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This study focused on the assessment of thermal safety associated with the synthesis of N-methylmorpholine-N-oxide (NMMO), a reaction known to be hazardous. First, a reaction calorimeter (SIMULAR) was used to investigate the exothermic behavior of the reaction in the semi-batch operation. The overall heat of the synthesis of 121.69 kJ mol−1 (based on the molar of N-methylmorpholine) and the maximum temperature of the synthesis reaction (MTSR) of 352.71 K under uncontrolled conditions were derived from calorimetric data and high-performance liquid chromatography results. Second, the thermal decomposition of H2O2/NMMO and NMMO under non-isothermal and adiabatic conditions and the possibility of secondary decomposition under runaway conditions were analyzed by differential scanning calorimetry and accelerating rate calorimetry to calculate the time to maximum rate (TMRad) and the temperature as TMRad is 24 h. The heat of decomposition of NMMO ranged from 314.23 to 416.23 J g−1. The activation energy (Ea), calculated using the kinetics method under non-isothermal conditions, was 40–89 kJ mol−1, which was lower than that derived under adiabatic conditions. Furthermore, the TD24 of H2O2/NMMO was lower than that of NMMO owing to the coupling effect. Finally, the risk assessment of thermal runaway was conducted on the basis of the Stoessel criticality diagram. The results indicated that the synthesis of NMMO has a class 2 risk level. Although the risk of the synthetic reaction is low, there are still hidden dangers such as thermal hazards during the NMMO synthesis in the presence of H2O2.

Several literature reports describe the role of aqueous solutions of N-methylmorpholine-N-oxide monohydrate (NMMO) as a suitable medium for the generation of transition metal (nano)particles in or on cellulosic materials and further elaborate its role as a co-reactant of the transition metal salts that are reduced to the elemental metal. However, this would assign NMMO the role of a reductant, which is in contradiction of its obvious oxidative nature. In the present study, the exemplary cases of silver, gold, and platinum salts as the precursors of the respective metal (nano)particles in aqueous NMMO/cellulose mixtures were investigated. Naturally, NMMO did not act as a reducing agent in any case—this role was taken over by the frequently used NMMO stabilizer propyl gallate, or by cellulose itself, into which carbonyl and carboxyl groups were introduced. Also, hypochlorite—produced intermediately from chloride ions and subsequently undergoing disproportionation into chloride and chlorate—or transient N-methylene(morpholinium) ions generated from NMMO, which are in turn oxidized to formyl morpholide, can act as the corresponding reductants while the metal ions are reduced, depending on the reaction conditions. Apart from providing interesting mechanistic insights, the study points to the importance of a precise description of the composition of the chemical systems used, as well as the importance of seemingly inert auxiliaries, which turned out to be essential co-reactants in the metal (nano)particle generation. Graphic abstract

Evolution of the morphology of cellulose solutions in N-methylmorpholine-N-oxide during coagulation with a “soft” coagulant, isobutyl alcohol, at different temperatures is considered. Using optical interferometry and transmitted and scanning electron microscopy the mechanism of phase separation of the system to form a polymer phase is studied depending on the temperature of alcohol. It is shown that, in the case of a room temperature coagulant, a heterogeneous film with a droplet texture enlarging over thickness appears along the precipitation front. At a high temperature of alcohol the coagulation of the solution occurs in two stages. At the first stage the penetration of the coagulant into the jet of spinning solution leading to the formation of vacuoles occurs. The phase separation of the solution proceeds within the vacuoles as microreactors to form a polymer-concentrated shell and a polymer-diluted phase in the vacuole cavity. At the second stage the coagulant diffuses through the vacuole shell into the bulk of the solution and causes its uniform coagulation. The process of vacuole formation is visualized. The transverse cleavage of the film is analyzed by energy dispersive X-ray spectroscopy. The difference in the content of C, N, and O atoms on the walls of vacuoles and in the region of a film with a uniform cellular morphology is established.

