Wood protective coatings based on fluorocarbosilane Abstract The effectiveness of protective coatings based on 3-(2,2,3,3,4,4,5,5-octafluoropentyloxy)propyltriethoxysilane in the protection of wood surface from the effects of water was tested. No earlier attempts at using the mentioned fluorocarbosilane for the protection of wood have been reported in the literature. The coatings were deposited by the sol–gel method. As a result of the generation of chemical bonds between the wood surface and silane, a coating was produced that permanently increased the wood hydrophobicity. Fluorinated chains attached to the silicon atoms make an effective barrier preventing the access of water and limiting the effects of water on the wood surface.

Functional divergence of cellulose synthase orthologs in between wild Gossypium raimondii and domesticated G. arboreum diploid cotton species Abstract Cellulose synthase (CESA) synthesizes cellulose for plant cell walls and determines plant morphology and biomass amount. The recently sequenced cotton genomes of two diploid species, Gossypium raimondii and G. arboreum have become references for study of agriculturally important cotton fibers composed nearly exclusively of cellulose. To better understand the roles of functionally divergent CESAs, we compared physical properties and CESA expression patterns from various tissues at different developmental stages of the two diploid cottons. Chemical and phenotypic analyses showed that the domesticated G. arboreum fibers with high cellulose content, thick cell wall, and long length were superior to the wild G. raimondii fibers. Among the seventeen orthologous CESA pairs sharing > 98% identity between the two diploid genomes, putatively nonfunctional CESAs lacking structural integrity or conserved catalytic motifs were identified. Transcript expression patterns of functional CESA family genes sharing high sequence similarities in each genome were determined by RNA-seq and a PCR method that distinguished specific CESAs based on single nucleotide polymorphisms. Our results showed that mutational events causing non-functionalization and tissue specific expression patterns of the redundant CESA genes occurred in the domesticated G. arboreum more frequently than the wild G. raimondii. The results provide insight on how cellulose biosynthesis has been altered during diploid cotton evolution and domestication process, and contributed to the diversity of cotton species that differ in fiber quality and cellulose content. Graphic abstract

Polydopamine-coated cellulose nanocrystals as an active ingredient in poly(vinyl alcohol) films towards intensifying packaging application potential Abstract In this research, the dopamine self-polymerization was used to coat polydopamine (PDA) on cellulose nanocrystal (CNC) surfaces, and we integrated the functionality and structural merits of the two components in poly(vinyl alcohol) (PVA) films at a nanometer scale. The results showed that coating PDA on CNCs led to a concurrent increase in strength and break elongation. With increasing PDA@CNC loading level, the Young’s modulus continuously increased, which could be ca. 3.1-fold over that of neat PVA film at a loading level of 15 wt%. Both tensile strength and breaking elongation of the nanocomposite reached the maximum values with 6 wt% PDA@CNC, which were 75.8% and 58.1% more than those of neat PVA, respectively. Besides, the maximum decomposition temperature shifted from 271.3 °C of neat PVA film to 278.5 °C of the nanocomposite containing 6 wt% PDA@CNC, and then was continuously elevated up to 328.2 °C when the PDA@CNC loading level reached 15 wt%. For packaging application, the PDA component contributed to the UV-shielding and radical-scavenging functions, and the PDA@CNC nanofiller reduced the permeability of oxygen and water–vapor into PVA-based composites. Overall, the integrated PDA@CNC nanofiller as an active ingredient enhanced the mechanical, thermal, and functional properties of the PVA-based materials, and hence intensified the potential of their packaging application.

Synthesis of a formaldehyde-free flame retardant for cotton fabric Abstract A flame retardant ammonium salt of diethylene glycol phosphonate (ADGP) is synthesized using low-cost materials (diethylene glycol, phosphoric acid, and urea). The flame retardant is grafted on the cotton fabrics via P–O–C covalent bonds. The structure of the flame retardant is characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR). The combustion performance of the treated and untreated cotton fabrics is evaluated based on vertical flammability, limiting oxygen index (LOI), and cone calorimetry. As the concentration of the flame-retardant ADGP increased, the cotton fabric treated with 40% ADGP exhibited an LOI of 43.7% and superior fire resistance, whereas physiological comfort showed a decrease. Scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction were used to characterize the surface morphology, chemical composition, and crystal structure of the control and treated cotton fabrics. The thermal stability of the treated and untreated cotton fabrics is determined by thermogravimetric analysis. The results indicated that the treated cotton showed superior flame retardancy. Graphic abstract

