ALBERT

Description: Two dimensional (2D) nanocrystals of noble metals (e.g., Au, Ag, Pt) often have unique structural and environmental properties which make them useful for applications in electronics, optics, sensors and biomedicines. In recent years, there has been a focus on discovering the fundamental mechanisms which govern the synthesis of the diverse geometries of these 2D metal nanocrystals (e.g., shapes, thickness, and lateral sizes). This has resulted in being able to better control the properties of these 2D structures for specific applications. In this review, a brief historical survey of the intrinsic anisotropic properties and quantum size effects of 2D noble metal nanocrystals is given and then a summary of synthetic approaches to control their shapes and sizes is presented. The unique properties and fascinating applications of these nanocrystals are also discussed.

Description: Esterification was used to improve the thermal stability of nanocellulose to extend its application as reinforcing filler to polymer matrices with high melting point. The effect of the structure of ester groups on thermal stability was studied in detail. Various types of nanocellulose esters (straight-chain, C2–C14; cyclic adamantoyl, ADM; aromatic benzoyl, BNZ; and branched pivaloyl, PIV) with degree of substitution values in the range of 0.40–0.47 were prepared from bacterial cellulose nanofibers and nanocrystals. The reaction conditions used to prepare the esters maintained the viscosity-average degree of polymerization (DPv) and crystallinity of the starting materials. Thermogravimetric analysis showed that the temperature at maximum weight loss rate (T max ) increased after esterification. The structure of the ester groups and the DPv, however, showed no varying effect on T max . The 5 % weight loss temperature (WLT) which was used to assess the thermal stability at the onset of thermal degradation varied with the type of ester. Lower 5 % WLT was observed in straight-chain esters than those of the bulky esters of ADM, BNZ and PIV; which also showed high resistance to weight loss when subjected to isothermal heating. To understand the event at the onset of thermal degradation, low temperature pyrolysis was conducted. The evolved gases were separated and identified by gas chromatography–mass spectrometry technique. Results showed that at the onset of thermal degradation, levoglucosan (LG) is produced from the untreated BC nanocrystals. After esterification, LG formation was inhibited. The removal of the ester groups or deprotection is the main event at the onset of thermal degradation of nanocellulose esters. From the structure of the pyrolysis products, the mechanism of thermal deprotection of nanocellulose esters is proposed for the first time.

Description: Sugar palm fiber (SPF) is one of the prospective fibers used to reinforce polymer composites. The aim of this study is to evaluate the physicochemical, thermal, and morphological properties of SPF after alkali and sea water treatments. The chemical constituents group and thermal stability of the SPF were determined using scanning electronic microscopy (SEM) along with energy dispersive X-ray spectroscopy and thermogravimetric analysis (TGA). Fourier transform infrared spectroscopy was carried out to detect the presence of functional groups in untreated and treated SPF. The SEM images after both treatments showed that the external surface of the fiber became clean as a result. However, the sea water treatment affected the fiber properties physically, while the alkali treatment affected it both physically and chemically by dissolving the hemicellulose in the fiber. The TGA results showed that untreated fiber is significantly more stable than treated fiber. In conclusion, the results show that the fiber surface treatment significantly affected the characterization of the fiber.

Description: Viscose fiber was oxidized with sodium periodate to prepare a reactive dialdehyde viscose fiber (DAVF) containing abundant aldehyde groups. A solid amine adsorbent (DAVF-PEI) with high amino density for CO 2 capture was then prepared by modifying DAVF with polyethylenimine (PEI). Response surface methodology (RSM) based on a three-level, three-factorial design was used to optimize the synthesis conditions of DAVF, in which multiple linear regression equations of aldehyde content and fiber mass loss degree were constructed. The well-designed DAVF was then employed as a support to graft with PEI via Schiff base reaction to prepare a solid amine fiber (DAVF-PEI) for CO 2 adsorption. The experimental results verified that DAVF-PEI possessed good thermo-stability and high CO 2 adsorption capacity (4.11 mmol/g). DAVF-PEI also showed promising regeneration performance, which could maintain almost the same adsorption capacity for CO 2 after ten adsorption and desorption recycles.

Description: Encapsulation of various materials on textiles is an interesting task because of the controlled release and higher stability. Here, a robust cotton fabric was prepared through novel simultaneous treatment and nano-encapsulation of Chamomile extract using Tragacanth gum (TG) as the wall material and an environmentally friendly binder with hydrogel properties. The nano-encapsulated and treated cotton (NE&TC) fabric was characterized by FESEM, FT-IR and UV-Vis spectrophotometry, which indicated the successful encapsulation of the plant extract within the TG and material and linkage on the cotton fabric. The peaks at 1736 and 1777 cm −1 related to the TG and Chamomile extract in the FT-IR spectrum and a strong peak around 270–400 nm in the UV-Vis spectrum of the NE&TC fabric confirmed the nano-encapsulation and treatment. The prepared NE&TC fabric indicated a relatively good washing and rubbing durability with reasonable release behavior. The DSC pattern of the NE&TC fabric showed a peak at 162 °C confirming the presence of  Chamomile extract in the nanocapsules. This article proposes a novel method for the application of TG as a natural polymer on cotton fabric for obtaining multifunction purposes including in-situ synthesis of encapsulated Chamomile extract, stabilization of nanocapsules and introduction of hydrogel properties.

Description: Recyclable and transparent nanocomposite films based on bacterial cellulose (BC) and hemiaminal dynamic covalent network polymer (HDCN) have been synthesized by in situ polymerization of 4,4′-diaminodiphenyl ether (ODA) with paraformaldehyde. Transparency and structural and mechanical properties of such nanocomposite films are investigated. It was found that BC/HDCN nanocomposite films exhibits a high optical transparency (86 % at 550 nm). Scanning electron microscopy reveals excellent compatibility of the reinforcement of BC nanofibers and HDCN matrix, which leads to the improvement of 20 and 200 % in tensile strength and storage modulus, respectively, as compared to neat HDCN films. BC hydrogels are readily recoverable from nanocomposite films by the sulphuric acid treatment and ODA monomer is deposited and also recycled.

Description: This article describes a facile route, which combines mild maceration of waste pulp sludge and a mechanical shearing process, to prepare microfibrillated cellulose (MFC) with a high storage modulus. In the maceration, the mixture of glacial acetic acid and hydrogen peroxide was used to extract cellulose from never-dried waste pulp sludge. Then, two different mechanical processes including disc refining (DR) and ultrasonication plus homogenization (UH) were applied to the cellulose after maceration and resulted in MFC with a highly tangled fibril network. All of the resultant cellulosic suspensions (2 % w/w) exhibited a gel-like and shear-thinning behavior with storage moduli ( G ′) ranging from 200 to 4000 Pa. Among them, the 30-min DR-treated MFC gels had the maximum G ′, which was much higher than for previously reported MFC gels at the same concentration. Additionally, after mechanical processing, specific surface areas and water retention values of MFC were accordingly increased with the enhancement of shear force, while the storage moduli ( G ′) were not consistently increased. Finally, a strong MFC gel was successfully prepared from never-dried waste pulp sludge via a one-step disc refining process and using cost-effective chemicals. The obtained hydrogels will have potential as low-density reinforcing fillers or as a template for further surface modification.

Description: A kind of viscose fiber fabric with permanent flame retardancy has been prepared by grafting polymerization of phosphorus and nitrogen-containing monomer, i.e. 2,2-dimethyl-1,3-propanediol acrylamide methoxyl phosphate (DPAMP) onto viscose fiber fabric (VF-g-DPAMP). The effects of the initiator concentration, DPAMP concentration, temperature, pH and time on grafting polymerization were studied, and the structure of VF-g-DPAMP was determined with Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy. The surface morphology of viscose fiber fabric and VF-g-DPAMP were studied by scanning electron microscope. The thermal property and fire retardant performance of VF-g-DPAMP were assessed by thermogravimetric analysis, limited oxygen index measurements and cone calorimeter test, respectively. The results show that DPAMP has been successfully grafted onto viscose fiber fabric, and VF-g-DPAMP has good char-forming ability and better fire retardancy. The pkHRR and THR of the grafted fabric decrease from 150 to 98 kW/m 2 and 5.70 to 1.73 MJ/m 2 , respectively.

Description: Foamable high melt strength polypropylene (HMSPP) was prepared by grafting styrene (St) onto polypropylene (PP) and simultaneously introducing polydimethylsiloxane (PDMS) through a one-step melt extrusion process. The effect of PDMS viscosity on the foaming behavior of HMSPP was systematically investigated using supercritical CO 2 as the foaming agent. The results show that the addition of PDMS has little effect on the grafting reaction of St and HMSPP exhibits enhanced elastic response and obvious strain hardening effect. Though the CO 2 solubility of HMSPP with PDMS (PDMS-HMSPP) is lower than that of HMSPP without PDMS, especially for PDMS with low viscosity, the PDMS-HMSPP foams exhibit narrow cell size distribution and high cell density. The fracture morphology of PDMS-HMSPP shows that PDMS with low viscosity disperses more easily and uniformly in HMSPP matrix, leading to form small domains during the extrusion process. These small domains act as bubble nucleation sites and thus may be responsible for the improved foaming performance of HMSPP.

Description: Paper-based devices enable low-cost mass production, wide availability and useful technical aspects such as light weight, mechanical bendability and natural integration in existing paper-based creations such as educational books, administrative documentation and artwork. While magneto-electronics and spintronics play an important role in delivering sensing, communication and data storage solutions, especially necessary in the framework of the internet of things, it is beneficial to achieve compatibility between this technology and paper materials. As a first example of paper-based magneto-electronics, we investigate the manufacturing of well performing anisotropic magneto-resistors on paper by means of low power sputter deposition of permalloy \((\hbox {Py:Ni}_{81}\hbox {Fe}_{19})\) , shadow mask patterning and magnetic clamping of the shadow mask. A range of commercially available papers were studied by varying most significant mechanical, chemical and geometrical attributes of the paper to this application. The dependence of magnetic properties (coercivity, saturation remanence and relative permeability) on the paper properties (surface roughness, stiffness and paper making process) was studied based on magnetic characterization, surface profilometry and elemental analysis. Subsequently, conclusions on the optimal magnetic \(\hbox {Py:Ni}_{81}\hbox {Fe}_{19}\) -on-paper system were drawn.

Description: In this work, wheat bran was used as cellulosic filler in biocomposites based on natural rubber. The impact of wheat bran content [ranging from 10 to 50 parts per hundred rubber (phr)] on processing, structure, dynamic mechanical properties, thermal properties, physico-mechanical properties and morphology of resulting biocomposites was investigated. For better characterization of interfacial interactions between natural rubber and wheat bran, achieved results were compared with properties of biocomposites filled with commercially available cellulosic fillers—wood flour and microcellulose. It was observed that wheat bran, unlike commercial cellulosic fillers, contains high amount of proteins, which act like plasticizers having profitable impact on processing, physical, thermo-mechanical and morphological properties of biocomposites. This is due to better dispersion and distribution of wheat bran particles in natural rubber, which results in reduction of stiffness and porosity of the biocomposites. Regardless of cellulosic filler type, Wolff activity coefficient was positive for all studied biocomposites implying reinforcing effect of the applied fillers, while tensile strength and elongation at break decreased with increasing filler content. This phenomenon is related to restricted strain-induced crystallization of NR matrix due to limited mobility of polymer chains in the biocomposites. Furthermore, this explains negligible impact of particle size distribution, chemical composition and crystallinity degree of applied cellulosic filler on static mechanical properties of highly-filled NR biocomposites. The conducted investigations show that wheat bran presents interesting alternative for commercially available cellulosic fillers and could be successfully applied as a low-cost filler in polymer composites.

Description: Guar gum (GG) fracturing fluids were studied by incorporating cellulose nanofibrils (CNFs) in anhydrous borax crosslinked guar gum gels. To fully understand the impact of CNF on the proppant suspension capability of developed fracturing fluids, their shear rate-dependent viscosity and viscoelasticity were investigated. The shear rate dependencies of fluids was fitted to the Carreau model. The zero shear rate viscosity and elasticity of fracturing fluids increased significantly by incorporating CNF in guar gum gels. On the other hand, the viscosity at high shear rates (〉100 s −1 ) decreased as desired. The proppant settling velocities through fracturing fluids were evaluated by modeling the terminal falling velocity of proppants moving through a Carreau model fluid. The experimental results of the rheological behavior and the modeling results of the proppant settling rate indicated that the fracturing fluids containing CNF had better suspension capabilities. In addition, the lower viscosities of CNF formulated GG gels at higher shear rates will make them more pumpable.