In the lyocell process, N-methylmorpholine-N-oxide (NMMO) with a high recovery rate is used as a solvent to directly dissolve cellulose, which is of great significance for the realization of industrialization. In this paper, the impurity removal process and side reactions in the NMMO recovery system are introduced. The NMMO recovery system is generally composed of three major processes: air flotation, ion exchange and evaporation. Air flotation and ion exchange are the processes of removing impurities. And evaporation, where side reactions occur, is the process of increasing the concentration of NMMO. In terms of conductivity and colority, organic flocculants are better than inorganic flocculants in the air flotation process which mainly removes undissolved particulate matter, part of hemicelluloses and some colored substances. The ion exchange process mainly removes ionic substances and propyl gallate (PG). Side reactions occur during evaporation, producing colored substances and black particulate matter. Through analysis, it can be known that the production of colored substances is caused by the condensation reaction of N-methylmorpholine (NMM, 1), morpholine (M, 2), 2-Amino-4-methyl-oxazole (3), furfuryl alcohol (4), Morpholinoacetonitrile (5), xylose and NMMO under alkaline and high-temperature conditions, rather than by PG. The black particles are due to thermal degradation of NMMO or NMM or M in the presence of oxygen and iron at high temperatures.

Attenuated total reflection (ATR) ��� Fourier transform infrared (FTIR) spectroscopy with the pretreatment of converting the absorption spectrum into angle spectrum (CASAS) and partial least squares (PLS) was employed to rapidly and simultaneously determine the ingredients of cellulose slurries and solutions during lyocell production. ATR was employed to rapidly and conveniently collect the spectra of the swollen slurries and viscous solutions during production. CASAS was used to eliminate the influence on modeling by the optical path differences due to uneven ingredient distributions in the samples. The PLS models for the cellulose, water, and N-methylmorpholine N-oxide (NMMO) concentrations of the cellulose slurry/solution were constructed using the raw spectra, pretreated spectra by CASAS, and common pretreatment methods, respectively. The results show that CASAS eliminates interferences due to the differences in optical path and improves the performance of PLS model for each analyte. The standard errors of prediction (SEP) of models using CASAS for cellulose, NMMO, and water concentration of cellulose slurry were 0.368, 0.196 and 0.171, while the values for the cellulose solution were 0.442, 0.353, and 0.066, respectively. The standard errors of prediction (SEPs) of CASAS models are significantly lower than the reproducibility requirement of the reference method, 0.5. The reported approach using ATR-FTIR spectroscopy combined with CASAS and PLS is rapid and accurate for determining the ingredients of the cellulose slurries and solutions and offers potential for identifying similar samples.

In new biorefinery processes, NMMO/water is used for the pre-treatment of biomass to increase the efficiency of subsequent digestion processes, while GVL/water is used for “organosolv” fractionation of biomass. The combination of both methods, GVL digestion after pre-activation by NMMO, appears to be reasonable, but has not been successful. In the present study, we examine the reason for this failure and investigate the chemical processes in the ternary system NMMO/GVL/water and in the quaternary system NMMO/GVL/water/“biomass”. The consumption kinetics of NMMO and GVL at different temperatures, water contents and NMMO/GVL ratios were recorded. The respective degradation and reaction products were identified for the first time, by combining nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography – mass spectrometry (GC-MS) techniques and synthesis of authentic compounds for comparison. Decomposition products of NMMO and GVL on their own as well as reaction products of both components together (α-morpholinomethyl-GVL (7), α-methylene-GVL (8), and 4-hydroxyvaleric acid morpholide (13)) were observed among the main degradation products. At temperatures of 150 °C and at a water content

An important part of Lyocell fibers production is solvent recycling. Determining the content of the degradation products in the solvent will be helpful to select a reasonable solvent recovery proce...

The process of solid-phase dissolution of polyacrylonitrile copolymer containing ionic sulfo groups in an electron-donating solvent, N-methylmorpholine-N-oxide, is studied depending on its crystal hydrate form and preparation conditions. Optical studies of the transition of solid-phase copolymer–solvent systems to a viscous flow state make it possible to construct solubility curves and reveal stages of morphological transformations during dissolution, explaining their nature. Solid-phase mixed systems are studied by IR spectroscopy, and interactions of the functional groups of the copolymer with various crystal hydrates of the solvent are analyzed both during standard mechanical mixing and mechanochemical activation under intense shear deformation, which predetermines the formation of solid solutions.

