Dissolved In N,N-dimethylacetamide Research Articles

"CELLULOSE HYDROGEL FIBRE FROM NIPA PALM (NYPA FRUTICANS) SHELL USED FOR ADSORPTION OF METHYLENE BLUE FROM WASTEWATER "

Cellulose was chemically extracted from nipa palm (Nypa fruticans) shell, which was used to prepare hydrogel fibre and applied as an environment-friendly adsorbent for methylene blue. The purified cellulose was dissolved in N,N-dimethylacetamide (DMAc), with the addition of 6% lithium chloride (LiCl), at room temperature for 5 days. Then, the cellulose solution was coagulated by the phase inversion process under ethanol vapor to obtain cellulose hydrogel fibre. The adsorption results showed that when the initial concentration of the methylene blue solution was increased from 20 to 100 mg/L at pH 10, the adsorption capacity also rose from 3 to 11.53 mg/g after 15-minute immersion. In addition, the equilibrium adsorption isotherm was well-fitted to the Langmuir isotherm model and the maximum adsorbed amount was 13.23 mg/g. Furthermore, the cellulose hydrogel fibre showed high reusability, as the removal efficiency of methylene blue remained at a level of approximately 80% after five recycles.

Pursuing the excision of carbon-centred hexanuclear scandium clusters {CSc

A multi-gram synthetic route to black solid {CSc6}I12Sc (1) was developed which comprises the reaction of scandium triiodide, ScI3, with graphite and scandium metal at 850°C. Compound 1 dissolved in N,N-dimethylacetamide (DMA) to form a red solution. Results derived from 45Sc NMR and EPR spectroscopy indicated that a scandium cluster species exists in this solution along with a complex cation [Sc(DMA)6]3+. From these solutions crystals of [Sc(DMA)6]I3 (2) and a red oily product was isolated. Compound 2 was also prepared independently by dissolving ScI3 in DMA and two polymorphs, orthorhombic 2O and monoclinic 2M were crystallised. {CSc6}I12Sc (1) also dissolved in THF yielding a red solution which contains [ScI6]3− and a scandium cluster species, as analysed by 45Sc NMR and EPR spectroscopy.

Polyvinylidene Fluoride Membrane with a Polyvinylpyrrolidone Additive for Tofu Industrial Wastewater Treatment in Combination with the Coagulation-Flocculation Process.

Wastewater from the tofu industry contains many pollutants that are very harmful to the environment, significantly endangering aquatic life and producing a pungent odor. This study aims to prepare a polyvinylidene fluoride (PVDF) membrane with the additive polyvinylpyrrolidone (PVP), and utilize it to treat tofu wastewater in the ultrafiltration (UF) process. Flat sheet membranes were prepared using PVDF that was dissolved in N,N-dimethylacetamide (DMAc) and then combined with the additive material of PVP at the varying compositions of 14.9/0.1, 14.85/0.15, and 14.8/0.2 g of PVDF/gram of PVP. The addition of PVP was proposed to improve the properties of the membranes. Characterization by scanning electron microscope (SEM), water contact angle, and Fourier transform infrared spectroscopy (FTIR) were performed on the PVDF/PVP membrane flat sheet in order to understand and compare changes in the physical and chemical properties that occurred in the membrane. Prior to the UF process, the tofu wastewater was treated by a coagulation–flocculation process through a jar tester using poly aluminum chloride (PAC) as a coagulant. Based on the membrane characterization, the addition of PVP improved the physical and chemical properties of membranes. The pore size of the membrane becomes larger, which could increase permeability as well as the flux value. The TSS and turbidity of the water produced in the UF process decreased with an increase in feed pressure due to a greater driving force generated to facilitate the penetration of the suspended solids. The UF results showed that the effect of PVP on water flux was greatest for the 14.85/0.15 PVDF/PVP membrane for both pure and wastewater. In addition, the highest percentage of rejection for TSS and turbidity were observed in the 14.9/0.1 PVDF/PVP membrane and rejection for TDS was indicated in the 14.8/0.2 PVDF/PVP membrane. Meanwhile, the resulting pH decreased slightly across all samples as feed pressure increased.

Chitin Hydrogels Prepared at Various Lithium Chloride/N,N-Dimethylacetamide Solutions by Water Vapor-Induced Phase Inversion

Chitin was chemically extracted from crab shells and then dissolved in N,N-dimethylacetamide (DMAc) solvent with lithium chloride (LiCl) at 3, 5, 7, and 10%. The concentrated chitin-DMAc/LiCl solutions were used for the preparation of chitin hydrogels by water vapor-induced phase inversion at 20°C. The coagulation process was investigated while altering the concentration of LiCl in the DMAc solution. The shear viscosity of the chitin solution increased with higher LiCl amounts and decreased when the concentration of LiCl was reduced by adding water to the chitin solution, implying high LiCl concentration delayed the coagulation of chitin solution in the presence of water. The viscoelasticity of the chitin solutions indicated the gel formation intensification was dependent on the dose of LiCl and chitin in the DMAc solution. After the chitin solution was coagulated, the resultant hydrogels had water contents of 387–461% and the tensile strength varied from 285 to 400 kPa when the concentration of LiCl in the hydrogel was adjusted to 3% and 7%, respectively. As for viscoelasticity, the complex modulus of the chitin hydrogels indicated that the increment of the LiCl concentration up to 7% formed the tight hydrogels. Atomic force microscopic (AFM) image revealed the formation of the entanglement network and larger domains of the aggregated chitin segments. However, the hydrogel prepared at 10% LiCl in DMAc solution exhibited weak mechanical properties due to the loose hydrogel networking caused by the strong aggregation of the chitin segments.