Description: Novel cellulose–chitosan nanocomposite particles with spherical shape were successfully prepared via mixing of aqueous biopolymer solutions in three different ways. Macroparticles with diameters in the millimeter range were produced by dripping cellulose dissolved in cold LiOH/urea into acidic chitosan solutions, inducing instant co-regeneration of the biopolymers. Two types of microspheres, chemically crosslinked and non-crosslinked, were prepared by first mixing cellulose and chitosan solutions obtained from freeze thawing in LiOH/KOH/urea. Thereafter epichlorohydrin was applied as crosslinking agent for one of the samples, followed by water-in-oil (W/O) emulsification, heat induced sol–gel transition, solvent exchange, washing and freeze-drying. Characterization by X-ray photoelectron spectroscopy, total elemental analysis, and Fourier transform infrared spectroscopy confirmed the prepared particles as being true cellulose–chitosan nanocomposites with different distribution of chitosan from the surface to the core of the particles depending on the preparation method. Field emission scanning electron microscopy and laser diffraction was performed to study the morphology and size distribution of the prepared particles. The morphology was found to vary due to different preparation routes, revealing a core shell structure for macroparticles prepared by dripping, and homogenous nanoporous structure for the microspheres. The non-crosslinked microparticles exhibited a somewhat denser structure than the crosslinked ones, which indicated that crosslinking restricts packing of the chains before and under regeneration. From the obtained volume-weighted size distributions it was found that the crosslinked microspheres had the highest median diameter. The results demonstrate that not only the mixing ratio and distribution of the two biopolymers, but also the morphology and nanocomposite particle diameters are tunable by choosing between the different routes of preparation.

Description: Gram’s Iodine Assay is currently used to detect endoglucanase, a cellulase enzyme which cleaves β-1,4-glycosidic bonds in carboxymethylcellulose (CMC). When a zone of degradation was observed around non-cellulolytic Escherichia coli JM109 with the use of Gram’s Iodine, the assay was further examined. Additional cellulolytic bacteria were chosen to display these inconsistencies. Bacillus thuringiensis subsp. Kurstaki ( Btk ) and Cellulomonas persica , known to possess endoglucanase, were incubated at 30 °C for 48 h on several different media; 1.5 % agar only, Davis minimal media, CMC agar, non-CMC agar, and Phytagel CMC. After the incubation period all plates were flooded with Gram’s Iodine for 3–5 min. A clear ring of degradation was identified around colonies in plates containing no cellulose and plates containing agar only. When agar was removed as the solidifying agent and substituted with Phytagel, zones of clearing around cellulolytic organisms were altered. These findings indicate that agar alone can cause additional artifacts and should be replaced by other solidifying agents as well as supplementation of the Congo Red Assay. Taking these precautions can overcome inconsistency problems for future cellulolytic screenings.

Description: Microcrystalline cellulose (MCC) was modified with pyridone derivatives such as pyridone diester (PDE) and pyridone diacid (PDA) by using succinic acid anhydride as a linker. The modified MCCs were characterized by the fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric analysis, elemental analysis and solid state 13 C NMR. The adsorption capacities of the modified MCCs to cationic dyes were examined by using methylene blue (MB) as a model dye. It was found that the kinetic adsorption data followed the pseudo-second-order kinetic model, and the adsorption equilibriums were reached less than 10 min. The isothermal adsorption data were fitted with the Langmuir isotherm model very well, from which the maximum adsorption capacities of the MCCs modified with PDE and PDA were determined to be 101.01 and 142.86 mg/g, respectively. Further investigation showed that the modified MCCs were pH-dependent for adsorption of MB in aqueous solutions. The modified MCCs could be used for removal of MB from an aqueous solution at pH 8, and reused by regeneration in an acidic solution. It was tested that the modified MCCs had a high reusability for removal of MB from aqueous solutions, and still maintained high adsorption capacities even after multiple cycles of desorption–adsorption processes. Hence, the MCCs modified with PDE and PDA could be an effective and efficient approach to removal of cationic dyes from aqueous solutions.

Description: Cardanol is a biobased raw material derived from cashew nut shell liquid. In order to extend its utility, new derivatives and additional applications are useful. In this work cardanol was first epoxidized, and a novel aniline derivative prepared from it under mild reaction conditions with the help of an ionic liquid catalyst. The reaction chemistry was studied by using nuclear magnetic resonance. The resulting aminohydrin adduct showed antioxidant property and should also be a useful synthon for further reactions. As an example, the aminohydrin was shown to undergo a condensation reaction with formaldehyde to form a prepolymer, which could be further reacted to form thermosetting resins.

Description: Silver nanoparticles (AgNPs) have been synthesized in the presence of polyacrylate through the reduction of silver nitrate by sodium borohydride in aqueous solution. The AgNO3 and polyacrylate carboxylate group concentrations were kept constant at 2.0 × 10 –4 and 1.0 × 10 –2 mol·L –1 , respectively, while the ratio of [NaBH 4 ]/[AgNO 3 ] was varied from 1 to 100. The ultraviolet-visible plasmon resonance spectra of these solutions were found to vary with time prior to stabilizing after 27 d, consistent with changes of AgNP size and distribution within the polyacrylate ensemble occurring. These observations, together with transmission electron microscopic results, show this rearrangement to be greatest among the samples at the lower ratios of [NaBH 4 ]/[AgNO 3 ] used in the preparation, whereas those at the higher ratios showed a more even distribution of smaller AgNP. All ten of the AgNP samples, upon a one thousand-fold dilution, catalyze the reduction of 4-nitrophenol to 4-aminophenol in the temperature range 283.2–303.2 K with a substantial induction time being observed at the lower temperatures.

Description: Chemical cationization of cotton has been a subject of increased interest due to the ability of cationized cotton to attract negatively charged dyes, thus eliminating the use of electrolytes during dyeing and increasing color yield. However, electrostatic attractions between cationized cotton and anionic dyes also result in significantly increased dye strike rates, which may cause levelness problems, especially when light to medium shades are required. In this study, cotton fabric cationized using 3-chloro-2-hydroxypropyl trimethylammonium chloride was used to investigate the method for obtaining appropriate dye strike rate to produce a level reactive dyeing on cationized cotton. To effectively control the dyeing kinetics of reactive dyes on cationized cotton, real-time exhaustion of six commercially significant reactive dyes were monitored. The influence of temperature, dye structure, and addition of soda ash on dyeing kinetics and levelness of cationized cotton were evaluated.

Description: Cotton woven fabrics were first dyed with a graphene oxide (GO) aqueous dispersion using a simple industrialized exhaustion dyeing process. The resulting fabrics were then chemically reduced to prepare the electrically conductive cotton fabrics. They were characterized by the FE-SEM, XPS and Raman spectrum and evaluated with respect to whiteness, electrical surface resistance and electrochemical impedance spectroscopy. Some factors affecting the process such as the GO concentration, dyeing and reducing conditions, and nature and concentration of the reducing agent were also investigated. The results indicated that GO could be fixed on cotton fabric by a simple exhaustion dyeing process and converted into the reduced GO (RGO) with a reducing agent. Increasing the GO concentration or dyeing temperature and time decreased the whiteness and electrical surface resistance of the RGO-dyed fabric. However, higher pH showed a reverse effect. Na 2 S 2 O 4 was found to be a stronger reducing agent for the conversation of GO into RGO on cotton fabric than ascorbic acid and thiourea. The reduction of GO-dyed fabric was easily completed by an increasing Na 2 S 2 O 4 concentration at higher temperature. Moreover, an increasing number of dyeing cycles decreased the surface resistance and impedance modulus and increased the abrasion resistance of the RGO-dyed cotton fabric.

Description: Surface functionalization of textiles is crucial in developing protective clothing that protects wearers from potential hazards of liquid, chemical and biological contamination. This study aims to explore chemical and water protective surface on cotton fabric by pad-knife-pad coating of waterborne polyurethane (WPU), polydimethylsiloxane (PDMS) and trimethylated silica (TMS). The chemical structure of the coated cotton fabrics was characterized by attenuated total reflectance Fourier transform infrared spectroscopy. Surface wettability and liquid protective properties of the coated cotton fabrics were analyzed by water contact angle, water repellency, hydrostatic pressure, and oil and aqueous liquid repellency. It was revealed that WPU and PDMS-TMS formed copolymerization reactions, resulting in ultrahydrophobic, oil repellent and mechanically strong membrane on the surface of cotton fabric. It has been found that the coating of WPU-PDMS-TMS makes cotton fabric highly resistant to water, oil and aqueous liquids. This surface functionalization technology can be further applied in developing protective clothing with chemical and water resistant and self-cleaning properties.

Description: While drug resistance appears to be an inevitable problem of an increasing number of anticancer drugs in monotherapy, combination drug therapy has become a prosperous method to reduce the administered total drug dosages as well as overcome the drug resistance of carcinoma cells. Curcumin, considered to possess multifaceted roles in cancer treatment according to its multiple anti-neoplastic mechanisms as a depressor of chemoresistance, can significantly facilitate its anti-cancer functions and improve therapeutic effects via combination usage with a variety of other drugs with different reaction mechanisms. To explore this possibility, four anti-cancer chemotherapeutic agents that all possess a certain degree of drug resistance problems, including three tyrosine kinase inhibitors (erlotinib, sunitinib and sorafenib) that are acting on different cell pathways and a typical anticancer drug doxorubicin, were combined with curcumin individually to examine the synergistic anti-tumor effect both in vitro and in vivo . Results revealed that sunitinib combined with curcumin at the molar ratio of 0.46 yielded the most potent synergistic effect in vitro , and was therefore chosen for further animal evaluation. To further enhance the anticancer effect, bovine serum albumin (BSA) nanoparticles were utilized as a carrier to deliver the selected drug combination in situ . Preliminary in vivo findings confirmed our hypothesis of being able to maintain a similar injected drug ratio for prolonged time periods in tested animals by our approach, thereby maximizing the therapeutic potency yet minimizing the toxicity of these drugs. This work could open up a new avenue on combination drug therapy and realization the clinical utility of such drugs.

Description: Though research into nanofibrillated cellulose (NFC) has recently increased, few studies have considered co-utilising NFC and nanographite (NG) in composite films, and, it has, however been a challenge to use high-yield pulp fibres (mechanical pulps) to produce this nanofibrillar material. It is worth noting that there is a significant difference between chemical pulp fibres and high-yield pulp fibres, as the former is composed mainly of cellulose and has a yield of approximately 50 % while the latter is consist of cellulose, hemicellulose and lignin, and has a yield of approximately 90 %. NFC was produced by combining TEMPO (2,2,6,6-tetramethypiperidine-1-oxyl)-mediated oxidation with the mechanical shearing of chemi-thermomechanical pulp (CTMP) and sulphite pulp (SP); the NG was produced by mechanically exfoliating graphite. The different NaClO dosages in the TEMPO system differently oxidised the fibres, altering their fibrillation efficiency. NFC–NG films were produced by casting in a Petri dish. We examine the effect of NG on the sheet-resistance and mechanical properties of NFC films. Addition of 10 wt% NG to 90 wt% NFC of sample CC2 (5 mmol NaClO CTMP-NFC homogenised for 60 min) improved the sheet resistance, i.e. from that of an insulating pure NFC film to 180 Ω/sq. Further addition of 20 (CC3) and 25 wt% (CC4) of NG to 80 and 75 wt% respectively, lowered the sheet resistance to 17 and 9 Ω/sq, respectively. For the mechanical properties, we found that adding 10 wt% NG to 90 wt% NFC of sample HH2 (5 mmol NaClO SP-NFC homogenised for 60 min) improved the tensile index by 28 %, tensile stiffness index by 20 %, and peak load by 28 %. The film’s surface morphology was visualised using scanning electron microscopy, revealing the fibrillated structure of NFC and NG. This methodology yields NFC–NG films that are mechanically stable, bendable, and flexible.

Description: Highly water-soluble cyclosophoraose (Cys) has been recently used as a suitable complexation agent to enhance the solubility of drugs that are hardly water-soluble by molecular encapsulation via host–guest complexation. In this study, a novel Cys/cellulose hydrogel was prepared by cross-linking Cys and cellulose for efficient galangin delivery to improve antibacterial activity. Galangin was known to directly inhibit the activity of β-lactamase and to exhibit intrinsic antibacterial activity. The inhibition of β-lactamase by galangin was also known to enhance the eradication of a strain of methicillin-resistant Staphylococcus aureus . However, efficient delivery of galangin in an aqueous solution for improved antibacterial activity could not be achieved because of its extremely poor water solubility and bioavailbility. The structure and morphology of the resulting hydrogels were verified using with various instrumental techniques using rheometer, FT-IR spectroscopy, solid-state NMR spectroscopy, XRD and FE-SEM. The loading amount of galangin increased as the Cys content in the hydrogels increased, with a release time of 48 h. The galangin loading amount and its cumulative amount released from the Cys/cellulose hydrogel were 1.62- and 1.64-fold greater than those of galangin released from cellulose hydrogel, respectively. Additionally, the galangin-loaded Cys/cellulose hydrogel had antibacterial activity against S. aureus , with growth inhibition maintained up to 72 h. Furthermore, the Cys/cellulose hydrogel did not show any cytotoxicity toward human dermal fibroblasts. Throughout the study, the Cys/cellulose hydrogel demonstrated potential advantages as an efficient antibacterial dressing material for galangin delivery through targeting of drugs to the wound site in a sustained manner over a long period without frequent dressing changes.