Interaction between N-methylmorpholine N-oxide (NMMO), H2O, and the titanium dioxide (TiO2) surface was studied by spectral tests and molecular dynamics simulations as the theoretical foundation for the development of functional lyocell. The molecular structure, movement, and arrangement of the NMMO and water molecules, as well as the interaction energies between them, were characterized. The results show that both water and NMMO molecules can interact with the TiO2 surface, and the water molecule is stronger, which makes the water molecules near the TiO2 surface different from that of the bulk solution. With the increase of the NMMO concentration, NMMO molecules compete with the water molecules adsorbed on the TiO2 surface, and two adsorption conformations of NMMO on the TiO2 surface were found. When the NMMO concentration is higher than 50%, the N-O bond of NMMO is the main position interacting with the TiO2 surface, forming a more stable and complex adsorption molecular layer and enhancing the interaction between TiO2 and the solution, and finally promote the dispersion of TiO2 particle and increase the zero-shear viscosity of the lyocell solution. At the same time, the strong interaction also weakens the N-O bond of the NMMO molecules near the TiO2 surface with the bond length increasing; however, the influence cannot cause instability of NMMO. UV spectra also shows that there is no NMMO decomposition due to the addition of TiO2 during the dissolution process. In conclusion, NMMO can promote the dispersion of the TiO2 nanoparticles in the solvent, and the stability of NMMO is not affected, which is the basis for the preparation of the functional lyocell fiber.

Abstract The cellulose solvent N-methylmorpholine-N-oxide monohydrate (NMMO) reacts violently with carbodiimide coupling agents, such as the widely used DCC (dicyclohexylcarbodiimide) and EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide), which can cause explosions, heavy smoke generation and complete charring of the reaction mixtures. For this reason it is clear that cellulose or other carbohydrates dissolved in NMMO (“Lyocell conditions”) cannot be safely esterified or amidified under DCC/EDC conditions. It is important to note that cellulosic material regenerated from NMMO solutions also poses a risk if it contains residual NMMO, which can then come into contact with DCC-type coupling agents in non-aqueous media, as recent accidents have unfortunately shown. Similarly, EDC/DCC traces in cellulose can have detrimental effects when trying to dissolve the material in NMMO. Working in aqueous systems generally reduces the risk of uncontrolled reactions, while alcohols or aprotic solvents are not very effective in this regard. Washing for NMMO removal or EDC/DCC removal should therefore always be carried out by aqueous media, if any possible, if there is a potential risk that the reagents might come into contact later. This warning describes the potential hazards of the reagent combination, highlights the underlying degradation mechanism and explains the precautions to be taken to avoid any “exothermic events”. Graphic abstract

Разработан метод получения новых гидратцеллюлозных волокон из растворов льняной целлюлозы в N-метилморфолин-N-оксиде с использованием твердофазного способа активации целлюлозы растворителем. Исследована растворимость льняной целлюлозы в данном растворителе, проведен сравнительный анализ реологического поведения растворов льняной и древесной целлюлозы и определены оптимальные температурно-концентрационные условия получения гидратцеллюлозных волокон. Исследование структуры методами РСА и ИК-Фурье спектроскопии свидетельствует о более выраженном структурном упорядочении волокон, сформованных из льняной целлюлозы по сравнению с волокнами, полученными из Байкальской древесной целлюлозы. Механические характеристики новых волокон находятся на уровне промышленных гидратцеллюлозных образцов, что позволяет рассматривать льняную целлюлозу как альтернативный источник сырья для формования гидратцеллюлозных волокон, способных играть роль пре- курсоров углеродных волокон.

In this work, an environmental micro-dissolution method to prepare Fe3O4 NPs@cotton composite fabrics without using binders is reported. The controlled N-methylmorpholine N-oxide (NMMO) treatment can micro-dissolve superficial layers of fibers through the strong hydrogen bonding force. The micro-dissolved superficial layers themselves can work like glue to physically adhere surrounding Fe3O4 NPs and then these Fe3O4 NPs can be embedded onto the layers. In the subsequent heating treatment, the micro-dissolved superficial layers would physically re-coagulate, immobilizing Fe3O4 NPs onto fibers’ surface. The as-obtained Fe3O4 NPs@cotton composite fabrics were systematically characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Additionally, through vibrating sample magnetometry tests, the Fe3O4 NPs@cotton fabrics exhibit para-magnetism, and the saturation magnetization can remain up to 90% after 20 washing cycles. Thermal gravimetric analysis and moisture absorption tests show that there are no obvious influences on thermal stability and moisture absorption capability of cotton fabrics. Even noticeable enhancements in mechanical properties can be observed.

