Cellulose

Morphology and supramolecular structure characterization of cellulose isolated from heat-treated moso bamboo Abstract The change of physical and mechanical properties of bamboo after heat treatment has become a research hotspot recently. However, bamboo was usually used as a whole to investigate the reason why its properties changed. This study focused on cellulose, the skeleton substance of bamboo cell wall. Changes in morphology and supramolecular structure of cellulose isolated from heat-treated moso bamboo were investigated. The results showed bamboo cellulose after heat treatment was more prone to structure changes when treated with alkali solution. Taking the cellulose sample isolated from 200 °C heat-treated bamboo as an example, its X-ray crystallinity index of cellulose increased from 70.5% for the untreated sample to 75.6% for the sample heated to 200 °C including both cellulose I and II peaks. Based on CP/MAS 13C NMR measurements, the cellulose Iα/cellulose Iβ ratio decreased from 28 to 22% and the cellulose I/cellulose II ratio decreased from 162 to 49%. These changes in supramolecular structure caused the morphology to suffer tremendous changes, where the cellulose in fibers became shorter, thinner and twisted and the cellulose in parenchyma cells shrunk.

Triazine mediated covalent antibiotic grafting on cotton fabrics as a modular approach for developing antimicrobial barriers Abstract New antimicrobial textiles were prepared through direct chemical linkage of bioactive molecules eugenol and fluoroquinolone derivatives, onto the surface of cotton fabrics. The attachment through a triazine moiety minimizes the leaching of the antimicrobial molecule into the surroundings of the material. Bacterial efficacy against Staphylococcus aureus and Pseudomonas aeruginosa was studied. The treated textile with fluoroquinolone demonstrated bacteriostatic antimicrobial effects having a tendency to decrease the population of S. aureus in the planktonic form. A significant effect was also observed in the prevention of S. aureus biofilm formation and in its ability to kill bacteria within a preformed biofilm. Eugenol-modified fabric was also active in the process of eradicating preformed P. aeruginosa biofilms. Further, in vitro assays using human dermal fibroblast cells indicate no effects on cell proliferation and viability, and in vivo tests in a murine skin wound model showed no increase of IL-6 for full-thickness wounds that were in contact with the fabrics. Graphic abstract

Development of hydrogels based on oxidized cellulose sulfates and carboxymethyl chitosan Abstract Cellulose or chitosan represent highly abundant biopolymers possessing excellent biocompatibility that is required in tissue engineering. Both, cellulose and chitosan can be used to form hydrogels that can replace soft human tissues like cartilage. Hence, we developed here an approach to oxidize cellulose after sulfation, which was then crosslinked with carboxymethyl chitosan (CMCh). Sulfation was performed either by direct or acetosulfation reaching different sulfation degrees of DSSulf = 0.8–2.0. Subsequently oxidation of cellulose sulfate (CS) was performed with sodium periodate, which yielded aldehyde contents of DSAld = 0.1–0.3. Since oxidation requires the presence of vicinal hydroxyl groups in the anhydroglucose unit (AGU) of CS, higher sulfation degree as obtained by direct sulfation including hydroxyl groups at C2 and C3-position yielded lower aldehyde contents. On the contrary, regioselective sulfation at C6-position by acetosulfation was more suitable to achieve higher oxidation degrees of CS. Consequently, hydrogel formation obtained by chemical crosslinking of oxidized cellulose sulfate (oCS) with CMCh was fast within seconds when oxidation degree was high, but sulfation degree low. Moreover gel formation lasted almost 24 h when sulfation degree was high. It could also be shown that hydrogels based on oCS with a DSAld  of 0.28 or higher were stable for 25 days when incubated in phosphate-buffered saline (PBS) or Dulbeccos modified Eagle medium (DMEM). Studies with pH dependent fluorescent tracer molecules could show that the intrinsic pH value in hydrogels was slightly acidic ( \(\sim\) pH 6.4) when they were incubated in PBS at pH 7.4. Mass transfer and homogeneity of the gel network was studied by NMR finding that diffusion of water molecules was not hindered inside the hydrogels.

Synthesis of P–N–Si synergistic flame retardant based on a cyclodiphosphazane derivative for use on cotton fabric Abstract A durable and effective flame retardant (FR) was synthesized in this work by taking advantage of the high reactivity of a cyclodiphosphazane derivative, without the use of formaldehyde. The FR is halogen-free and has the synergistic effect of phosphorus, nitrogen and silicon. Fire resistance of the cotton fabrics is significantly enhanced after the FR treatment. The limiting oxygen indices of cotton treated with 30% FR increase from 18.2 to 52.9% and decrease to 27.2% after 50 launder cycles, demonstrating that the proposed material is a durable FR. The thermo-gravimetric analysis results indicate that compared with the control cotton, the degradation process of the treated cotton occurred at a lower temperature range, the degree of degradation was lower, and the residue is improved. The total heat release and the effective heat combustion values are notably lower for the treated cotton than the control cotton. Furthermore, mechanical property tests demonstrate that the tensile strength is largely retained, while the bending length of the treated cotton partly increases. The surface morphology of the treated cotton is investigated with scanning electron microscopy. Fourier transform infrared and elemental analysis show that the FR was successfully grafted onto the surface of the cotton fabric. 1H, 13C, and 31P nuclear magnetic resonance verify the chemical structure of the FR. Graphic abstract