Description: The extensional flow behaviors of cellulose/NaOH/urea/H 2 O solution were investigated by using capillary breakup extensional rheometry (CaBER). The effects of temperature, storage time and cellulose concentrations on both the storage modulus G ′ and the loss modulus G ″ were also analyzed. For 2 wt% cellulose solution, the G ′, G ″ and filament lifetime remained unchanged after long storage time. While, for 4 wt% cellulose solution, physical gels could form at either higher temperature or for longer storage time, and the filament lifetime, the relaxation time ( λ e ) and the initial extensional viscosity ( η e 0 ) first increased and then decreased with increase of the storage time. The transition points of the filament lifetime shifted to lower storage time with the increase of the temperature. The η e 0 is proportional to λ e . The results presented suggest that the extensional properties of the cellulose/NaOH/urea/H 2 O solution first increase and then decrease during the gelation process, and the spinning time, which decreases linearly with the increase in the storage temperature, must be controlled below the time that η e 0 starts to decrease.

Description: A novel preparation route of zinc oxide (ZnO)–cellulose composite was developed via synthesis of ZnO in partially dissolved cellulose. Filter paper was partially dissolved in zinc chloride (ZnCl 2 ) solution. Then, the ZnO–cellulose composite was achieved when the partially dissolved cellulose was reacted with sodium hydroxide (NaOH) solution. Several factors affecting the ZnO content and mechanical properties of the composite were investigated. The ZnO–cellulose composite was characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and energy dispersive X-ray spectroscopy. Compared to the untreated paper, the ZnO–cellulose composite had high compactness. Meanwhile, its tensile strength and folding strength were improved two times and fifteen times, respectively. Cellulose fibers treated with this method had the skeleton of un-dissolved cellulose fibers, the matrix of gelled cellulose, and flower-like ZnO nanoplate on cellulose surface. In addition, the antibacterial property was identified from the ZnO–cellulose composite.

Description: Wood pulp cellulose nanofibrils (CNF) thin film is a novel recyclable and biodegradable material. We investigated the microwave dielectric properties of the epoxy coated-CNF thin film for potential broad applications in flexible high speed electronics. The characterizations of dielectric properties were carried out in a frequency range of 1–10 GHz. The dielectric constant and loss tangent were extracted by using measurements of microstrip transmission lines that were built on the epoxy coated-CNF film and combined with Agilent Advanced Design System simulations. The RF property for the epoxy coated-CNF was compared to that of commercial polyethylene terephthalate film (PET). With the comparable microwave properties of non-biodegradable PET film, our study suggests that the epoxy coated-CNF film is a suitable biodegradable and environment-friendly substrate for flexible microwave and other applications.

Description: In recent years, nanofibrous mats derived from biopolymers have attracted more interest and attention for biomedical applications, such as wound dressing, tissue engineering, and drug delivery. In this study, carboxymethyl cellulose/Ag nanoparticles (CMC/Ag NPs) nanofibrous membranes were prepared via a simple and green method in which electrospun CMC/poly(ethylene oxide) membranes were immersed in AgNO 3 solution, followed by reduction of Ag + –Ag NPs upon ultraviolet (UV) irradiation. Notably, as evidenced by Fourier-transform infrared (FTIR), X-ray diffraction (XRD), and thermogravimetric (TG) analyses, poly(ethylene oxide) was eliminated during the immersion process and CMC nanofibrous mats containing Ag NPs were obtained. The effects of UV wavelength, AgNO 3 solution concentration, and irradiation time on the morphology of the CMC/Ag NPs membranes were investigated, revealing optimal parameters (254 nm wavelength, 0.1 mol/L AgNO 3 solution, and 10 min irradiation time) under which Ag NPs with average diameter of 20 nm were uniformly distributed on the surface of fibers. Antibacterial tests indicated that the antibacterial efficiency against Escherichia coli and Staphylococcus aureus of the obtained CMC/Ag NPs membranes reached up to 100 %, suggesting great potential for use as antimicrobial dressings.

Description: Sago seed shells are agricultural wastes that are discarded after taking the pith. The composition of sago seed shells has been determined by using standard methods. Parameters such as extractives (ASTM D1107-96), Klason lignin (ASTM D1106-96), holocellulose (Wise et al. in Paper Trade J 122(2):35–42, 1946 ), α-cellulose (ASTM D 1103-60), hemicellulose (by difference) and ash content (T 211 om 02) were determined. The components were characterised using FTIR, TGA, XRD, SEM, TEM and AFM. The detailed spectral, thermal, XRD and SEM analyses show the presence Klason lignin, holocellulose and α-cellulose. α-Cellulose has been converted into microcrystalline cellulose (MCC) by acid hydrolysis. MCC was also characterised by using FTIR, TGA, XRD, SEM, TEM and AFM. Frequencies of the FTIR spectrum are similar to those of α-cellulose, and the TGA data reveal increased decomposition temperatures for MCC and well as a well defined TGA curve, indicating the increased structural order or crystallinity. This is further supported by XRD. SEM, TEM and AFM results, which reveal the microstructural behavior of isolated MCC.

Description: The drive towards sustainability, even in materials technologies, has fuelled an increasing interest in bio-based composites. Cellulosic fibres, such as flax and jute, are being considered as alternatives to technical synthetic fibres, such as glass, as reinforcements in fibre reinforced polymer composites for a wide range of applications. A critical bottleneck in the advancement of plant fibre composites (PFRPs) is our current inability to predict PFRP properties from data on fibre properties. This is highly desirable in the cost- and time-effective development and design of optimised PFRP materials with reliable behaviour. This study, alongside limited other studies in literature, have found that the experimentally determined (through single fibre tests) fibre properties are significantly different from the predicted (‘back-calculated’ using the popular rule-of-mixtures) fibre properties for plant fibres. In this note, we explore potential sources of the observed discrepancy and identify the more likely origins relating to both measurement and errors in predictions based on the rule-of-mixtures. The explored content in this discussion facilitates the design of a future investigation to (1) identify the sensitivity of the discrepancy between measured and predicted fibre properties to the various potential origins, (2) form a unified hypothesis on the observed phenomenon, and (3) determine whether the rule-of-mixtures model (in specific cases) can be improved and may be able to predict properties precisely.

Description: Enzymatic hydrolysis of cellulose provides a renewable source of monosaccharides for production of variety of biochemicals and biopolymers. Unfortunately, the enzymatic hydrolysis of cellulose is often incomplete, and the reasons are not fully understood. We have monitored enzymatic hydrolysis in terms of molecular density, ordering and autofluorescence of cellulose structures in real time using simultaneous CARS, SHG and MPEF microscopy with the aim of contributing to the understanding and optimization of the enzymatic hydrolysis of cellulose. Three cellulose-rich substrates with different supramolecular structures, pulp fibre, acid-treated pulp fibre and Avicel, were studied at microscopic level. The microscopy studies revealed that before enzymatic hydrolysis Avicel had the greatest carbon-hydrogen density, while pulp fibre and acid-treated fibre had similar density. Monitoring of the substrates during enzymatic hydrolysis revealed the double exponential SHG decay for pulp fibre and acid-treated fibre indicating two phases of the process. Acid-treated fibre was hydrolysed most rapidly and the hydrolysis of pulp fibre was spatially non-uniform leading to fractioning of the particles, while the hydrolysis of Avicel was more than an order of magnitude slower than that of both fibres.

Description: Four sources of cellulose with different molecular weights were dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate at 100 °C over a 10 h period. The solution densities were determined and these results were subsequently utilised to access the influence of dissolved cellulose on surface tension properties of cellulose/ionic liquid solutions. Surface tension measurements revealed increasing molecular weight and concentration reduced surface tension while temperature increases showed the opposite effect. These results are consistent with that of repulsive polymer-wall interactions near the interface in good solvent conditions. The semi-flexible nature of this carbohydrate in solution can help explain deviations of these results when compared to ideal flexible chains.

Description: Preparation of nanocrystalline cellulose (NCC) by 62 and 65 % wt. sulfuric acid hydrolysis of cellulase-pretreated fibers was optimized to obtain the highest yield by applying two statistical plans. At optimal conditions (10 U/g odp cellulase, 25 min hydrolysis, 47 °C, 62 wt.% H 2 SO 4 ), high yields (≥80 %) were obtained, including an increase of ~9 points due to the enzyme. Optimal conditions produced nanosized particles of around ~200 nm with reduced surface charge and sulfur content. The optimization allowed reduction of hydrolysis time by 44 % and increase of yield by more than 10 points compared with results in previous work. The effects of cellulase pretreatment were noticeable even under aggressive hydrolysis conditions, emphasizing its possibilities. Zeta potential and polydispersity index indicated that all studied conditions led to good-quality final products, with values around −50 mV and 0.2, respectively. Transmission electron microscopy (TEM) analysis confirmed the presence of NCC. Fourier-transform infrared (FTIR) spectroscopic analysis provided evidence that cellulase treatment increased the crystallinity of both cellulose fibers and NCC, as well as fiber accessibility, supporting the other analyses of NCC.

Description: Porous sheets with high mechanical strength were prepared with natural pulp fibers (hardwood and softwood bleached kraft pulp) and polyethylene terephthalate (PET) by adding cellulose nanofibrils (CNF) through a wet-laid forming method. The structure and mechanical properties of the porous sheets were investigated in this study depending on the type of mixed fibers, the CNF ratio, and drying methods (cylinder-drying and freeze-drying). The apparent density and porosity of porous sheets changed according to the morphology of the mixed fibers. PET fibers resulted in a sheet with a bulkier structure, whereas natural pulp fibers produced relatively dense sheets. Sheets with high porosity could be prepared by freeze-drying due to the inhibition of hydrogen bonds and low shrinkage during drying. Pore characteristics were evaluated in terms of air permeability and average pore diameter. The air permeability of porous sheets decreased as the amount of CNF increased. Mercury porosimetry showed that the average pore diameter in sheets ranged from 0.6 to 36.7 µm depending on the type and mixing ratio of fibers and drying conditions. Sheet tensile properties were improved by the addition of CNF and changed depending on mixing combinations and drying methods. The applicability of freeze-dried porous sheets as filter media was examined by evaluating the filtration efficiency and pressure drop. Porous sheets with a HwBKP/CNF combination showed a filtration efficiency of 99.944 %, which approached the efficiency of a high efficiency particulate air filter. However, further study is required to reduce the pressure drop during filtration for better use as an air filter.

Description: Modeling structural and thermodynamic properties of nucleic acids has long been a challenge in the development of force fields. Polarizable force fields are a new generation of potential functions to take charge redistribution and induced dipole into account, and have been proved to be reliable to model small molecules, polypeptides and proteins, but their use on nucleic acids is still rather limited. In this article, the interactions between nucleic acids and a small molecule or ion were modeled by AMOEBAbio09, a modern polarizable force field, and conventional non-polarizable AMBER99sb and CHARMM36 force fields. The resulting intermolecular interaction energies were compared with those calculated by ab initio quantum mechanics methods. Although the test is not sufficient to prove the reliability of the polarizable force field, the results at least validate its capability in modeling energetics of static configurations, which is one basic component in force field parameterization.

Description: A relatively new approach for wood protection against fungal decay is based on hydrophobization of wood and on lowering its moisture content. Water repellence of wood can be increased by polymerization of hydrophobic monomers in wood cell walls. It was found that Norway spruce wood after treatment with octadecyltrichlorosilane exhibited reduced water uptake by the wood cell walls, lowered water vapour sorption, and significantly increased dimensional stability of wood in terms of anti-swelling efficiency. Hydrophobicity and lower equilibrium moisture content were shown to cause increased resistance of the treated samples against brown-rot decay and molds.

Description: Recent emphasis on the pilot scale production of cellulosic nanomaterials has increased interest in the effective use of these materials as reinforcements for polymer composites. An important, enabling step to realizing the potential of cellulosic nanomaterials in their applications is the materials processing of CNC/polymer composites through multiple routes, i.e. melt, solution, and aqueous processing methods. Therefore, the objective of this research is to characterize the viscoelastic behavior of aqueous nanocomposite suspensions containing cellulose nanocrystals (CNCs) and a water-soluble polymer, poly(vinyl alcohol) (PVA). Specifically, small amplitude oscillatory shear measurements were performed on neat PVA solutions and CNC-loaded PVA suspensions. The experimental results indicated that the methods used in this study were able to produce high-quality nanocomposite suspensions at high CNC loadings, up to 67 wt% with respect to PVA. Additionally, the structure achieved in the nanocomposite suspensions was understood through component attributes and interactions. At CNC loadings near and less than the percolation threshold, a polymer mediated CNC network was present. At loadings well above the percolation threshold, a CNC network was present, indicated by limited molecular weight dependence of the storage modulus. Overall, these results provide increased fundamental understanding of CNC/PVA suspensions that can be leveraged to develop advanced aqueous processing methods for these materials.

