Impact of non‐solvent on regeneration of cellulose dissolved in 1‐(carboxymethyl)pyridinium chloride ionic liquid

Cellulose dissolved in ionic liquid (1‐(carboxymethyl)pyridinium chloride)/water (60/40 w/w) mixture is regenerated in various non‐solvents, namely water, ethanol, methanol and acetone, to gain more insight into the contribution of non‐solvent medium to the morphology of regenerated cellulose. To this end, the initial and regenerated celluloses were characterized with respect to crystallinity, thermal stability, chemical structure and surface morphology using wide‐angle X‐ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. According to the results, regardless of non‐solvent type, all regenerated samples have the same chemical structure and lower crystallinity in comparison to the initial cellulose, making them a promising candidate for efficient biofuel production based on enzymatic hydrolysis of cellulose. The reduction in crystallinity of regenerated samples is explained based on the potential of the non‐solvent to break the hydrogen bonds between cellulose chains and ionic liquid molecules as well as the affinity of water and non‐solvent which can be evaluated based on Hansen solubility parameter. The latter also determines the phase‐separation mechanism during the regeneration process, which in turn affects surface morphology of the regenerated cellulose. The pivotal effect of regenerated cellulose crystallinity on its thermal stability is also demonstrated. Regenerated cellulose with lower crystallinity is more susceptible to molecular rearrangement during heating and hence exhibits enhanced thermal stability. © 2019 Society of Chemical Industry     

Rheology of 1‐butyl‐3‐methylimidazolium chloride cellulose solutions. II. Solution character and preparation

The focus of this article of a three part series is the effects of preparation and composition on the shear rheology of cellulose in the ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl). Included are the effects of three different degrees of polymerization, (i.e., average molecular weight), manual versus high shear mixing, a range of cellulose concentrations, and the effects of controlled amounts of lignin and a hemicellulose. The rheology implies that a gel phase develops at higher degrees of polymerization, higher concentration, and at lower temperatures. The first article focused primarily on shear rheology of cellulose in [Bmim]Cl with a high shear preparation technique, one degree of polymerization, a narrow range of cellulose concentrations, and temperature. The third article focuses on elongational rheology of cellulose in [Bmim]Cl. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

麦秸纤维素在离子液体与有机溶剂复合体系中的溶解

采用一步法合成了N-烯丙基吡啶氯盐离子液体([APy]Cl),用傅里叶变换红外光谱(FT-IR)和质谱分析(MS)进行结构表征,并与5种有机溶剂[二甲基亚砜(DMSO)、N,N-二甲基甲酰胺(DMF)、N,N-二甲基乙酰胺(DMAC)、吡啶及BS-12]形成复合溶剂,考察了麦秸纤维素在其复合溶剂中的溶解性能。结果表明:质量分数2%的麦秸纤维素在[APy]Cl/DMSO复合溶剂中溶解性能较佳,当复合溶剂m([APy]Cl)∶m(DMSO)=1∶0.5、120℃时,75 min可溶解完全。利用IR和X射线衍射对再生前后的纤维素进行结构表征,可知[APy]Cl/DMSO复合溶剂对麦秸纤维素溶解为直接溶解过程,溶解后麦秸纤维素由晶型Ⅰ转变成晶型Ⅱ。     

High‐strength regenerated cellulose fibers spun from 1‐butyl‐3‐methylimidazolium chloride solutions

High‐performance regenerated cellulose fibers were prepared from cellulose/1‐butyl‐3‐methylimidazolium chloride (BMIMCl) solutions via dry‐jet wet spinning. The spinnability of the solution was initially evaluated using the maximum winding speed of the solution spinning line under various ambient temperatures and relative humidities in the air gap. The subsequent spinning trials were conducted under various air gap conditions in a water coagulation bath. It was found that low temperature and low relative humidity in the air gap were important to obtain fibers with high tensile strength at a high draw ratio. From a 10 wt % cellulose/BMIMCl solution, regenerated fibers with tensile strength up to 886 MPa were prepared below 22 °C and relative humidity of 50%. High strengthening was also strongly linked with the fixation effect on fibers during washing and drying processes. Furthermore, an effective attempt to prepare higher performance fibers was conducted from a higher polymer concentration solution using a high molecular weight dissolving pulp. Eventually, fibers with a tensile strength of ～1 GPa and Young's modulus over 35 GPa were prepared. These tensile properties were ranked at the highest level for regenerated cellulose fibers prepared by an ionic liquid–based process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45551.     

