoelectronics. This work is important for developing clean energy by using sustainable materials derived from renewable resources

Table2_Mining of disease-resistance genes in Crocus sativus based on transcriptome sequencing.DOCX

Introduction:Crocus sativus L. has an important medicinal and economic value in traditional perennial Chinese medicine. However, due to its unique growth characteristics, during cultivation it is highly susceptible to disease. The absence of effective resistance genes restricts us to breed new resistant varieties of C. sativus.Methods: In present study, comprehensive transcriptome sequencing was introduced to explore the disease resistance of the candidate gene in healthy and corm rot-infected C. sativus.Results and discussion: Totally, 43.72 Gb of clean data was obtained from the assembly to generate 65,337 unigenes. By comparing the gene expression levels, 7,575 differentially expressed genes (DEGs) were primarily screened. A majority of the DEGs were completely in charge of defense and metabolism, and 152 of them were annotated as pathogen recognition genes (PRGs) based on the PGRdb dataset. The expression of some transcription factors including NAC, MYB, and WRKY members, changed significantly based on the dataset of transcriptome sequencing. Therefore, this study provides us some valuable information for exploring candidate genes involved in the disease resistance in C. sativus.</p