Description: A method based on direct UV-detection was developed for the qualitative and quantitative determination of oligosaccharides simultaneously separated by capillary electrophoresis (CE). Reference compounds consisting of five xylo- three manno- and five cello-oligosaccharides were concurrently measured in a highly alkaline solution without derivatization. Sodium and potassium cations were used in the electrolyte solution to adjust the electrokinetic properties of the oligomers by controlling the mobility of charged species and to improve the resolution in baseline separation. The quantification range extended from 25 to 125 mg/L with linear correlation \(\hbox {R}^{2}=0.986{-}0.997\) for all analytes other than xylobiose and cellobiose, for which the range was 50–200 mg/L ( \(\hbox {R}^{2}=0.995\) ). The CE method developed was further applied to determine oligosaccharides from hot-water extracts of a bleached birch and pine kraft pulp, in which the oligosaccharides typically exist as complex mixtures.

Description: The axial modulus of the cellulose Iβ crystal is as high as 120–160 GPa. The importance of hydrogen bonds is often emphasized in this context, although intrinsic stiffness of the hydrogen bonds is relatively low. Here, hydrogen bond–covalent bond synergies are investigated quantitatively using molecular mechanics and molecular dynamics simulations for the so-called leverage effect, a model introduced recently in which strains for intra-molecular hydrogen bonds are higher than for the cellulose chain as a whole, thereby amplifying their contribution to the total stiffness. The present work also includes simulation of the hydrogen bonding band shifts in vibrational spectra during cellulose deformation, which are compared with FT-IR data. The leverage effect hypothesis was supported by the results, although the total contribution to cellulose stiffness is only 12 %. Hydrogen bonding is still critically important and would lower the modulus much more than 12 %, if “artificially” removed in the model. The reason is that intra-molecular hydrogen bonding preserves the crystal structure and directs axial deformation mechanisms towards higher energy deformation and high stiffness.

Description: For simply and accurately determining molecular weight of cellulose, an ionic liquid mixed with a co-solvent, 1-butyl-3-methylimidazolium acetate/dimethyl sulfoxide (BmimAc/DMSO) (1:1, w/w) was used and dissolved cellulose well at ambient temperature. During the dissolution process no degradation of cellulose was observed, and all the resultant cellulose/BmimAc/DMSO solutions were transparent and stable. These advantages make it as an ideal solvent system to build a new characteristic method of cellulose’s molecular weight by the measurement of the intrinsic viscosity [η], which is significantly better than the currently used solvent systems. [η] of solutions of nine cellulose samples was measured by using rheometer with cylinder fixture and Ubbelohde viscometer, respectively. The [η] values obtained by these two methods were well consistent. The degree of polymerization (DP) of these cellulose samples was determined by Copper (II) ethylenediamine method. Then the molecular weight and its distribution of representative samples were cross-checked by gel permeation chromatography for soluble derivatives of cellulose. As a result, a relationship DP = 134 [η] 1.2 was built, suitable for DPs in the range of 220–1400. The uncertainty of this relationship was estimated to be 5 %. This work provided a simple, accurate and reliable method for determining [η] and the molecular weight of cellulose.

Description: A sol-gel technique has been developed for the synthesis of a magnetite-silica-titania (Fe 3 O 4 -SiO 2 -TiO 2 ) tertiary nanocomposite with improved photocatalytic properties based on the use of inexpensive titania and silica precursors. The exceptional photocatalytic activity of the resulting materials was demonstrated by using them to photocatalyze the degradation of methylene blue solution. The best formulation achieved 98% methylene blue degradation. An interesting feature of the present work was the ability to magnetically separate and reuse the catalyst. The efficiency of the catalyst remained high during two reuses. The synthesized nanomaterials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, ultra-violet-visible spectroscopy, diffuse reflectance spectroscopy, and thermogravimetric analysis. XRD analysis revealed the formation of multicrystalline systems of cubic magnetite and anatase titania crystals. SEM and TEM characterization revealed well-developed and homo-geneously dispersed particles of size less than 15 nm. FTIR spectra confirmed the chemical interaction of titania and silica. It was further noticed that the optical properties of the prepared materials were dependent on the relative contents of their constituent metal oxides.

Description: Amphiphilic block copolymers (ABCs) assemble into a spherical nanoscopic supramolecular core/shell nanostructure termed a polymeric micelle that has been widely researched as an injectable nanocarrier for poorly water-soluble anticancer agents. The aim of this review article is to update progress in the field of drug delivery towards clinical trials, highlighting advances in polymeric micelles used for drug solubilization, reduced off-target toxicity and tumor targeting by the enhanced permeability and retention (EPR) effect. Polymeric micelles vary in stability in blood and drug release rate, and accordingly play different but key roles in drug delivery. For intravenous (IV) infusion, polymeric micelles that disassemble in blood and rapidly release poorly water-soluble anticancer agent such as paclitaxel have been used for drug solubilization, safety and the distinct possibility of toxicity reduction relative to existing solubilizing agents, e.g., Cremophor EL. Stable polymeric micelles are long-circulating in blood and reduce distribution to non-target tissue, lowering off-target toxicity. Further, they participate in the EPR effect in murine tumor models. In summary, polymeric micelles act as injectable nanocarriers for poorly water-soluble anticancer agents, achieving reduced toxicity and targeting tumors by the EPR effect.

Description: Poly(vinyl alcohol) (PVA) foams reinforced with cellulose nanocrystals (CNCs) were prepared with formaldehyde as a crosslinking agent. Two initial reaction times (10, 120 s) and the addition of CNCs (0–2 wt% based on total reaction suspension) were found to affect the foam density, water uptake, morphology and mechanical properties. A longer initial reaction time resulted in higher mechanical properties and density, due to the small pore size. The addition of CNCs induced a progressive decrease in the pore diameter and an increase in the foam density, as well as improved mechanical properties. With 1.5 wt% CNC content, the compressive strength of the PVA foams was significantly improved from 7 to 58 kPa for 10 s-initial reaction time and from 65 to 115 kPa for 120 s-initial reaction time. Results showed that the cross-linked PVA foams with CNC had promising properties for use in biomedical applications.

Description: A facile, fast, and economically viable method has been used to synthesize highly active copper (Cu) nanoparticles in chitosan (CH) coating layers over cellulose microfibers of filter paper (FP). FP was coated with 1 wt% CH solution (CH-FP) and kept in CuSO 4 aqueous solution to adsorb Cu 2+ ions. The Cu 2+ loaded CH-FP was treated with 0.1 M NaBH 4 aqueous solution to reduce the ions to Cu 0 nanoparticles. The Cu 0 loaded CH-FP (Cu/CH-FP) was characterized by FE-SEM, XRD, TGA and ATR-FTIR, which indicated the successful preparation of the Cu 0 nanoparticles by this method. The crystallinity of cellulose was not affected during the preparation process, which indicated that the Cu 0 nanoparticles were present in the amorphous thin CH layer around the cellulose microfibers of FP. The Cu/CH-FP was used in aqueous medium as an efficient catalyst for the reduction of toxic organic dyes. Our current study involved the degradation of methyl orange (MO) and Congo red (CR) dyes in the presence of NaBH 4 . The rate constants of 0.2683 and 0.1655 min −1 were observed for the MO and CR reductions. Besides good catalytic activity, the Cu/CH-FP catalyst strip could be easily recovered as compared to the other methods that are currently used. Recovery was accomplished by simply pulling the Cu/CH-FP strip from the reaction medium after completion of the reaction. The recovered Cu/CH-FP could be recycled several times provided that its exposure time to the air was minimal.

Description: The theory of mass transport in porous media is of fundamental importance for different applications such as food, paper packaging, textiles, and wood for building materials. In this study, a theoretical water vapor transport model has been developed for cellulose-based materials, such as paper and regenerated cellulose film. Pore diffusivities were determined from the dynamic moisture breakthrough experiments comprising a stack of paper sheets and regenerated cellulose films in a configuration similar to a packed adsorption column. Other mass transfer parameters were determined from transient moisture uptake rate measurements. The model incorporates pore and surface diffusion as a lump parameter into a variable effective diffusion coefficient. The mass transport, involving both pore and surface diffusions, is evaluated independently. The theoretical water vapor transmission rates (WVTRs) obtained from the model were compared with experimentally determined WVTRs measured under steady-state conditions. The theoretical model, based on intrinsic diffusion, stipulates higher WVTR values compared to the experimental results. However, the theoretical water vapor transfer rates agree well with the experimental results when external mass transfer resistance is incorporated in the model.

Description: Foamed materials are gaining an increased interest due to their good mechanical properties in relation to their low densities and an increased industrial demand can be expected. A few less attractive issues can however be associated with commodity foamed products. For instance the raw-material often originates from non-renewable, fossil-based, sources. Furthermore, degradation in nature is slow, therefor the disposed product is burned or end up in landfills. One possibility to reduce the impact on nature could be to produce foams from natural polymers such as starch or cellulose. In this study the possibility to produce foams from hydroxypropyl methylcellulose (HPMC) with water as blowing agent, by continuous extrusion, was investigated. A pre-study using a capillary viscometer, batch-extruder, was conducted to evaluate the foamability of HPMC. Due to promising results further experiments were conducted with a single-screw extruder. The goal was to find an adequate processing window for foaming. It was concluded that HPMC could successfully be foamed by continuous extrusion, although a careful tailoring of the processing parameters was required. Crucial parameters were here the temperature, pressure and residence time distribution in the extruder. Regions of the extruded foams were examined using optical and scanning electron microscopy and HPMC foams with a density in the range of that of fossil-based polymeric foams could be produced.

Description: Our NMR experiments show that chitin can dissolve well in aqueous KOH through a freeze-thawing process, and the dissolution power of the alkali solvent systems is in the order of KOH 〉 NaOH 〉 LiOH aqueous solution, which is totally contrary to that of cellulose in the alkali aqueous solution (i.e., LiOH 〉 NaOH ≫ KOH). In this work, we systematically study the dissolution process in KOH and KOH/urea aqueous solutions. Chitin has good solubility (solubility ~80 %) in 8.4–25 wt% KOH aqueous solution at −30 °C. The role of urea also has been investigated: unlike aqueous chitin-NaOH solutions, urea indeed enhances the solubility of chitin in KOH aqueous solutions, but the increased degree becomes unobtrusive with decreasing temperature and increasing dissolution time; the DA decline curves of chitin-KOH and chitin-KOH/urea aqueous solutions are nearly overlapping, indicating that the effect of the urea on the degree of acetylation of chitin in KOH aqueous solutions is small, similar to the NaOH/urea solvent.

Description: An aqueous suspension of cellulose nanocrystals (CNCs) was prepared by acidic hydrolysis of microcrystalline cellulose to be used as a nonsolvent in the fabrication of polyethersulfone (PES) membranes via the phase inversion method. The effect of CNC concentration on the membrane permeability, surface morphology and antifouling capability was probed. Also, the efficiency of adding nanocrystals to the nonsolvent for two different concentrations of PES dope solution was examined. The coagulation of PES in the presence of CNCs led to a more hydrophilic and smoother surface as well as higher bulk porosity. The thin skin layer and more porous membrane suggested higher water flux for CNC-treated membranes. Due to the hydrophilic nature of CNCs trapped in the membrane top layer, a superior antifouling ability was found for membranes precipitated in 0.1 wt% CNCs aqueous suspension. The concentration of the CNC suspension had a more significant influence on the permeability of membranes prepared by the dope solution with a low content of PES rather than highly concentrated one.

Description: Crease-resistant functionalization of cotton fabric was carried out using a combination of monofunctional carboxylic acid-based precursors, i.e. acrylic acid and dodecanoic acid. The reaction of precursors with cotton was carried out in situ using helium atmospheric pressure plasma at low frequency. After the treatment, a 40 % increase in CRA was achieved. The functional property developed after the treatment was durable against both solvent and soap washing. The effect of various parameters, such as the concentration of the precursor, helium flow rate, discharge power density and treatment time, on functionalization was investigated. Plasma was characterized using oscilloscope and optical emission spectroscopy. Modification of the chemical nature of the fabric surface was characterized by ATR-FTIR. The study of the surface morphology by FE-SEM revealed the formation of a uniform thin layer on individual fibers. The loss in tearing strength was limited to 28 %, while tensile strength remained unaffected. The plasma characteristics were correlated with crease-resistant functionalization.