Regenerated and graft copolymer fibers from steam-exploded wheat straw: Characterization and properties

Steam explosion treatment has been proven to effectively induce such marked modifications to the chemical and supramolecular structure of wheat straw cellulose as to make this cellulose a suitable raw for dissolving processes. Regenerated and poly(acrylonitrile) (PAN) and poly(methyl methacrylate) (PMMA) grafted wheat straw fibers obtained on the laboratory scale were characterized by various techniques (X-ray diffraction, cross polarization-magic angle spinning (CP-MAS) ¹³C nuclear mag-netic resonance and vibrational spectroscopy, scanning electron microscopy, differential scanning calorimetry), and the relationships between the morphological–structural features and physicomechanical and end-use properties have been evidenced. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:961–974, 1998     

Rheology of 1‐butyl‐3‐methylimidazolium chloride cellulose solutions. III. Elongational rheology

The elongational rheology of solutions of cellulose in the ionic liquid solvent 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) was measured at 80, 90, and 100°C; 8, 10, and 12 wt% cellulose; Hencky strains 5, 6, 7; and strain rates from 1 to 100 s^?1. Master curves were generated by shifting the elongational viscosity curves with respect to temperature and Hencky strain. Also, general master curves were generated by simultaneously shifting with respect to both temperatures and Hencky strain. From the Arrhenius plots of the temperature shift factors, the activation energy for elongational flow was determined. The elongational rheology of these solutions was elongational strain rate thinning similar to that of their shear behavior and polymer melts and they were also strain hardening. Both effects and the viscosity increased with cellulose concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Rheology of 1‐butyl‐3‐methylimidazolium chloride cellulose solutions. I. Shear rheology

In this article, shear rheology of solutions of different concentrations obtained by dissolution of cellulose in the ionic liquid (IL) solvent 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) was studied by measuring the complex viscosity and dynamic moduli at different temperatures. The obtained viscosity curves were compared with those of lyocell solutions and melt blowing grade polypropylene melts of different melt flow rates (MFR). Master curves were generated for complex viscosity and dynamic moduli by using Carreau and Cross viscosity models to fit experimental data. From the Arrhenius plots of the shift factors with respect to temperature, the activation energies for shear flow were determined. These varied between 18.99 and 24.09 kCal/mol, and were compared with values for lyocell solutions and different polymeric melts, such as polyolefins, polystyrene, and polycarbonate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

离子液体法制备再生细菌纤维素纤维

以离子液体(氯化1-甲基-3-正丁基咪唑)溶解高聚合度细菌纤维素(BC),采用湿法纺丝制备再生细菌纤维素(RBC)初生纤维;通过红外光谱分析(FTIR)、广角X射线衍射(WAXD)分析、热失重(TG)分析、扫描电镜( SEM)、单丝强度拉伸等表征了RBC初生纤维的结构和性能.结果表明:该溶剂体系通过10 h的快速搅拌溶...     

All‐wood biocomposites by partial dissolution of wood flour in 1‐butyl‐3‐methylimidazolium chloride

After cedar‐derived wood flour (WF) and bark flour (BF) were mixed with 1‐butyl‐3‐methylimidazolium chloride (BMIC) at 100°C, the obtained compounds with BMIC content 40 wt % were compression‐molded at 210°C to give WF/BMIC and BF/BMIC composites, respectively. The BMIC contained in the composites was twice extracted with ethanol at 60°C to afford WF/BMIC‐E and BF/BMIC‐E biocomposites, which were subsequently annealed at 200°C for 24 h to produce WF/BMIC‐A and BF/BMIC‐A biocomposites. The Fourier transform infrared spectroscopic analysis revealed that WF has a higher content of cellulose and a lower content of lignin than BF does, and that the BMIC content diminished by the extraction process. The scanning electron microscopy analysis showed that woody particles joined together by the compression molding of WF/BMIC and BF/BMIC compounds, and that the extraction of BMIC roughened the surface and the annealing again smoothed the surface due to the fusion of the residual BMIC and woody particles. The XRD measurements indicated that the annealing enhanced the crystallinity of cellulose component. The tensile properties and 5% weight loss temperature of the biocomposites were considerably improved by the extraction of BMIC and further by the annealing. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crystallization behavior and isothermal crystallization kinetics of PLLA blended with ionic liquid, 1‐butyl‐3‐methylimidazolium dibutylphosphate