Fibers of bacterial cellulose were obtained for the first time from solutions in N-methylmorpholine N-oxide (NMMO) by using the concept of solid-phase dissolution of bacterial cellulose. The mechanism of solid-phase dissolution of bacterial cellulose in NMMO is examined with due regard to the structural and morphological characteristics of native bacterial cellulose. By investigating the structure of the fibers it was possible to reveal the different orientation of the main diffraction planes of the outer shell and inner part of the fiber reflecting the structural aspect of the shell–core morphology. The fibrillar morphology of the fiber was established by scanning electron microscopy. The thermal characteristics of the fibers of bacterial cellulose differ radically from the characteristics of fibers of plant origin in the preponderance of condensation processes that produce exo effects on the thermograms and lead to increase of the carbon residue. The mechanical characteristics of the obtained fibers were characterized.

The process of film formation including the initial treatment of thin layers of cellulose solutions in N-methylmorpholine N-oxide with isobutanol followed by washing with water is investigated in detail, and the structural and morphological features of the obtained films are examined. The phase state of the N-methylmorpholine N-oxide–isobutyl alcohol system is studied by differential scanning calorimetry and optical interferometry, and a diagram describing the crystalline equilibrium and allowing determination of the temperature–concentration “window” of compatibility of components is constructed. The dependence of viscosity of N-methylmorpholine N-oxide solutions in isobutanol on temperature confirms the phase composition of the system. The process of film formation is modeled by analyzing the diffusion zone of the cellulose solution–isobutyl alcohol system. The IR study of the interaction of N-methylmorpholine N-oxide containing 13.3% water with isobutanol shows that the affinity of isobutanol for water is much higher than that for N-methylmorpholine N-oxide. For this reason, when the spinning solution is brought in contact with isobutanol, the redistribution of water between the interacting components occurs and the structure of the heterogeneous gel-like complex cellulose–N-methylmorpholine N-oxide–isobutanol “is frozen,” as proved by the X-ray diffraction study of the films. Complete removal of the solvent and isolation of cellulose from this film proceed only upon subsequent washing with water. The X-ray diffraction and optical interferometry study of the effect of temperature on the interaction of a hot cellulose solution with cold isobutanol suggests that at room temperature the film obtained from solution contains inclusions of the vitrified N-methylmorpholine N-oxide. Under isothermal conditions (at a temperature of 90°С), the rate of interdiffusion grows appreciably and the solution preserves the homogeneous structure. Thus, the precipitation of cellulose from the bicomponent solvent N-methylmorpholine N-oxide–water upon contact first with isobutanol and then with water proceeds via two stages: initially the system undergoes phase separation and a concentrated solution is formed in the isobutanol-N-methylmorpholine N-oxide blend, from which cellulose precipitates upon interaction with water. When the process of primary interaction of the solution with alcohol is conducted under the conditions of compatibility of isobutanol with N-methylmorpholine N-oxide, a more homogeneous morphology of the films can be obtained.

Structural and morphological evolution of polyacrylonitrile (PAN) samples from starting powder of a ternary copolymer to fibers produced from concentrated solutions of PAN in N-methylmorpholine-N-oxide (NMMO) was studied using x-ray diffraction for the first time. X-ray exposures in transmission and reflection geometries allowed the structures of outer and inner parts of the PAN fibers to be differentiated. It was shown that a shell—core structure formed in the precipitation bath during fiber spinning. A comparison of x-ray diffraction patterns of fibers spun using the NMMO process and industrial samples spun from DMSO and aqueous sodium thiocyanate solutions did not reveal fundamental structural differences.

Uniformly-sized porous cellulose beads functionalized with amidoxime groups were prepared for the first time using a microfluidic method with N-methylmorpholine N-oxide (NMMO) monohydrate as a cellulose solvent. The molten state cellulose dope in NMMO monohydrate (cell/NMMO dope) as a disperse phase and hot mineral oil as a continuous phase were used in a T-junction microfluidic chip to produce uniformly-sized cell/NMMO droplets. Coagulation of the molten state cell/NMMO droplet at high temperature and amidoxime functionalization could prepare the highly-porous spherical amidoxime-functionalized cellulose beads with a uniform fibrous open internal structure. The prepared amidoxime-functionalized cellulose beads showed excellent metal adsorption properties with a maximum adsorption capacity of ~ 80 mg g− 1 in the case of Cu2+/phthalate ions. The newly developed highly-porous cellulose beads can open many new applications with other proper functionalization at the reactive hydroxyl groups of the cellulose.