Description: In this study, the effect of cellulose coating on dyeing and other properties of cotton fabric was investigated. Three different reactive dyes were used for dyeing coated cotton fabric. The effect of cellulose coating on the dyeing properties of cotton fabric was studied by determining the K / S values of coated substrate at different concentrations of cellulose and dye. The K / S value decreased by 40–60 % with increasing coating concentration of cellulose from 0 to 5 %. The results show that the stiffness was increased from 0.16 to 2.50 N/m by coating of cellulose on the surface of cotton fabric. The stiffness was permanent as confirmed by ten multiple washings. Mechanical properties remained excellent. X-ray diffraction analysis showed that the amount of cellulose II increased slightly after solvent treatment. Fastness properties of cellulose-coated cotton fabrics against rubbing, washing, and perspiration were good.

Description: The facile one-pot preparation of hydrophobic cellulose nanocrystals (CNCs) from wood pulpboard in an ionic liquid is reported in the present paper. This process employed a so-called amorphous cellulose solvent system capable of dissolving the majority of the amorphous regions in cellulose while maintaining the crystalline domains essentially intact, and consisting of tetrabutylammonium acetate with dimethylacetamide. These solvents were mixed at a mass ratio of 1:9 in conjunction with acetic anhydride to prepare CNCs via surface acetylation. The rod-like morphology and nanometer-scale dimensions of the resulting CNCs were ascertained by atomic force microscopy and transmission electron microscopy. Successful surface acetylation while maintaining an intact crystalline core was confirmed by Fourier transform infrared, 13 C CP/MAS NMR and X-ray photoelectron spectroscopy in addition to X-ray diffraction. Finally, the thermal stability and hydrophobic behavior of the hydrophobic CNCs were characterized using thermal gravimetric analysis and water contact-angle measurements, respectively.

Description: The impact of selected cellulose solvent systems based on the principal constituents tetrabutylammonium fluoride (TBAF), 1-ethyl-3-methyl-1 H -imidazolium-acetate, N -methylmorpholine- N -oxide, or calcium thiocyanate octahydrate (CTO) on the properties of cellulose II aerogels prepared from these solvent systems has been investigated as a means towards tailoring cellulose aerogel properties with respect to specific applications. Cotton linters were used as representative plant cellulose. Cellulose was coagulated from solutions with comparable cellulose content, and dried with supercritical carbon dioxide after solvent exchange. The resulting bulk aerogels were comprehensively morphologically and mechanically tested to relate structure and mechanical properties. Different solvent systems caused considerable differences in the properties of the bulk samples, such as internal surface area (nitrogen sorption), morphology, porosity (He pycnometry, thermoporosimetry), and mechanical stability (compression testing). The results of SAXS, WAXS, and solid-state 13 C NMR spectroscopy suggest that this is due to different mechanisms of cellulose self-assembling on the supramolecular and nanostructural level, respectively, as reflected by the broad ranges of cellulose crystallinity, fibril diameter, fractal dimension and skeletal density. Both solid state NMR and WAXS experiments confirmed the sole existence of the cellulose II allomorph for all aerogels, with crystallinity reaching a maximum of 46–50 % for CTO-derived aerogels. Generally, higher fibril diameter, degree of crystallinity, hence increased skeletal density were associated with good preservation of shape and dimension throughout conversion of lyogels to aerogels, and enhanced mechanical stability, but somewhat reduced specific surface area. Amorphous, yet highly rigid aerogels derived from TBAF/DMSO mixtures deviated from this trend, most likely due to their particular homogeneous and nanostructured morphology.

Description: In the present study hardwood fibre strength and fibre to fibre joint strength measurements using bleached, industrial eucalyptus kraft pulp have been performed. The device used for the measurements was a micro bond tester developed at Graz University of Technology. Results were compared to those obtained in previous studies dealing with both, hardwood and softwood. The mean force to break individual hardwood joints ( \(1.82\,\pm \,0.48\,\hbox {mN}\) ) was found to be 72 % smaller than that of unbleached softwood joints and is mainly governed by the bonded area of the joints. Furthermore, the optically bonded area (OBA) of hardwood fibre to fibre joints was investigated. OBA of hardwood joints is about 81 % smaller than those of softwood and the reduction is attributed to smaller width and lower collapsibility of the fibres. Compared to softwood, the force per unit OBA of hardwood is 1.72 times higher ( \(5.32\,\pm \,1.46\,\hbox {MPa}\) ). This difference is believed to be due to the well known size effect. Single fibre tensile testing resulted in a mean breaking load of \(38.81\,\pm \,16.31\,\hbox {mN}\) and show a 76 % reduction when compared to softwood. The reduction is attributed to the smaller cross sectional area and the effect of bleaching.

Description: A simple method for the preparation of polymer-cellulose nanocrystal (CNC) nanocomposite is shown to yield good dispersion of CNCs within a polylactide (PLA) matrix, which consequently resulted in the lowest rheological percolation threshold reported so far for polymer-CNC systems. The rheological behavior of the nanocomposites was determined in dynamic, transient, and steady-shear flow fields in the molten state. The complex viscosity and storage modulus of the nanocomposites increased markedly with CNC content, particularly at low frequencies; the samples were highly shear thinning and exhibited a transition from liquid- to solid-like behavior as the CNC concentration increased. Larger values for steady-state viscosity, yield stress, shear stress, and first normal stress difference were reported for the more concentrated nanocomposites. Also, pronounced overshoots in the transient start-up viscosity of the nanocomposites were observed. These results could be ascribed to the formation of an interconnected CNC network within the PLA matrix.

Description: A facile chemical precipitation approach is presented to fabricate flower-like zinc oxide (ZnO) nanorod clusters by using spherical cellulose nanocrystals (SCNs, with cellulose II crystal structure) as growth substrate. Field-emission scanning electron microscopy results showed that nanohybrids (A-100/11) with flower-like ZnO nanorod clusters could be formed under strongly alkaline (pH 11) conditions using suitable reaction time of 2 h and temperature of 100 °C, while rod-like nanohybrids could be obtained under weakly alkaline (pH 9.3 and 10.5) conditions or low temperature of 90 °C. A possible growth mechanism for flower-like ZnO on SCNs is discussed. Moreover, compared with commercial ZnO and rod-like nanohybrids, the flower-like A-100/11 nanohybrids showed better antibacterial activity against Streptococcus aureus and Escherichia coli , and excellent photocatalytic activity in presence of methylene blue as model dye.

Description: Uncontrolled growth of bacteria is always a major concern for various industries such as food, cosmetic and pharmaceutical industries. Taking this issue into account, a non-leaching antimicrobial surface was developed using cellulose nanofibers with a post grafting green method to mimic the antibacterial activity of chitosan. A series of experiments was designed for silylation of nanofibers with 3-aminopropyl trimethoxysilane, varying the initial concentration of silane and the solvent employed during the grafting. The results, validated by Fourier transform infrared spectroscopy, thermogravimetric analysis and elemental analysis, provided evidence of successful functionalization. Moreover, SEM–EDX indicated that a heterogeneous grafting occurred at the surface and cross section of the film. Strong antimicrobial activity against gram positive ( Bacillus subtilis and Staphylococcus aureus ) and gram negative ( Escherichia coli ) was recorded. In aqueous solution, the optimum results were obtained using grafting silane concentration of 50 g/L. The grafted CNF showed no change in the morphology or thermal stability, meanwhile a significant reduction in bacterial concentration of 1.3 logs for B. subtilis, 1.8 log for S. aureus and 3.8 logs for E. coli was observed. Regarding the solvent used during the grafting, acetone showed the reversibility of bonds between silanol groups and cellulose nanofibers or high self-condensation reaction which was depicted by the Si NMR and formation of zones of inhibition. Furthermore, water employed as grafting solvent depicted better grafting efficiency than acetone, 10.2 versus 6.4 % respectively, at the similar concentration with apparent lower grafting time.

Description: Acetylated cellulose powders with varying degree of substitution (DS) were prepared by reacting cellulose with acetic anhydride. The effect of DS on the hydrophobic properties of acetylated cellulose was examined based on contact angle and mechanical stability measurements. The surface energy of the acetylated cellulose decreases with increasing DS, and for DS of 0.39, the acetylated cellulose was able to encapsulate a water droplet to form a liquid marble. The corresponding cellulose acetate powder-over-water spreading coefficient was ca. 8.9. Increasing DS also improved the mechanical stability of the liquid marble. This study opens important perspectives for the precise control of DS of cellulose acetate for various practical applications in membranes, filters, scaffolds, and textiles.

Description: In this work we have developed low-cost, renewable and sustainable materials based on cellulose for electronic applications. The UV–Vis spectroscopy, water contact angle and differential scanning calorimetry results reveal a marked effect of absorbed water on the physical properties of cellulose nanopaper. Morphological observations reveal that the TEMPO oxidized cellulose-based foils were successfully covered by a 200-nm-thick copper layer by DC sputtering. The obtained low surface roughness, porosity and hydrophilicity of the nanopaper allow an efficient deposition of Cu on synthesized nanopaper. The thermal stability of cellulose nanopaper is markedly increased from 240 to 324 °C after Cu sputtering, results that are especially interesting for applications in which devices should withstand high temperatures. Dynamic mechanical analysis shows that the Cu-covered nanopaper maintains its mechanical stiffness up to ~180 °C. Finally, dielectric spectroscopy measurements reveal that developed Cu-coated nanopaper could emerge as a suitable bio-based material for radiofrequency applications. In this work we explore sputter coating as an alternative method to reduce the intrinsic hydrophilicity of synthesized nanopaper instead of including a polymer in the nanocellulose or functionalizing its surface chemically. The obtained findings highlight the potential application of transparent and mechanically robust cellulose nanopaper in the field of electronics and communication engineering.

Description: Sodium polyborate (SPB) has been employed with polyhexamethylene guanidine phosphate (PHMGP) to compose a nitrogen-phosphorus-boron intumescent coating on cotton fabric via a layer-by-layer (LBL) technique for obtaining excellent flame retardancy. The infrared spectra and atomic emission spectra indicate that the PHMGP-SPB multilayer grows gradually during the assembly process. Thermogravimetric analysis results show that the residue char of cotton is greatly enhanced after treatment with the LBL coating, which has a high char forming effect on cellulose during testing. The micro-calorimeter test finds that the assembly coating drastically decreases the peak heat release rate and total heat release of cotton fabric as a result of the catalytic charring effect. Cotton’s burning behavior is monitored by the flammability test, and the results show that ten bilayer (BL) coating with only 7.5 wt% can completely extinguish the flame on cotton samples. The oxygen index test reveals that the limiting oxygen index (LOI) of cotton samples is substantially increased by introducing the LBL coating. When the BL increases to 20, the LOI value reaches up to 41. The residual char after burning is analyzed by scanning electron microscope and infrared spectroscopy, and the results show the the LBL coating has an intumescent flame-retardant effect on cotton.

Description: A palladium catalyst supported on 2-aminopyridine functionalized cellulose was synthesized and fully characterized by inductively coupled plasma atomic emission spectroscopy, transmission electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectrometry. This catalyst can be applied in the Suzuki cross-coupling reaction of aryl halides with arylboronic acids in 50% ethanol to afford biaryls in good yields, and easily recycled by simple filtration after reaction without the loss of metal Pd.

Description: Along with advances in life science and clinical research, there has been an increasing interest in enrichment technologies for proteins with post-translational modifications. Here we report a new platform to enrich and detect phosphopeptides using the hybrid nanofibers synthesized from bacterial cellulose (BC). Hydrothermal reactions have successfully been employed to synthesize BC@mTiO 2 hybrid nanofibers. The morphology of the hybrid nanofibers has been characterized in detail. They are featured with tremendously increased specific surface areas and appropriate pore size for adsorption of phosphopeptides with high efficiency. The BC@mTiO 2 tips allow improving both the sensitivity and selectivity of mass spectrometry by nearly two orders of magnitude compared with the commercial tips. As a robust and highly cost-effective platform, our approach has provided a nanotechnology invention to enrich and detect phosphorylated proteins with important biomedical applications.

Description: The gas barrier and mechanical properties are crucial parameters for packaging materials, and they are highly correlated to the molecular interactions in the polymer matrix. To improve these properties of TEMPO-oxidized cellulose nanofibers (TOCNs) composite films, we studied the effect using hydroxypropyl guar (HPG) or carboxymethyl guar (CMG) in the preparation of TOCN composite films, which were made by following the solution-casting method. The subsequent film characterizations were carried out by UV–Vis spectra, scanning electron microscopy, oxygen and water vapor permeability measurements, tensile and thermogravimetric analyses. SEM results showed that CMG-based films had denser structures than their HPG counterparts. Moreover, the improved hydrogen bonding of the CMG-based films was partially responsible for the improved gas barrier performance, tensile strength and thermal stability. These results support the conclusion that CMG had advantages over HPG when used in the preparation of TOCNs packaging composite films.