Enhanced mechanical and oxygen barrier performance in biodegradable polyurethanes by incorporating cellulose nanocrystals with interfacial polylactide stereocomplexation Abstract Using bio-derived cellulose nanocrystals (CNCs) to reinforce the mechanical properties of biodegradable polyurethanes (PUs) is a promising approach especially when attempting to fabricate fully sustainable materials with high performance. However, the way to efficiently improve the dispersion and interfacial strength of CNCs in PU matrices is still an open question. In the current work, poly-l-lactide (PlLA) grafted CNCs (CNC-g-l) and a PU elastomer with poly-d-lactide as partial soft segments (d-PU) were first prepared separately, and then the fully biodegradable PU nanocomposites were fabricated by solution blending of CNC-g-l and d-PU. The surface grafting of PlLA can improve the thermal stability of CNCs, but has marginal effect on that of the nanocomposites. The improved dispersion of CNCs and enhanced interfacial strength, as evidenced by scanning electron microscopy, wide-angle X-ray diffraction and rheology measurements, are achieved by the construction of interfacial polylactide stereocomplexation (sc-PLA). The optimal improvement in mechanical properties of the nanocomposites is realized when only 1 wt% CNC-g-l is incorporated in the d-PU matrix. With the assistance of interfacial sc-PLA, the nanocomposite can gain 40% reduction in oxygen transmission rate at the optimal CNC-g-l content of 5 wt%. This study may provide a new method to improve the dispersion and interfacial strength of CNCs in biodegradable PUs and achieve simultaneously mechanical and barrier performance enhancement. Graphic abstract

Enhanced cellulase accessibility using acid-based deep eutectic solvent in pretreatment of empty fruit bunches Abstract Deep eutectic solvents (DESs) are new and rapid emerging green solvents that have been gaining much attention lately. In this work, DES was prepared by mixing choline chloride with lactic acid with the molar ratio of 1:10 to pretreat empty fruit bunches. The effects of pretreatment temperature, pretreatment time and solid-to-solvent ratio were investigated. A maximum reducing sugars yield of 51.1% was obtained at the operating conditions of 100 °C for 1 h with solid-to-solvent ratio of 1:10 (w/v). The reducing sugars yield obtained for DES pretreatment was higher than dilute acid, alkaline and organosolv pretreatment suggesting DES pretreatment is a promising alternative to conventional pretreatment techniques. Furthermore, there was no reducing sugar loss during DES pretreatment. The outstanding DES pretreatment performance was further confirmed by both Fourier-transform infrared spectroscopy and scanning electron microscopy indicated that DES pretreatment was effective in altering biomass structure by disrupting the hydrogen bonding interactions within the chains of cellulose molecules and lignin extraction. Graphic abstract

The effect of the dispersion of microfibrillated cellulose on the mechanical properties of melt-compounded polypropylene–polyethylene copolymer Abstract Microfibrillated cellulose (MFC) is a highly expanded, high surface area networked form of cellulose-based reinforcement. Due to the poor compatibility of cellulose with most common apolar thermoplastic matrices, the production of cellulose-reinforced composites in industry is currently limited to polar materials. In this study, a facile water-based chemistry, based on the reaction of MFC with tannic acid and subsequent functionalisation with an alkyl amine, is used to render the surface of the MFC fibrils hydrophobic and enhance the dispersion of the cellulose-based filler into an apolar thermoplastic matrix. The level of dispersion of the compatibilized MFC reinforced composites was evaluated using Time of Flight Secondary Ion Mass Spectrometry and multi-channel Spectral Confocal Laser Scanning Microscopy. The agglomeration of cellulosic filler within the composites was reduced by functionalising the surface of the MFC fibrils with tannic acid and octadecylamine. The resulting composites exhibited an increase in modulus at a high cellulose content. Despite the dispersion of a large portion of the functionalised filler, the presence of some remaining aggregates affected the impact properties of the composites produced.