Preparation and evaluation of oxygen scavenging nanocomposite films incorporating cellulose nanocrystals and Pd nanoparticles in poly(ethylene-co-vinyl alcohol) Abstract There is current interest in active packaging, where the packaging material exhibits desirable functions in addition to containment of product. One of these functions is to reduce the oxygen content in the package in order to minimize product oxidation and spoilage, and prolong product shelf-life. In this work, we have developed novel nanocomposites, comprising cellulose nanocrystals and Pd nanoparticles embedded in an ethylene–vinyl alcohol copolymer (EVOH). The nanocellulose is a critical component in the nanocomposite because it acts not only as reducing agent for PdCl2 but also as support for the dispersion of Pd nanoparticles on EVOH film and enhances the physical properties of the EVOH. Pd nanoparticles react with oxygen to serve as oxygen scavenger. The cellulose nanocrystals have also been optionally oxidized, and the increased presence of carboxyl groups favored a better distribution of the Pd nanoparticles, thereby enabling improved oxygen absorption. These features make the nanocomposites promising candidates as active packaging materials. Included in this work are the preparation and the characterization of these materials.

Influence of torrefaction pretreatment on the pyrolysis characteristics of seaweed biomass Abstract Torrefaction is a promising pretreatment technology for biomass and its pyrolysis products upgrading. The aim of this study was to investigate the effect of torrefaction on the pyrolysis of seaweed biomass. TG, Py-GC/MS and fixed-bed experiments were used at a series of typical torrefaction temperatures (225 °C, 250 °C, 275 °C and 300 °C) and pyrolysis temperatures (450 °C, 500 °C, and 550 °C). The results showed that increasing of torrefaction temperature led to gradual reduction in moisture content and volatile content due to the precipitation of water and volatile functional groups (OH, NH, CO, C=O, etc.), which resulted in increase of solid products of torrefied seaweed. In addition, the liquid yield showed a promotion at first and then decreased. It also indicated that thermal stability of seaweed became stronger after the pretreatment leading to the initial pyrolysis temperature shifting toward the high temperature section. Meanwhile, the maximum pyrolysis weight loss rate and the total weight loss got a reduction. Moreover, the optimal conditions for maximum bio-oil production were obtained when the temperature of torrefaction was 250 °C at the pyrolysis temperature of 500 °C. Furthermore, the bio-oil under such conditions gave the highest relative content of aromatic hydrocarbons.

Correction to: Modification of hyperbranched hemicellulose polymer and its application in adsorbing acid dyes In the original publication of the article, the graphical abstract and Scheme 1(a) and Scheme 1(b) were published incorrectly.

Cellulose carbamate derived cellulose thin films: preparation, characterization and blending with cellulose xanthate Abstract Cellulose carbamate (CC) was employed as a water-soluble precursor in the manufacturing of cellulose based thin films using the spin coating technique. An intriguing observation was that during spin coating of CC from alkaline aqueous solutions, regeneration to cellulose was accomplished without the addition of any further chemicals. After rinsing, homogeneous thin films with tunable layer thickness in a range between 20 and 80 nm were obtained. Further, CC was blended with cellulose xanthate in different ratios (3:1, 1:1, 1:3) and after regeneration the properties of the resulting all-cellulose blend thin films were investigated. We could observe some slight indications of phase separation by means of atomic force microscopy. The layer thickness of the blend thin films was nearly independent of the ratio of the components, with values between 50 and 60 nm for the chosen conditions. The water uptake capability (80–90% relative to the film mass) determined by H2O/D2O exchange in a quartz crystal microbalance was independent of the blend ratio.

Analytical ultracentrifugation and other techniques in studying highly disperse nano-crystalline cellulose hybrids Abstract The development of functional nano-crystalline cellulose hybrid suspensions has been in the focus of many areas of industry and academia for the past decades. The attention is elucidated from a unique biocompatible, mechanical, solution etc. properties of cellulose based systems. Fabrication of functional cellulose hybrids with customized features requires detailed knowledge of their final properties as well as understanding the structure–property relationships between the initial ingredients. The reported study investigates the formation and corresponding fundamental solution and molecular characteristics of highly disperse nano-crystalline cellulose hybrids with aluminum oxide nanoparticles. The characterization of the final complexes and its primary components was performed mainly in solution, using basic complementary hydrodynamic approaches, substantially—sedimentation velocity analysis in the analytical ultracentrifuge and related techniques. The analysis of the solution behavior resolved information about the hydrodynamic size, molar mass, shape, asymmetry and composition of the complexes. Additionally morphology of the cellulose hybrids was investigated by scanning force microscopy. To this end we demonstrate complete structural examination of highly disperse colloidal suspensions of crystal nano-cellulose modified by aluminum nanoparticles using classical solution characterization techniques. Graphic abstract

A comprehensive kinetic simulation of different types of plant fibers: autocatalytic degradation mechanism Abstract Kinetic analysis of the non-isothermal degradation of three different plant fibers has been performed using isoconversional model-free methods, model-fitting methods in order to establish if different kinetic approaches provide consistent kinetic parameters. It has been shown that these approaches provide consistent kinetic parameters and can be combined in such a way as to enhance the reliability and quality of each other and consequently the overall kinetic analysis. As a result, the most probable kinetic parameters for the non-isothermal degradation of three different types of plant fibers determined were autocatalytic-type mechanism, following recent literature. The reaction pathway followed the Waterloo’s mechanism. All models were compared with the most common solid-state reaction models using a powerful statistical tool. Activation energy of 180 kJ mol−1was found for all degradation steps, suggesting that cellulose plays a major role on Arrhenius parameters. Hemicellulose and lignin seems to affect more significantly the reaction order. The potential of the kinetic parameters for reliable prediction has been noticed due correlation coefficient above 0.99.