The crystallization behavior and isothermal crystallization kinetics of neat poly(l ‐lactic acid) (PLLA) and PLLA blended with ionic liquid (IL), 1‐butyl‐3‐methylimidazolium dibutylphosphate, were researched by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and wide angle X‐ray diffraction (WXRD). Similar to the non‐isothermal crystallization behavior of neat PLLA, when PLLA melt was cooled from 200 to 20°C at a cooling rate of 10°C min^?1, no crystallization peak was detected yet with the incorporation of IL. However, the glass transition temperature and cold crystallization temperature of PLLA gradually decreased with the increase of IL content. It can be attributed to the significant plasticizing effect of IL, which improved the chain mobility and cold crystallization ability of PLLA. Isothermal crystallization kinetics was also analyzed by DSC and described by Avrami equation. For neat PLLA and IL/PLLA blends, the Avrami exponent n was almost in the range of 2.5–3.0. It is found that t_1/2 reduced largely, and the crystallization rate constant k increased exponentially with the incorporation of IL. These results show that the IL could accelerate the overall crystallization rate of PLLA due to its plasticizing effect. In addition, the dependences of crystallization rate on crystallization temperature and IL content were discussed in detail according to the results obtained by DSC and POM measurements. It was verified by WXRD that the addition of IL could not change the crystal structure of PLLA matrix. All samples isothermally crystallized at 100°C formed the α‐form crystal. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41308.     

Investigations on esterification reactions of starches in 1‐N‐butyl‐3‐methylimidazolium chloride and resulting substituent distribution

The ionic liquid (IL) 1‐N‐butyl‐3‐methylimidazolium chloride ([C₄mim]⁺Cl^?) was used as solvent for different esterification reactions of the biopolymer starch. Therefore, maize starches with varying content of amylose were used. Different carboxylic acid anhydrides were applied to esterify starch with a degree of substitution (DS) in the range of 0.7–3.0. For example, starch acetates with the mentioned DS are accessible within 30 min at a 105°C‐reaction temperature. The DS distribution of starch acetates synthesized in IL was compared with the common starch acetate synthesis of Mark and Mehltretter. Also, a consideration of starch acetates and cellulose acetates synthesized in [C₄mim]⁺Cl^? is given. The starch esters were characterized by means of Raman spectroscopy for qualitative‐ and nuclear magnetic resonance spectroscopy for quantitative determination of the functionalization pattern. Moreover, the molecular mass distribution was determined after saponification by means of GPC‐MALLS. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Evaluation of 1‐ethyl‐3‐methylimidazolium acetate based ionic liquid systems as a suitable solvent for collagen

Collagen, a prominent biopolymer, which is famous for its excellent biological activity, has been used extensively for tissue engineering applications. In this study, a novel solvent system for collagen was developed with an ionic liquid, 1‐ethyl‐3‐methylimidazolium acetate ([EMIM][Ac]), solvent system. A series of sodium salts were introduced into this solvent system to enhance collagen's dissolution procedure. The results show that the solubility of collagen was significantly influenced by the temperature and sodium salts. The solubility reached up to approximately 11% in the [EMIM][Ac]/Na₂HPO₄ system at 45°C. However, the structure of the regenerated collagen (Col‐regenerated) may have been damaged. Hence, we focused on the structural integrity of the collagen regenerated from the [EMIM][Ac] solvent system by the methods of sodium dodecyl sulfate–polyacrylamide gel electrophoresis, Fourier transform infrared spectroscopy, ultrasensitive differential scanning calorimetry, atomic force microscopy, X‐ray diffraction, and circular dichroism because its signature biological and physicochemical properties were based on its structural integrity. Meanwhile, a possible dissolution mechanism was proposed. The results show that the triple‐helical structure of collagen regenerated from the [EMIM][Ac] solvent system below 35°C was retained to a large extent. The biocompatibility of Col‐regenerated was first characterized with a fibroblast adhesion and proliferation model. It showed that the Col‐regenerated had almost the same good biological activity as nature collagen, and this indicated the potential application of [EMIM][Ac] in tissue engineering. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2245–2256, 2013     