Description: Interactions among cellulose, hemicellulose and pectins are important for plant cell wall assembly and properties and also for industrial applications of these polysaccharides. Therefore, binding of pectin and xyloglucan on microcrystalline cellulose was investigated in this experiment by adsorption isotherms, zeta potential and scanning electron microscopy (SEM). Analysis of three isotherm models (Langmuir, Freundlich and Fowler-Guggenheim isotherms) showed that the experimental adsorption isotherm was well described via the Fowler-Guggenheim model, which includes lateral interaction between the adsorbate. The adsorption isotherm and zeta potential measurement showed that at temperature 25 °C only xyloglucan adsorbed on the microcrystalline cellulose. In case of xyloglucan on cellulose, the equilibrium was reached in about 3–4 h, and the kinetics of adsorption were well described by the multiexponential equation. Analysis of the model suggests that two steps can be distinguished: diffusion and reconformation in an adsorbed layer. No adsorption of pectin was observed in this study. SEM study showed that xyloglucan may prevent cellulose from aggregation.

Description: Micro-fibrillar cellulose aqueous suspensions with different fiber lengths were prepared by mechanical refining of softwood pulp fiber suspensions at different specific refining energies. Effects of refining energy level, micro-fiber concentration and temperature on the rheological properties of these aqueous suspensions were studied. These microfibers form a three-dimensional network, which displays typical shear-thinning behavior with little thixotropic tendency, at concentrations as low as 0.5 wt%. A viscoelastic analysis showed that these micro-fibrillar cellulose suspensions at different concentrations (from 0.5 to 2 wt%) exhibit a viscoelastic gel-like behavior [G′ 〉 G″ over an extended range of frequencies (ω) and a weak dependency of G′ on ω] at 25 °C. The storage modulus, G′, at 1 rad/s increased strongly upon increasing concentration from 0.5 to 2 wt% following a power law with an exponent of 3.2. However, increasing the temperature decreases the storage modulus, G′, due to weakening or disruption of intermolecular interactions at elevated temperatures. The viscoelastic behavior changes to liquid-like, with G″ 〉 G′ at the investigated frequency range, for the suspensions at 85 °C.

Description: Great interests have arisen over the last decade in the development of hierarchically porous materials. The hierarchical structure enables materials to have maximum structural functions owing to enhanced accessibility and mass transport properties, leading to improved performances in various applications. Hierarchical porous materials are in high demand for applications in catalysis, adsorption, separation, energy and biochemistry. In the present review, recent advances in synthesis routes to hierarchically porous materials are reviewed together with their catalytic contributions.

Description: Building on the results of the green chemistry movement, the development of biodegradable strain sensors and OLEDs, produced from sustainable materials and solvents, is presented. The choice of solvents and substrate is discussed in the context of terms relevant to printing, namely solvent solubility parameters, surface wetting envelopes and surface roughness. A new method for producing biodegradable and flat substrates from a common and commercially available cellulose diacetate foil is presented. Challenges associated with working with biodegradable foils are presented and different techniques are discussed to ultimately overcome these challenges and produce functional devices. Lastly, many green solvents and several commercially available biodegradable foils are compared for consideration in future work.

Description: The effect of thermal pretreatment on the active sites and catalytic performances of PtSn/SiO 2 catalyst in acetic acid (AcOH) hydrogenation was investigated in this article. The catalysts were characterized by N 2 physical adsorption, X-ray diffraction, transmission electron microscopy, pyridine Fourier-transform infrared spectra, and H 2 -O 2 titration on its physicochemical properties. The results showed that Pt species were formed primarily in crystalline structure and no PtSn x alloy was observed. Meanwhile, with the increment of thermal pretreatment temperature, Pt dispersion showed a decreasing trend due to the aggregation of Pt particles. Simultaneously, the amount of Lewis acid sites was remarkably influenced by such thermal pretreatment owning to the consequent physicochemical property variation of Sn species. Interestingly, the catalytic activity showed the similar variation trend with that of Lewis acid sites, confirming the important roles of Lewis acid sites in AcOH hydrogenation. Moreover, a balancing effect between exposed Pt and Lewis acid sites was obtained, resulting in the superior catalytic performance in AcOH hydrogenation.

Description: After successful cationization of cellulose nanocrystals (CNCs) to produce pyridinium-grafted-CNCs, a variety of different cationic CNCs were prepared using a similar procedure, thus unlocking access to a wide variety of cationized cellulose nanocrystals through a simple one-pot reaction. In this study, cationic CNCs were prepared through the use of 4-(1-bromoethyl)benzoic acid or 4-bromomethylbenzoic acid, p -toluenesulfonyl chloride, CNCs, and two different amines, 1-methylimidazole and 4-dimethylaminopyridine. The amines acted as both the base catalyst for the esterification and the nucleophile to form the cationic charge. This method offers a versatile and straightforward route to prepare a variety of different cationic nanocrystals and therefore tailor their interaction with their environment.

Description: In this paper, a cellulase pretreatment was studied prior to the acid hydrolysis to decrease the total acid usage during the cellulose nano-crystals (CNC) preparation from a bleached softwood kraft pulp. Cellulase pretreatment facilitates the subsequent acid hydrolysis to produce CNC with similar quality to that of the control, but at a lower sulfuric acid concentration. The underline mechanism is that cellulase pretreatment led to the formation of more carbonyl groups which can be oxidized into carboxyl groups in the subsequent acid hydrolysis, furthermore, more hydroxyl groups are exposed, thus esterification into sulfonic groups can be enhanced. The results showed that with a cellulase dosage of 4.8 u/g (based on dry pulp) in the pretreatment stage, the sulfuric acid concentration can be decreased from 64 to 40 wt% without compromising the quality of resulting CNC particles. Other results from charge properties, Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) analyses also supported the conclusions.

Description: Cellulose-based fluorescent materials using Zinc sulphide (ZnS) quantum dot-decorated graphene were prepared by a one-step hydrothermal method. X-ray photoelectron spectroscopy analysis identified the chemical states of Zn, S, C, O, and N in the composite paper. Transmission electron microscopy showed that the graphite oxide was reduced to graphene sheets, and ZnS nanoparticles (〈10 nm) were deposited on the surface of these sheets. Scanning electron microscopy indicated that graphene sheets were attached to the surface of paper fibers, and the paper structure and morphology of the fibers were not observably damaged during the hydrothermal reaction. The cellulose-based composite had strong ultraviolet absorption in the range of 200–340 nm, and its main absorption peak was at approximately 296 nm. The band edge emission of photoluminescence spectrum of the composite occurred at 466 nm with an excitation wavelength of 320 nm. The laser scanning confocal microscope image of the composite exhibited an intense blue fluorescence under UV light at 405 nm.

Description: The surface grafting of cellulose nanocrystals (CNC) is a valuable tool to increase opportunities for their application. This work had several goals designed to improve CNC: reduction of hornification, increased re-dispersibility after CNC drying, and tuning of the surface graft to enhance the adsorption of particular molecules. To achieve this, the CNC surfaces were modified chemically with aromatic surface grafts using widely employed methods: the creation of urethane linkages, silylation and esterification. Even a low degree of grafting sufficed to increase water contact angles to as much as 96°. The analysis of water sorption isotherms showed that at high water activities, capillary condensation could be suppressed and hysteresis was decreased. This indicates that hornification was significantly suppressed. However, although the contact angles increased, the water sorption isotherms were changed only slightly because of reduced hysteresis. The grafts were not able to shield the surface from water vapour sorption. A comparison of the sorption isotherms of anisole and cyclohexane, sorbates with a similar surface area, showed that the sorption of anisole was three times higher than that of cyclohexane. The specific sorption of aromatic molecules was achieved and the most efficient methodology was the esterification of CNC with carboxylic acids containing a flexible linker between the aromatic moiety and ester bond.

Description: The use of ionic liquid solvents for the spinning of regenerated cellulose fibres has the potential to produce both technical and textile grade regenerated cellulose fibres. When spinning fibres, many parameters impact the material properties of the spun fibre. In this study, key wet spinning parameters have been investigated for the development of regenerated cellulose fibres from ionic liquid solutions. The coagulation and associated diffusion equilibrium were calculated for two imidazolium-based ILs, and it was found that the anion largely influenced the coagulation kinetics. This was likely due to the association between the anion of the IL and cellulose. The orientation of the polymer chains is known to influence the mechanical properties greatly; previously, hot stretching was used to orientate cellulose acetate. Here we investigated this influence on the mechanical properties of regenerated cellulose fibres by applying a post stretch at different stretch ratios.

Description: Nanofibrillated cellulose (NFC) is a type of nanomaterial based on renewable resources and produced by mechanical disintegration without chemicals. NFC is a potential reinforcing material with a high surface area and high aspect ratio, both of which increase reinforcement on the nanoscale. The raw materials used were unbleached and bleached bamboo organosolv pulp. Organosolv pulping is a cleaner process than other industrial methods (i.e. Kraft process), as it uses organic solvents during cooking and provides easy solvent recovery at the end of the process. The NFC was produced by treating unbleached and bleached bamboo organosolv pulps for 5, 10, 15 and 20 nanofibrillation cycles using the grinding method. Chemical, physical and mechanical tests were performed to determine the optimal condition for nanofibrillation. The delamination of the S2 layer of the fibers during nanofibrillation contributed to the partial removal of amorphous components (mainly lignin), which have low polarity and improved the adhesion of the fibers, particularly the unbleached cellulose. The transverse modulus of elasticity of the unbleached NFC was highest after 10 nanofibrillation cycles. Further treatment cycles decreased the modulus due to the mechanical degradation of the fibers. The unbleached NFC produced by 10 cycles have a greater transverse modulus of elasticity, the crystallite size showed increase with the nanofibrillation, and after 5 nanofibrillation cycles, no differences are observed in the morphology of the fibers.

Description: Many tonnes of agricultural wastes are generated annually, which contains a relatively high amount of cellulose; banana pseudo-stem is one waste type that is a promising material for nanocellulose production. This research characterised nanocellulose from inner and outer layers of banana pseudo-stem as a preliminary research strategy for designing biodegradable packaging material from banana pseudo-stem nanocellulose. Nanocellulose was successfully prepared through TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl)-mediated oxidation. The extracted nanocellulose from both the inner and outer layers had observed widths of approximately 7–35 nm and long fibrillated fibre. They had high negative zeta potential (lower than −33.6) that provided good colloidal stability. The purity of the nanocellulose was high as demonstrated by 13 C solid-state NMR and Fourier transform infrared spectroscopy. Nanocellulose from both layers was significantly more crystalline than the raw materials. Thermal stability of nanocellulose sourced from inner and outer layers was relatively similar, with degradation temperature of approximately 220 °C, which was slightly lower than the degradation temperature of its native form (232 °C for inner layer and 261 °C for outer layer).

Description: In this work lignocellulose biomass liquefaction was used to produce biopolyols suitable for the manufacturing of rigid polyurethane foams. In order to better evaluate the mechanism of the process, pure cellulose was applied as a raw material. The effect of time and temperature on the effectiveness of liquefaction and the parameters of resulting biopolyols were characterized. The prepared materials were analyzed in terms of their chemical structure, rheology, thermal and oxidative stability, and basic physical and mechanical properties that are important from the point of view of polyurethane manufacturing. The optimal parameters for the biopolyol production with a 94 % yield were achieved at 150 °C for a 6-h reaction duration. The obtained polyols were characterized by the hydroxyl number of 643 mg KOH/g and enhanced thermal and oxidative stability compared to the polyols obtained at lower temperatures, which is associated with the altered mechanism of liquefaction. The results of rheological tests, analyzed with the use of Ostwald-de Waele and Herschel Bulkley models, revealed that the prepared biopolyols can be classified as pseudoplastic fluids with the viscosity values similar to those of commercially available products. Rigid foams obtained via partial substitution of petrochemical polyol with prepared bio-based one were characterized by slightly increased apparent density and average cell size comparing to unmodified materials. The best mechanical performance was observed for the sample containing 35 wt% of biopolyol in the polyol mixture, which indicates a synergistic effect between the applied polyols. The applied modification delayed thermal degradation of foams due to changes in thermal decomposition process. In conclusion, the presented work confirms that lignocellulose biomass liquefaction can be successfully applied as a manufacturing method of polyols later used in the production of polyurethanes.