Replacing the aqueous coagulation bath with an alcoholic one during spinning cellulose fibers (films) from solutions in N-methylmorpholine-N-oxide leads to a radical restructuring of the hydrogen bonds net of cellulose and, as a result, to a change in the structure and properties of the resulting material. By the method of optical interferometry, it was possible to identify the intrinsic features of the interaction of the solvent and isomeric alcohols and to construct phase diagrams of binary systems describing the crystalline equilibrium. Knowledge of the phase states of the system at different temperatures renders it possible to exclude the process of solvent crystallization and conduct the spinning in pseudo-homogeneous conditions. The structure and morphology of samples were studied using X-ray diffraction and scanning electron microscopy methods for a specific coagulant. When the solution under certain conditions is coagulated at contact with alcohol, the solvent may be in a glassy state, whereas, when at coagulation in water, an amorphous-crystalline structure is formed. The structural features of cellulose films obtained by coagulation of solutions with water and alcohols help to select potential engineering or functional materials (textile, packaging, membranes, etc.), in which their qualities will manifest to the best extent.

In the present study, one of the possible methods of the bacterial cellulose processing is proposed via its dissolution in N-methylmorpholine-N-oxide using the stage of mechano-chemical activation of the solid polymer&ndash, solvent system. Preliminary solid-phase activation is apparently a decisive factor affecting the dissolution rate of bacterial cellulose in N-methylmorpholine-N-oxide. The effects of bacterial cellulose concentration, solvent nature, degree of polymerization and temperature on dissolution time were studied. The rheological behavior of the solutions does not change at 120 &deg, C for at least half an hour that allowed us to process such solutions for films preparation. The films from these solutions by means of dry-wet jet spinning in aqueous coagulant were formed. The structure of the nascent cellulose and formed films was tested by the X-ray diffraction method and SEM. The thermal behavior of the films revealed an increase in the carbon yield for the formed films compared to the nascent bacterial cellulose. The process of film pyrolysis is accompanied by exothermic effects, which are not typical for wood cellulose. Some reasons of such thermal behavior are considered.

The combined solutions of cellulose and PAN in N-methylmorpholine-N-oxide at total polymer contents of 18 and 25% are obtained by solid-phase dissolution. The investigation of phase composition and morphology of these systems via optical methods shows that the solutions of cellulose and PAN in N-methylmorpholine-N-oxide are incompatible and form emulsions. The action of deformation on the emulsions leads to the appearance of orientational effects. If PAN predominates in droplets of the dispersed phase of cellulose solutions, this leads to the formation of fibrillar structures under shear stress, while in the case of PAN dispersion medium double emulsions are formed, in which internal droplets of the cellulose solution are most easily extended under shear. The rheological behavior of the combined systems is the direct consequence of structural-morphological transformations proceeding during deformation of the system. An analysis of the morphological and rheological features of heterophase systems reveals the concentration interval for the moldability of composite fibers from spinning emulsions.

It is shown that alkylation of pyrazoles with (E)/(Z)-1,3-dichlorobut-2-enes can be carried out in an alkaline aqueous medium in the presence of N-methylmorpholine N-oxide. In some cases, this technique may substitute phase-transfer catalysis. Conformational analysis of the reaction products showed that a mixture of (E)/(Z) isomers is formed in a ratio of 9:1.

The objective of the presented research was to determine the influence of cellulose coating, obtained from the cellulose solution in N-Methylmorpholine N-oxide (NMMO), on the structural and mechanical properties of paper. The effect of heating time of paper samples coated with cellulose dissolved in NMMO was also investigated. Depending on the heating time of the coating, a continuous or porous layer was obtained. Coating without any heating stage yielded a continuous cellulose layer of hydrophobic properties (higher contact angle in comparison to base paper), and paper of higher smoothness and increased tear resistance. Analysis of the paper samples showed that cellulose coating not only changed the surface properties of paper, but also significantly improved paper strength properties, such as the tensile index, elongation, bursting strength index and double folds number. Despite the process’ limitations (e.g. necessity of removing the NMMO), this method can be considered as a novel approach for paper property modification.