Microwave assisted glycolysis of poly(ethylene terephthalate) catalyzed by 1‐butyl‐3‐methylimidazolium bromide ionic liquid

The combination of ionic liquid (IL) associated with microwave energy may have some potential application in the chemical recycling of poly (ethylene terephthalate). In this processes, glycolysis of waste poly (ethylene terephthalate) recovered from bottled water containers were thermally depolymerized with solvent ethylene glycol (EG) in the presence of 1‐butyl‐3‐methyl imidazolium bromide ([bmim]Br) as catalyst (IL) under microwave condition. It was found that the glycolysis products consist of bis (2‐hydroxyethyl) terephthalate (BHET) monomer that separated from the catalyst IL in pure crystalline form. The conversion of PET reach up to 100% and the yield of BHET reached 64% (wt %). The optimum performance was achieved by the use of 1‐butyl‐3‐methyl imidazolium bromide as a catalyst, microwave irradiations temperature (170–175°C) and reaction time 1.75–2 h. The main glycolysis products were analyzed by ¹H NMR, ¹³C NMR, LC‐MS, FTIR, DSC, and TGA. When compared to conventional heating methods, microwave irradiation during glycolysis of PET resulted in short reaction time and more control over the temperature. This has allowed substantial saving in energy and processing cost. In addition, a more efficient, environmental‐friendly, and economically feasible chemical recycling of waste PET was achieved in a significantly reduced reaction time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41666.     

Regenerated cellulose nanocomposites reinforced with exfoliated graphite nanosheets using BMIMCL ionic liquid

Green nanocomposites of regenerated cellulose/exfoliated graphite nanosheets films with low nanofiller loadings were prepared using environmentally benign 1-butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid. X-ray diffraction revealed well developed intercalated nanocomposites. The tensile strength and Young's modulus of the prepared nanocomposites were increased by 97.5% and 172% respectively when 0.75 wt.% and 1 wt.% exfoliated graphite nanosheets were added. The results were validated using the Halpin–Tsai model. The exfoliated graphite nanosheets were unidirectionally aligned in the regenerated cellulose parallel to the surface of the nanocomposites as revealed by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Also, the TEM and FESEM revealed uniform dispersion of the exfoliated graphite nanosheets and good interaction between the nanofillers and the matrix. The addition of the exfoliated graphite nanosheets enhanced the thermal stability and reduced the water absorption and diffusivity of the nanocomposites.     

Rheological properties of cotton pulp cellulose dissolved in 1‐butyl‐3‐methylimidazolium chloride solutions

Rheological properties of cotton pulp dissolved in 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) solutions were characterized using an advanced rheometer. The complex viscosity, dynamic modulus, and shear viscosity at different temperature were studied. In the steady shear measurements, all the solutions show a shear‐thinning behavior at high shear rates. The complex viscosity as a function of frequency was fitted by extended Carreau–Yasuda model. In all cotton pulp/[Bmim]Cl solutions, the complex dynamic viscosity (η*) and steady shear viscosity (η_a) followed the Cox–Merz rule only at lower frequency. The effects of tested temperature on viscosity and viscoelastic behavior of the solutions were also investigated. The value of activation energy for the dissolution of cotton pulp in ionic liquids was 65.28 kJ/mol at the concentration of 10 wt% and was comparable with the ones for the dissolution of cellulose in NMMO. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

纤维素在离子液体1-丁基-3-甲基-咪唑乙酸盐中的溶解性能

研究了纤维素在离子液体1-丁基-3-甲基-咪唑乙酸盐([BMIM] CH3COO)中的溶解性能.结果表明,[ BMIM] CH3COO对天然纤维素有较好的溶解能力,再生得到纤维素膜;随着溶解温度的升高,溶解时间大大缩短.采用红外光谱(FT-IR)、热质量损失分析(TGA)、X-射线衍射(XRD)等对再生前后纤维素进行了...     