Description: Polysaccharides are finding an increasing number of applications in medical and pharmaceutical fields thanks to their biodegradability, biocompatibility, and in some cases bioactivity. Two approaches were applied to use hemicelluloses as crosslinkers to tune the structural and mechanical properties of nanofibrillated cellulose (NFC) hydrogel scaffolds, and thus to investigate the effect of these properties on the cellular behavior during wound healing application. Different types of hemicellulose (galactoglucomannan (GGM), xyloglucan (XG), and xylan) were introduced into the NFC network via pre-sorption (Method I) and in situ adsorption (Method II) to reinforce the NFC hydrogels. The charge density of the NFC, the incorporated hemicellulose type and amount, and the swelling time of the hydrogels were found to affect the pore structure, the mechanical strength, and thus the cells’ growth on the composite hydrogel scaffolds. The XG showed the highest adsorption capacity on the NFC, the highest reinforcement effect, and facilitated/promoted cell growth. The pre-sorbed XG in the low-charged NFC network with a lower weight ratio (NFC/XG-90:10) showed the highest efficacy in supporting the growth and proliferation of fibroblast cells (NIH 3T3). These all-polysaccharide composite hydrogels may work as promising scaffolds in wound healing applications to provide supporting networks and to promote cells adhesion, growth, and proliferation.

Description: For the first time, a multiplanar photonic crystal structure has been obtained using cellulose as a structural material. This all-polymer system, made of cellulose, polyvinyl alcohol and poly( N -vinylcarbazole) is a ternary planar photonic crystal composed by 7 repeated trilayers produced by spin coating. Trimethylsilyl cellulose is used as a precursor to be converted to cellulose. Transverse Transmission Electron Microscopy analysis of our systems confirms the multilayered structure whose optical response can be theoretically accounted for. Preliminary results on the response of the photonic crystal to water vapors envisage the use of this system for humidity optical sensing.

Description: The gel point is the lowest solids content at which a fibre suspension forms a continuously connected network and is related to the fibre aspect ratio. In this paper we firstly investigated the conditions required to accurately measure a gel point using sedimentation. We found that very heavily treated cellulose nanofibres can produce anomalous sedimentation data, due to the electrostatic repulsion from fibre surface charges dominating the gravity driven sedimentation. Screening the anionic surface charges by adding high levels of Na + or Ca 2+ ions reduced the electrostatic interactions between the fibres and allowed them to settle normally. Gel point measurement was then used to probe the development of nanofibre quality with increasing energy input for three different feedstocks: eucalypt kraft pulp, commercial microfibrillated cellulose and de-lignified, bleached spinifex pulp. By combining the data of the aspect ratio and average diameter, determined from SEM and TEM, we were able to compare the differences in feedstock processability. The aspect ratio of all three feedstocks increased with increasing homogenisation energy, showing that the fibre delamination dominated over fibre shortening. The slope of the aspect ratio versus energy consumption showed the ease of processing of each sample. The spinifex fibres had the fastest rate of aspect ratio increase and therefore were the most processable. Gel point is an excellent tool to track quality development of nanocellulose through processing and to compare the potential of different feedstocks for nanocellulose production.

Description: Bacterial cellulose (BC) has great potential for use as a tissue scaffold due to its unique structure and properties including high tensile strength and good biocompatibility. However, poor biodegradability of BC in the human body may be a key disadvantage limiting its application in the field. In this paper, we developed a simple absorption method to prepare biodegradable cellulase/BC materials. The morphology, structure, degradation ratio and mechanical properties during the degradation process were characterized and investigated. In vitro studies reveal that the BC material degraded gradually in simulated body fluid within 24 weeks and the degradation rate could be adjusted by modulating the cellulase content. The mechanical properties indicate the cellulase/BC material could maintain tensile strength for as long as 24 days during the degradation process. Muscle-derived cells were seeded on the cellulase/BC material to evaluate the cytotoxicity, using LIVE/DEAD ® viability/cytotoxicity assay and H&E staining. In vivo biocompatibility was evaluated by subcutaneous implantation using a dog model for 1, 2, 3 and 4 weeks. These results demonstrate that the cellulase/BC material had good in vitro and in vivo biocompatibility.

Description: Recently, the rapidly expanding use of nanocellulose has been focused on abundant, light-weight, sustainable, biodegradable, and potential materials. This paper presents a summary of the findings of an exploratory study conducted to investigate the facile processing of nanocellulose from a kenaf core using electron beam irradiation. In this study, nanocellulose was produced by first isolating cellulose from a kenaf core, and then conducting electron beam irradiation and acid hydrolysis followed by a TEM analysis to confirm the form of the nanocellulose fibers. As the dose of electron beam irradiation increased, the crystallinity, molecular weight, polydispersity, and decomposition temperature of cellulose decreased. Such results influenced the size distribution and yield in acid hydrolysis; as the absorbed dose and acid hydrolysis reaction time increased, the yield of nanocellulose decreased while the size distribution became narrower.

Description: Hybrid materials based on cellulose nanofibrils (CNF) and gold nanoparticles (AuNPs) are synthesized and novel routes to couple AuNPs on the CNF surface are introduced. Quaternary ammonium, azido, alkyne and amino functional groups were used for the attachment of metal particles on the corresponding functionalized CNF (EPTMAC-CNF, Azido-CNF, Propargyl-CNF, Amino-CNF, respectively). The CNF-based supports were characterized by Fourier transform infrared spectroscopy and the surface charge was assessed by ζ-potential measurements. The AuNPs were attached on the functionalized CNF surface via either electrostatic interactions or click reactions. The obtained CNF/AuNPs hybrid materials were characterized using transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectrometry. The obtained Bio-inorganic hybrid materials are potentially suitable for surface-enhanced Raman scattering, chemosensing and catalytic applications.

Description: Cationic hyperbranched polyethylenimine (hPEI) was covalently linked onto the backbone of cellulose molecules via forming Schiff base structure between the amino groups of hPEI and the aldehyde groups on the chemically oxidized cellulose surface. The functionalized hPEI-CE possessed available active sites, and its adsorption behavior to anionic dye congo red (CR) and cationic basic yellow 28 (BY28) in aqueous solution was investigated. The hPEI-CE interacted with the two dyes, exhibiting sharp response to solution pH and ionic strength. The adsorption process was well dominated by the pseudo-second-order kinetic model. And the hPEI-CE following the Langmuir isotherm model, had a maximum adsorption capacity of 2100 mg g −1 for CR and 1860 mg g −1 for BY28, respectively. Further, the adsorption performance of six dyes onto the hPEI-CE was studied, which showed high adsorption capacities for CR, BY28, brilliant blue 133 (BB133), and reactive red, but very low adsorption for cationic bright yellow 7GL (7GL) and eosin Y (EY). The different adsorption performances for different dyes indicated the selective adsorption of the hPEI-CE for dyes owing to their different distribution coefficient ( K ) defining as the partition of dyes between hPEI-CE and water. Based on the unique selective adsorption, the mixtures of dyes, such as BB133-CR, BB133-BY28, BB133-7GL, and CR-7GL, were separated successfully using hPEI-CE.

Description: A whole paper electro-biosensor detection platform for detecting glucose is reported. Glucose oxidase was immobilized on paper-based screen-printed carbon electrodes. The developed biosensor has an excellent electrochemical characteristic and high heterogeneous electron transfer rate constant (k s  = 4.23 × 10 −4 ). This new detection platform exhibited good amperometric responses toward glucose, with a wide linear range up to 10 mM with R 2 is 0.9973 and the sensitivity is 2.07 μA mM −1 . The parallel measurements of glucose by different biosensors had a low relative standard deviation of 4.26 % and demonstrated it had good reproducibility. In the interference studies, there was no significant difference with ascorbic acid or uric acid. For stability, it retained 93.9 % of its initial response after a storage period of 31 days in 4 °C. Besides, the Parkes error grid analysis was indicated that paper-based electrochemical biosensor has a good accuracy on the glucose detection.

Description: A new process for preparing thin cellulose nanofibril (CNF) filaments (thickness of 16 µm) was investigated by utilizing the dry spinning approach. In the process, CNF hydrogel was extruded through a fine nozzle onto an adhesion controlled capstan (drum) with low friction (slippery surface) at a speed of up to 11 m/s. The utilized capstan enables excellent line speed control when the slippery surface is applied, and prevents drying shrinkage of the spun filaments. The mechanical properties of prepared filaments can be optimized with the stretch ratio, the ratio of the speed of the drum surface, and the CNF jet flow. The developed method allows for manufacturing thin CNF filaments with an elevated spinning rate in a more controlled manner.

Description: As skin defects cannot regenerate by themselves, tissue engineering through tissue-mimicking scaffolds holds promise for treating such defects. In this study, cellulose acetate (CA)-based three-dimensional scaffolds were produced using the wet-electrospinning technique, and the influence of concentrations on the properties of the wet-electrospun scaffolds was investigated for the first time. CA with concentrations of 4, 5, 6, 7, 8, 9, 10, 12 and 14 % (w/v) were dissolved in acetone to fabricate the scaffolds. Wet electrospinning was carried out under an applied voltage of 15 kV and a tip-to-bath distance of 10 cm into the aqueous solution of sodium hydroxide (NaOH) (pH ~13) as a coagulation bath. The specimens with concentrations of 4–7 % (w/v) just produced droplets. The concentration of 8 % (w/v) produced beaded fibers, and the fibers of 9, 10, 12 and 14 % (w/v) were almost oriented in a random, dispersive manner and formed a non-woven structure morphology under scanning electron microscope (SEM) observation. The porosity measurement via the liquid displacement method showed that all scaffolds could not meet the accepted ideal porosity percentage of above 80 %, and the highest recorded porosity percentage was 69.5 % for the 12 % (w/v) scaffold. The contact angle measurement data displayed the high hydrophobicity of all scaffolds, which was expected because of the hydrophobic nature of CA. In vitro L929 mouse fibroblast cell culture demonstrated that all scaffolds presented a non-toxic environment and enhanced cell proliferation and attachment.

Description: With the depletion of crude oil reserves, the ever-increasing global energy consumption encourages the efforts to find alternative renewable sources for production of biofuels and value-added chemicals. The conversions of lignocellulosic biomass into biofuels and commodity chemicals via the biotechnological pathway have been the recent trend. Specifically, these products can be obtained through fermentation of reducing sugars, which are the main but basic derivatives from the biomass. In order to overcome the recalcitrant structure of the biomass for effective reducing sugar recovery, a pretreatment stage is normally required. Currently, one of the most novel forms of biomass pretreatment is using energy irradiation methods such as electron beam, gamma ray, pulsed electrical field, microwave and ultrasound. In general, these technologies are often used together with other more conventional chemical and/or biological pretreatment techniques for enhancing sugar recovery. Nevertheless, energy irradiation offers significant improvement in terms of possible cost reduction opportunities and reduced toxicity. Hence, this review highlights the recent studies of using energy irradiation for pretreating biomass as well as the industrial applications of reducing sugars in biotechnological, chemical and fuel sectors. In short, more research needs to be done at the scientific, engineering and economic levels to make energy irradiation one of the front runners in the field of biomass pretreatment.

Description: Recent findings indicate there is only a small window of sulfuric acid concentration (60–65 %) and temperature (45–65 °C) which allows efficient extraction of cellulose nanocrystals in significant quantities from bleached chemical pulp. In the present report, we develop a systematic explanation for how hydrolysis temperature, at a specific acid concentration, governs CNC surface properties. We demonstrate that CNCs with different suspension viscosity, stability in electrolyte-containing solutions, and optical properties can be produced, based on the presence or not of a precipitated oligosaccharide layer (OSL) on the surface of the nanocrystals. At hydrolysis temperatures below 65 °C, the degree of polymerization (DP) distribution of cellulose chains in CNC samples exhibits a bimodal distribution, indicating an accumulation of oligosaccharides on the CNC surface which increases as the hydrolysis temperature is decreased. At low hydrolysis temperature (45 °C), the oligosaccharides dissolved in the strong acid phase have a DP between 7 and 20 and precipitate onto CNCs when the reaction is quenched by diluting with water. As the temperature of hydrolysis is increased (50–60 °C), the dissolved oligosaccharides are hydrolyzed faster and their DP decreases such that they remain soluble after quenching. At 65 °C, no precipitated oligosaccharides can be detected on the CNC surface. Based on these results, we propose possible explanations to account for the effects of the OSL on the CNC suspension viscosity and stability and on optical properties of CNC films.

Description: As a biodegradable, inexpensive and universally accessible material, paper is used widely in many applications, including packaging, office supplies and household products. However, the hydrophilic and oleophilic nature of paper often limits its use in applications that involve direct contact with liquids. The main purpose of this study was to create highly amphiphobic paper for products such as low cost medical testing strips, liquid packaging, and breathable and disposable medical apparel. A three-step process was developed to create paper with contact angles greater than 150° for water and motor oil, and greater than 140° for n -hexadecane. First, a commercially available debonding agent was used to manipulate the dimensions of the fiber network through efficient fines removal and modification of inter-fiber hydrogen bonding. Then an oxygen plasma was used to create nano-scale roughness on the micrometer-sized fibers and to remove residual fines that were blocking the inter-fiber pores. Finally, the paper was immersed in a fluorosilane solution to obtain a thin, low surface energy coating. XPS, SEM, mercury porosimetry and profilometry were used to evaluate changes in the fiber network after each step. This study marks the first report that uses debonder agents specifically to modify the anti-wetting properties of paper substrates by controlling the topology of the fiber network. The processes used in this procedure are simple, cost effective and amenable to scale-up.