Phase separation of polymer solutions initiated by the addition of a nonsolvent is the main method for the preparation of polymer membranes. Depending on the application, such membranes must have a different pore size, which depends on the numerous parameters of the forming process. The liquid–liquid phase separation has been considered for cellulose solutions in N-methylmorpholine N-oxide (NMMO) interacting with various alcohols (methyl, ethyl, isopropyl, and isobutyl). Kinetics of cellulose regeneration was investigated by laser interferometry technique to understand the mechanism of cellulose film structure formation in the NMMO process. Influence of temperature, coagulant nature, and cellulose content on the process kinetics and morphology of the films was studied and corresponding interdiffusion coefficients were calculated. Based on the solubility parameters, triple phase diagrams of the systems were calculated. Formation of different morphologies was explained primarily by the different position of the composition path, the bimodal curve, and the gelation line in the phase diagrams. The second important parameter was the different rate of mutual diffusion of the NMMO and coagulants, due to the difference in the viscosity of the latter. Using methanol or ethanol as coagulation baths leads to obtaining the nanoporous structure of cellulose films, whereas isopropanol and isobutanol favors macropore formation.

Composite fibers were prepared by solid-state dissolution of cellulose in N-methylmorpholine-N-oxide with added tetraethoxysilane (TEOS). It was shown that adding TEOS to the cellulose matrix increased up to 16% the fiber carbon residue during heat treatment. Bonds formed between Si and C during their high-temperature treatment according to IR spectra of the composite cellulose fibers. The thermal behavior of the fibers was studied using TGA and TMA. The fiber morphology and the structure of the Si-containing additive particles were examined using SEM and TEM. The mechanical properties of carbon fibers prepared from cellulose-hydrate and composite fibers were compared.

Highly concentrated solutions of acrylonitrile copolymers (PAN) in N-methylmorpholine N-oxide (NMMO) were obtained via the solid-phase activation method. Specific interactions in the system at different stages of the dissolution process starting from solid-state activation and finishing with a transition to a viscous state were studied by IR spectroscopy, polarizing microscopy, interferometry and rheology. It was shown that the crucial factor determining a possibility of dissolution is the complex formation between carboxyl groups in the copolymer and the electron-donor N → O group in the solvent. This complex arises during the process of solid-phase activation of PAN and crystalline NMMO, which thereafter melts and transforms into a homogeneous solution having viscoelastic behavior. In the temperature range of 130–135 °C, irreversible chemical transformations take place in the solutions due to the coherent interaction between nitrile groups; these reactions lead to the formation of cyclic structures and conjugated sequences in the PAN chains. Rheological properties follow this process via specific viscosity and viscoelasticity evolution in time.

N-Methylmorpholine-N-oxide (NMMO) cannot be completely separated by extraction from mixtures with common 1,3-dialkylimidazolium ionic liquids (ILs) due to strong ionic interactions between the two components. At elevated temperatures, above approx. 90 °C, especially under dry conditions and in the presence of acid, alkylating or acylating agents, remaining NMMO in ILs tends to undergo autocatalytic degradation. This is a highly exothermic, unstoppable process that results in explosions, flames, and complete charring of the reaction mixtures. Thus, caution must be exercised when drying or heating ILs that were in previous contact with NMMO, and the absence of amine oxide must be confirmed to avoid potential danger.

A type of cellulose solvent, i.e., aqueous N-methylmorpholine- N-O xide (NMMO) solutions, was used to modify cellulose nanocrystal (CNC) photonic films. CNC films can be swollen by NMMO, resulting in red-shifted reflected colors. The swelling effect is supposed to come from NMMO permeation into the crystalline regions of individual CNCs and intercalating in between CNC particles. When NMMO was removed, the reflected colors of CNC films blue shifted because of the reduced helical pitches. NMMO-treated CNC films display reversible responsive colors to humidity changes in several minutes. Increasing NMMO content allows CNC films to enlarge the responsive color range. Aqueous NMMO can be used as an ink to depict responsive photonic patterns on CNC films. This post-treatment approach to producing responsive colors and photonic patterns in CNC films may be applied to the areas of sensor, anti-counterfeiting, and decoration.