Rheological characterization of concentrated cellulose solutions in 1‐allyl‐3‐methylimidazolium chloride

The rheological properties of high concentrated wood pulp cellulose 1‐allyl‐3‐methy‐limidazolium Chloride ([Amim]Cl) solutions were investigated by using steady shear and dynamic viscoelastic measurement in a large range of concentrations (10–25 wt %). The measurement reveals that cellulose may slightly degrade at 110°C in [Amim]Cl and the Cox–Merz rule is valid for 10 wt % cellulose solution. All of the cellulose solutions showed a shear thinning behavior over the shear rate at temperature from 80 to 120°C. The zero shear viscosity (η_o) was obtained by using the simplified Cross model to fit experimental data. The η_o values were used for detailed viscosity‐concentration and activation energy analysis. The exponent in the viscosity‐concentration power law was found to be 3.63 at 80°C, which is comparable with cellulose dissolved in other solvents, and to be 5.14 at 120°C. The activation energy of the cellulose solution dropped from 70.41 to 30.54 kJ/mol with an increase of concentration from 10 to 25 wt %. The effects of temperature and concentration on the storage modulus (G′), the loss modulus (G″) and the first normal stress difference (N₁) were also analyzed in this study. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Use of 1‐hexyl‐3‐methylimidazolium bromide ionic liquid in the recovery of lactic acid from wine

BACKGROUND: Lactic acid has many different applications in a variety of industries including the food, cosmetics, packaging, leather and chemical industries. Current methodologies for lactic acid production are lengthy and complicated and more efficient methods are being sought. Some organic wastes contain lactic acid and our work investigates the use of ionic liquids (ILs) in the efficient and selective extraction of lactic acid from organic waste using wine as a model system. The ionic liquid was chosen based on its ability to selectively solvate and separate lactic acid from the remaining bulk waste material. RESULTS: Several ILs including 1‐hexyl‐3‐methylimidazolium chloride (hmimCl), 1‐hexyl‐3‐methylimidazolium bromide (hmimBr), 1‐hexyl‐3‐methylimidazolium iodide (hmimI) and N‐hexylpyridinium iodide (hpyrI) have been synthesized in high yield (68‐95%) using microwave technology. Lactic acid is soluble in each of the ILs synthesized with optimum results achieved with hmimBr where lactic acid is miscible in all proportions. HmimBr has been used to successfully separate and extract lactic acid from wine as confirmed by FTIR spectroscopy. Furthermore, it has been possible to recover the IL for recycle in subsequent extraction cycles where the efficiency for the extraction process increases with each recycle. CONCLUSION: HmimBr has been used for the first time in a novel process for the separation and recovery of lactic acid from wine, as confirmed by FTIR spectroscopy. This work demonstrates a novel process which can be applied to the recovery of lactic acid from organic waste. Copyright © 2012 Society of Chemical Industry     

Mild condition dissolution of high molecular weight cotton cellulose in 1‐butyl‐3‐methylimidazolium acetate/N,N‐dimethylacetamide solvent system

To investigate the effective dissolution of high molecular weight (MW) cellulose macromolecules at ambient conditions, cellulose (DP > 4,000) derived from cotton fiber waste was dissolved in 1‐butyl‐3‐methylimidazolium acetate (BMIMAc)/N,N‐dimethylacetamide (DMAc) solvent in this study. High MW cotton cellulose achieves a solubility between 3% and 5% cellulose concentrations using BMIMAc/DMAc solvent at ambient conditions. Rheological studies showed that all cellulose/solvent solutions displayed a shear thinning behavior. Results from the physical characterization revealed that well‐dissolved cotton cellulose exhibited highly porous structure and the crystalline structure of cotton cellulose was highly disrupted during dissolution and regeneration processes. This study is the first to report on the ability of BMIMAc/DMAc solvent system to dissolve high MW cellulose under ambient conditions, which represents an energy‐saving and environmentally friendly approach. As cellulose used in this study was derived from low quality waste cotton fibers, the potential utilization of such cotton cellulose may create a competitive market for low quality cotton and target advanced applications of cellulose‐based products for green materials and energy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45928.