Description: To understand the correlation between structural feature and removal capability, a series of cellulose-based bioadsorbents with controlled pore size and functional group contents were designed and synthesized by grafting acrylic acid and acrylamide onto cellulose backbone chains. The adsorption behavior of these bioadsorbents to three metal ions [Cr(III), Cu(II) and Co(II)] in aqueous solution was investigated. The correlation between structural feature of cellulose-based bioadsorbents and their removal capability was studied in detail. The obtained cellulose-based bioadsorbents interacted with different metal ions, exhibiting highly effective ion removal from aqueous solution at a wide pH range of 3.0–5.0. The maximum adsorption of Cr(III), Cu(II) and Co(II) was determined as 220.64, 213.49 and 137.55 mg/g, respectively, when the cellulose-based bioadsorbents were treated by 2000 mg/L metal solution at pH 3.0 for 14 h. Moreover, the competitive adsorption showed that cellulose-based bioadsorbents had higher adsorption selectivity for Cr(III) (54.72 mg/g) with the coexistence of Cu(II) and Co(II). The adsorption mechanisms were interpreted considering the functional groups of bioadsorbent, ion characteristics, and varitation of solution acidity. The higher adsorption of Cr(III) could be ascribed to the stronger attraction to the lone pair of electrons both in oxygen and nitrogen atom to form more stable complexes, while only carboxyl/carbonyl groups participated in the adsorption of Cu(II) and Co(II). These results are important because they provide not only a approach to structure-controlled adsorbent for pollutant removal, but also interesting information concerning the adsorption capability of these structures based on pore size and surface functional groups.

Description: Dissolution of cellulose is the key challenge in its applications. It has been discovered that spruce cellulose with high molecular weight (4.10 × 10 5  g mol −1 ) can be dissolved in 64 wt% H 2 SO 4 aqueous solution at low temperature within 2 min, and the cellulose concentration in solution can reach as high as 5 % (w/v). FT-IR spectra and XRD spectra proved that it is a direct solvent for cellulose rather than a derivative aqueous solution system. The cold H 2 SO 4 aqueous solution broke the hydrogen bonds among cellulose molecules and the low temperature dramatically slowed down the hydrolysis, which led to the dissolution of cellulose. The resultant cellulose solution was relatively stable, and the molecular weight of cellulose only slightly decreased after storage at −20 °C for 1 h. Due to the high molecular weight of cellulose, cellulose solution could form regenerated films with good mechanical properties and transparency at low concentration (2 % w/v). This work has not only provided the new evidence of cellulose dissolution which facilitated the development of cellulose solvent, but also suggested a convenient way to directly transfer cellulose with high molecular weight into materials without structure modifications.

Description: Molecular self-diffusion coefficients were measured in solutions of microcrystalline cellulose (MCC) and dissolving pulp, in 40 wt% aqueous tetrabutylammonium hydroxide (TBAH), using pulsed field gradient stimulated echo NMR. From the cellulose diffusion coefficients, a weight averaged radius of hydration 〈R h 〉 w  = 6.1 nm for MCC and 〈R h 〉 w  = 15 nm for pulp were obtained. Water and TBA + ions show a significantly different dependence on the cellulose concentration, revealing different molecular interactions with the polymer. Water-cellulose are essentially excluded volume. TBA + ions, on the other hand, bind to cellulose with approximately 1.2 TBA + ions per glucose unit.

Description: In this study, the effect of alkaline pretreatment on preparation of regenerated lignocellulose fibers from bamboo stem was studied in detail. Prior to being dissolved in [Emim]OAc, bamboo stems were ground and treated with different concentrations of sodium hydroxide solutions. The obtained spinning dopes were then extruded into water coagulation bath and regenerated to composite fibers. The properties of the raw materials, spinning dopes, and regenerated fibers were investigated. Results showed that alkaline pretreatment could break the rigid structure of lignocelluloses by removing part of hemicelluloses and lignin as well as changing the polymorphous lattice and C r I of cellulose. The increased specific surface area of raw materials enhanced the accessibility of solvent, promoted the swelling process and shortened the dissolution time. The viscosity of the spinning dopes and the strength of the regenerated fiber reached the maximum value when the bamboo powder was treated with 20 wt% sodium hydroxide at 60 °C for 4 h. In addition, the fibers prepared from the alkali-treated raw materials showed round cross-section and wrinkled surface. Therefore, the properties of the regenerated lignocellulose fibers could be improved by employing an appropriate alkali pretreatment of raw materials.

Description: Tracking the changes of cellulose crystallites upon thermo-hygro-mechanical treatment is essential to understand the response of wood cell walls to steam and compression. In this paper the influence of Compression combined with Steam (CS) treatment on wood cellulose crystallites and pores structure of Chinese fir ( Cunninghamia lanceolata ) was studied under different steaming temperatures and compression ratios. Small-angle X-ray scattering and wide-angle X-ray scattering were used to investigate the changes of cellulose crystallites dimension, aspect ratio, fibril diameter distribution, non-crystalline fraction, the number of chains in each microfibril, as well as the fractal dimension and size of pores in response to CS treatment conditions. Results indicate that the crystallinity increased due to CS treatment, but did not show alteration with varying CS treatment conditions, i.e. seemed nearly unaffected by higher temperatures or compression ratio, both for earlywood and latewood. The cellulose crystallite diameter depended on processing parameters: it increased with increasing treatment temperature. No considerable differences were found for earlywood and latewood. We interpret our findings as a rearrangement of adjacent cellulose chains towards higher crystalline perfection attributing to the increase in crystallinity. The same effect allows a larger coherence length of crystalline order and therefore features an increasing cross-sectional dimension. In general we can state that the CS treatment leads to higher crystallinity and more perfectly arranged cellulose crystals, while it does not greatly affect the microfibril diameter but rather the amorphous regions of the microfibrils and the surrounding hemicellulose and lignin.

Description: Bacterial cellulose (BC) is a versatile biopolymer with better material properties, such as purity, high degree of porosity, relative high permeability to liquid and gases, high water-uptake capacity, tensile strength and ultrafine network. This review explores the applications of BC and its hydrogels in the fields of food, cosmetics and drug delivery. Applications of BC in foods are ranging from traditional dessert, low cholesterol diet, vegetarian meat, and as food additive and dietary aid to novel applications, such as immobilization of enzymes and cells. Applications in cosmetics include facial mask, facial scrub, personal cleansing formulations and contact lenses. BC for controlled drug delivery, transdermal drug delivery, dental drug delivery, protein delivery, tissue engineering drug delivery, macromolecular prodrug delivery and molecularly imprinted polymer based enantioselective drug delivery are also discussed in this review. The applications of BC in food and cosmetics provide the basis for BC-based functional foods, nutraceuticals, cosmeceuticals and medicated cosmetics. On the basis of current studies, the BC-based drug delivery could be further fine-tuned to get more sophisticated control on stimuli-responsive drug release. Along with the currently available literature, further experiments are required to obtain a blueprint of drug in vivo performance, bioavailability and in vitro–in vivo correlation.

Description: Room-temperature sodium-based batteries have the potential for meeting large-scale grid energy storage needs. Inspired by the advancement of the design and building of electrode materials in lithium ion batteries, improved nano-architectured electrodes can be created for sodium-ion batteries, allowing increased electron transport kinetics and conductivities. Here, nanocomposites with 3D porous structures are reported as a high-capacity anode material for sodium-ion batteries by using an easy, low-cost and environmentally friendly synthesis of pyrolyzed bacterial celluloses (PBCs). Bacterial celluloses (BCs) produced by the Gluconacetobacter xylinus strain are pyrolyzed at 500, 750 and 1000 °C, resulting 50, 130 and 110 mAh g −1 capacities over 80 numbers of cycles, respectively, in the presence of the binary ethylene carbonate–propylene carbonate mixture. In order to increase the cell performances, in situ coated SnO 2 nanoparticles with bacterial cellulose (SnO 2 @PBC) are produced by addition as synthesized 5-nm-sized SnO 2 nanoparticles into the BC growth medium together with the G. xylinus strain. Following the pyrolysis at 500 °C, the SnO 2 @PBC composite is better able to handle the accommodation of the dramatic volume change of the incorporated SnO 2 nanoparticles because of the interaction of oxygen-containing moieties of bacterial cellulose nanofibrils with the SnO 2 nanoparticles during cellulose production. The resulting SnO 2 @PBC composite presents highly stable capacity retention of around 400 mAh g −1 capacities at C/10 current density over 50 numbers of cycles.

Description: A green and efficient adsorbent for adsorption of palladium ions was prepared from 2,3-dialdehyde cellulose (DAC) originating from nanocellulose from the green algae Cladophora . The DAC was functionalized with cysteine via reductive amination in a convenient one-pot procedure to provide the adsorbent. The adsorption properties for adsorbing palladium(II) ions, including capacity, adsorption isotherm and kinetics, were studied. The successful reductive amination of cysteine with 2,3-dialdehyde cellulose was confirmed by FT-IR, elemental analysis and XPS. The adsorbent was characterized by SEM, XRD, gas adsorption and TGA. The adsorbent had a high adsorption capacity (130 mg palladium per gram adsorbent) and enabled fast adsorption of palladium(II) ions from solution (80 % of maximum capacity reached in 2 h). Adsorbent materials suitable for both filters (fibrous) and column matrixes (spherical particles) could be obtained in an efficient manner by controlling the degree of oxidation while producing the DAC material.

Description: Different contents of bonded cellulose were dispersed in a matrix of castor-oil-based polyurethane to produce composites with high susceptibility to fungal attack. We chose to bond the cellulose filler with free diisocyanate, to increase the crosslinking density. Measurements indicated physical and chemical interactions between the polyurethane matrix and cellulose filler. The cellulose network significantly enhanced the interfacial adhesion and thus improved the thermal stability and Young’s modulus of the composites. The influences of the amount of cellulose on the surface chemical structure, surface morphology, and mechanical properties after fungal attack were also investigated. The tensile strength and elongation at break of these composites substantially decreased after exposure to fungus. These composites with high content of renewable raw materials present an optimal balance of physical properties and biodegradability, with potential applications as ecofriendly biomaterials.

Description: Polycaprolactone (PCL) was grafted to TEMPO-oxidized nanocellulose (TONCs) through a classical ring-opening polymerization reaction mediated by the surface TONC hydroxyl and carboxyl groups. The PCL increased the thermal stability and hydrophobicity without compromising the crystallinity. When TONCs and PCL-grafted TONCs (PTONC) were compared with respect to their perfusion within a segmented polyurethane matrix (CLPU), PTONC dispersed far better as evidenced by increased storage modulus and Young’s modulus. The mechanical strength of the PTONC nanocomposites was nearly that of unmodified TONCs while at a low content (〈3 wt%). Furthermore, PTONC in CLPU promoted micro-phase separation of the matrix leading to a smaller decrease in loss factor and elongation at break for the nanocomposites, highly superior to unmodified TONCs. Thus, PTONC as a reinforcement agent enhanced the mechanical properties and ductility of CLPU.

Description: It is well documented that the enzymatic hydrolysis of cellulose follows a reaction pattern where an initial phase of relatively high activity is followed by a gradual slow-down over the entire course of the reaction. This phenomenon is not readily explained by conventional factors like substrate depletion, product inhibition or enzyme instability. It has been suggested that the underlying reason for the loss of enzyme activity is connected to the heterogeneous structure of cellulose, but so far attempts to establish quantitative measures of such a correlation remain speculative. Here, we have carried out an extensive microscopy study of Avicel particles during extended hydrolysis with Hypocrea jecorina cellobiohydrolase 1 (CBH1) and endoglucanase 1 and 3 (EG1 and EG3) alone and in mixtures. We have used differential interference contrast microscopy and transmission electron microscopy to observe and quantify structural features at μm and nm resolution, respectively. We implemented a semi-automatic image analysis protocol, which allowed us to analyze almost 3000 individual micrographs comprising a total of more than 300,000 particles. From this analysis we estimated the temporal development of the accessible surface area throughout the reaction. We found that the number of particles and their size as well as the surface roughness contributed to surface area, and that within the investigated degree of conversion (〈30 %) this measure correlated linearly with the rate of reaction. Based on this observation we argue that cellulose structure, specifically surface area and roughness, plays a major role in the ubiquitous rate loss observed for cellulases.