The potential of magnetisation transfer NMR to monitor the dissolution process of cellulose in cold alkali Abstract Cellulose is the most important biopolymer on earth and, when derived from e.g. wood, a promising alternative to for example cotton, which exhibits a large environmental burden. The replacement depends, however, on an efficient dissolution process of cellulose. Cold aqueous alkali systems are attractive but these solvents have peculiarities, which might be overcome by understanding the acting mechanisms. Proposed dissolution mechanisms are for example the breakage of hydrophobic interactions and partly deprotonation of the cellulose hydroxyl groups. Here, we performed a mechanistic study using equimolar aqueous solutions of LiOH, NaOH and KOH to elucidate the dissolution process of microcrystalline cellulose (MCC). The pH was the highest for KOH(aq) followed by NaOH(aq) and LiOH(aq). We used a combination of conventional and advanced solution-state NMR methods to monitor the dissolution process of MCC by solely increasing the temperature from − 10 to 5 °C. KOH(aq) dissolved roughly 25% of the maximum amount of MCC while NaOH(aq) and LiOH(aq) dissolved up to 70%. Water motions on nanoscale timescales present in non-frozen water, remained unaffected on the addition of MCC. Magnetisation transfer (MT) NMR experiments monitored the semi-rigid MCC as a function of temperature. Interestingly, although NaOH(aq) and LiOH(aq) were able to dissolve a similar amount at 5 °C, MT spectra revealed differences with increasing temperature, suggesting a difference in the swollen state of MCC in LiOH(aq) already at − 10 °C. Furthermore, MT NMR shows a great potential to study the water exchange dynamics with the swollen and semi-rigid MCC fraction in these systems, which might give valuable insights into the dissolution mechanism in cold alkali.

Influence of urea on methyl $$\upbeta$$β -D-glucopyranoside in alkali at different temperatures Abstract The dissolution efficiency plays an important role on the properties of regenerated cellulose-based products. Urea is known to be one of the additives aiding to improve cellulose dissolution in the NaOH(aq) system. The acting mechanism caused by urea has been debated and one of the hypothesis is that urea could induce a conformational change on cellulose, which promotes dissolution. Here we used NMR spectroscopy on a model system for cellulose, namely, methyl \(\upbeta\)-D-glucopyranoside (\(\upbeta\)-MeO-Glcp) and compared chemical shifts and J couplings, which both are indicators for conformational changes, as a function of temperature and upon the addition of urea. We found that in NaOH(aq), the hydroxymethyl group changes its conformation in favour of the population of the gt rotamer, while the presence of urea induced temperature dependent conformational changes. Heteronuclear Overhauser effect experiments showed that urea associates with cellulose but in a non-specific manner. This suggests that urea rather than binding to the carbohydrate, changes the chemical environment inducing a change in conformation of \(\upbeta\)-MeO-Glcp and likely also for cellulose when dissolved in NaOH(aq) with urea.

Production of hydroxyapatite–bacterial cellulose composite scaffolds with enhanced pore diameters for bone tissue engineering applications Abstract Bone tissue engineering scaffolds used for the treatment of bone defects are required to be osteoconductive, osteoinductive, osteogenic, biocompatible, and have enough porosity to allow osteointegration, as well as vascularization. It is known that addition of the hydroxyapatite (HAp) to bone tissue scaffolds promotes bone formation by increasing osteoconductivity. Bacterial cellulose (BC) is a highly biocompatible material, and its mechanical properties and fibrous structure allow that it can be used as a bone tissue scaffold; yet, the nano-porous structure of BC (50–200 nm) prevents or limits cell migration and vascularization. In this study, it is intended to take advantage of the porous structure and mechanical strength of BC and osteoconductive properties of HAp for the production of tissue engineering scaffolds. Pore sizes of BC were enhanced to 275 μm by a novel shredded agar technique, and SaOs-2 cells were shown to migrate between the fibers of the modified BC. It was observed that mineralization of SaOs-2 cells was enhanced on in situ produced HAp-BC nano-composites compared to BC scaffolds. Graphic abstract