Alkali cellulose is an important intermediate in the production of cellulose derivatives. N-methylmorpholine-N-oxide (NMMO)/H2O was used as a homogeneous reaction medium for the cellulose alkalization process to intensify the alkalization degree and improve the substitution uniformity. The morphology, specific surface area and crystalline structure of pristine cellulose, the as-synthesized alkali cellulose and dissolved-regenerated cellulose were characterized by SEM, BET, XRD and FT-IR, respectively. The results showed that the homogeneous reaction medium not only offered a low mass transfer resistance, but also facilitated a disruption of the hydrogen bond in cellulose, thus resulting in the transformation of the cellulose structure from complicated stacking chains to simple glucose chains. The interior hydroxyl groups in the cellulose became accessible to the alkaline reagent NaOH to enhance the alkalization process for the increase in bonding alkali content and the improvement in substitution uniformity. The bonding alkali content was calculated by the difference between total added alkali and free alkali and was achieved as 0.61 g/g cellulose at the optimized operation conditions: reaction temperature of 95 °C, reaction time of 90 min, NMMO dosage of 90.00 g, cellulose 1.0 g and NaOH concentration of 1.40 wt%. Meanwhile, in the conventional alkalization process, the bonding alkali content was just 0.41 g/g cellulose. The alkali cellulose prepared in NMMO/H2O medium has a large specific surface area of 125 m2 g−1 and an extremely low crystallinity degree. The NMMO/H2O system represents a potential homogeneous solvent for the cellulose alkalization process.

We present a method for synthesis of silver nanoparticles in N-methylmorpholine N-oxide (NMMO) and the associated mechanism, as well as their use for in situ volume modification of cellulose fibers. The synthesized particles had diameter of about 4 nm, and their colloid solution was stable for 1 year. The nanoparticles were stabilized using polyethylenimine, which apart from preventing nanoparticle agglomeration, also accelerated Ag+ ion reduction and prevented NMMO degradation. A mechanism for the nanoparticle synthesis is suggested based on the electrochemical potentials of all ions in solution, with perhydroxyl ions resulting from NMMO reducing the silver ions. We also created nanocomposites from fibers and silver nanoparticles, in which the latter showed very good dispersion in the fiber volume. Such spun fibers showed improved mechanical parameters in comparison with unmodified fibers.

The dissolution of cellulose in N-methylmorpholine-N-oxide monohydrate and the dissolution of N-methylmorpholine-N-oxide monohydrate in water have been studied via optical interferometry. A part of the phase diagram for the cellulose/N-methylmorpholine-N-oxide system has been constructed. The phase diagram is characterized by crystalline equilibrium, hysteresis of the melting temperatures of the solvents, and a region of anisotropy. Optical interferometry has been used for the first time to study the kinetics of cellulose coagulation during the interaction of cellulose solutions in N-methylmorpholine-N-oxide with water and water solutions of N-methylmorpholine-N-oxide. Information on the values of interdiffusion coefficients and the morphologies of the resulting cellulose films has been obtained. The possibility to use optical interferometry to analyze the interaction of a solution with the coagulating agent in the case of cellulose fiber and film formation has been demonstrated. The influences of temperature, the nature of the coagulating agent, and the cellulose content on the kinetics of the process and morphologies of the formed films have been shown. The use of N-methylmorpholine-N-oxide as a part of the coagulation system decreases the rate of interdiffusion of solutions, thereby resulting in a more uniform and dense morphology of cellulose films. Increased temperature causes diffusion acceleration, thereby leading to the formation of an anisotropic morphology of the cellulose films.

In this work, the novel chitosan derivative ethylamine hydroxyethyl chitosan (EHC) was synthesized and blended with cellulose in an aqueous N-methylmorpholine-N-oxide (NMMO) solution in order to fabricate antibacterial chitosan/cellulose fiber. The rheological behaviors of the obtained co-solution in both steady and dynamic states were carefully investigated to determine the spinnability of the co-solution. In steady state, the addition of EHC was found to preserve the power-law flow characteristics of cellulose in the aqueous NMMO solution, while broadening the first Newtonian fluid-flow area. Under dynamic conditions, both Han-plot and viscoelastic analyses indicated the homogeneity of the co-solution. EHC/cellulose antibacterial fibers were successfully spun via the lyocell process using aqueous NMMO as the solvent, confirming the excellent spinnability of the EHC/cellulose co-solution. Scanning electron microscopy was used to observe the morphology of the obtained EHC/cellulose fibers; they were also investigated for antibacterial activity. The obtained EHC/cellulose fiber exhibited good spinning consistency and strong antibacterial activity against Escherichia coli, demonstrating potential applications for the material in antibacterial textiles.