Fabrication of regenerated cellulose films by DMAc dissolution using parenchyma cells via low-temperature pulping from Yunnan-endemic bamboos

In this study, regenerated cellulose (RC) thin films were obtained using parenchyma cellulose from large clustered bamboos which were endemic to Xishuangbanna area in Yunnan province, China. The bamboo parenchyma cells were separated from their low-temperature (140 ℃ of the maximum temperature) kraft pulps through multi-screening. The cellulose was dissolved in N,N-dimethyl acetamide (DMAc) solvent with LiCl amount from 6 % to 10 %, then regenerated in the glycerol-water solution. X-ray diffraction analysis indicated the crystalline forms of RC films were transited from cellulose I to cellulose II. TGA analysis suggested that lower LiCl usage take an advantage on the higher thermal stability of the RC films. The DMAc-related solvent with a relatively lower LiCl dosage displayed a stronger capacity of cellulose dissolution, shed light on its considerable industrial application prospects and facilitated the high value-added utilization of waste biomass resources.

Enhancement of Flame Retardancy of Colorless and Transparent Semi-Alicyclic Polyimide Film from Hydrogenated-BPDA and 4,4'-oxydianiline via the Incorporation of Phosphazene Oligomer.

Enhancement of flame retardancy of a colorless and transparent semi-alicyclic polyimide (PI) film was carried out by the incorporation of phosphazene (PPZ) flame retardant (FR). For this purpose, PI-1 matrix was first synthesized from hydrogenated 3,3′,4,4′-biphenyltetracarboxylic dianhydride (HBPDA) and 4,4′-oxydianiline (ODA). The soluble PI-1 resin was dissolved in N,N-dimethylacetamide (DMAc) to afford the PI-1 solution, which was then physically blended with PPZ FR with the loading amounts in the range of 0–25 wt.%. The PPZ FR exhibited good miscibility with the PI-1 matrix when its proportion was lower than 10 wt.% in the composite films. PI-3 composite film with the PPZ loading of 10 wt.% showed an optical transmittance of 75% at the wavelength of 450 nm with a thickness of 50 μm. More importantly, PI-3 exhibited a flame retardancy class of UL 94 VTM-0 and reduced total heat release (THR), heat release rate (HRR), smoke production rate (SPR), and rate of smoke release (RSR) values during combustion compared with the original PI-1 film. In addition, PI-3 film had a limiting oxygen index (LOI) of 30.9%, which is much higher than that of PI-1 matrix (LOI: 20.1%). Finally, incorporation of PPZ FR decreased the thermal stability of the PI films. The 10% weight loss temperature (T10%) and the glass transition temperature (Tg) of the PI-3 film were 411.6 °C and 227.4 °C, respectively, which were lower than those of the PI-1 matrix (T10%: 487.3 °C; Tg: 260.6 °C)

Acetylation of Nata de coco (bacterial cellulose) and membrane formation

Nata de coco (NDC), a bacterial cellulose formed by Acetobacter xylinum, was utilized to fabricate a membrane via acetylation and phase inversion methods. The NDC was activated and dissolved in N,N-Dimethylacetamide (DMAc) with lithium chloride (LiCl) at varying amounts of NDC, LiCl/DMAc ratio, activation temperature, and dissolution temperature. Acetylation was done by adding acetic anhydride (in a mass ratio of 1:12 NDC-anhydride) to NDC-DMAc/LiCl solution at a dissolution temperature of 110 °C for 3 hours. The modified-NDC was recovered via precipitation in methanol. The modified-NDC was washed with deionized water then freeze-dried. Modification was verified by determining the degree of substitution (DS) using titration and FTIR analysis. It was observed that the modification could be carried out at an NDC/DMAc (w/v) ratio of 1:75 at 120 °C for 1 hour, and addition of 8% (w/v) LiCl catalyst at 110 °C for 20 minutes. The DS of the modified-NDC was observed in the range of 2.84 – 3.69, which indicates a successful modification. This was further verified by the FTIR results. Membrane fabrication was carried out using the modified-NDC via immersion-precipitation and solvent evaporation methods. A successful membrane formation was observed using solvent evaporation.

Comparison between electrospun and Bubbfil-spun Polyether sulfone fibers

Electrospinning is a simple method for producing ultrafine fibers, and has attracted much recent interest. The classical approach was either polymer solutions or polymer melts. Bubbfil spinning (e.g. bubble-electrospinning) is a facile method to fabricate nanofibers with high surface area to volume ratio and high porosity. Polyether sulfone (PES) dissolved in N,N-Dimethylacetamide (DMAC) was used in this study to compare fiber morphologies of two technologies at the same spinning conditions. Effects of solution concentration, applied voltage and tip-to-collector distance on the morphology of the fibers were experimentally studied. It revealed that the Bubbfil spinning process is a better candidate for mass-production of nanofiber with controllable morphology.

Preferential Interactions between Lithium Chloride and Glucan Chains in N,N-Dimethylacetamide Drive Cellulose Dissolution

Naturally occurring cellulose is crystalline as a consequence of the strong interactions between the glucan chains that comprise it and therefore is insoluble in most solvents. One of the few solvent systems able to dissolve cellulose is lithium chloride (LiCl) dissolved in N,N-dimethylacetamide (DMA). By an integrated application of all-atom molecular dynamics (MD) simulations, reaction path optimization, free-energy calculations, and a force-matching analysis of coarse-grained atomistic simulations, we establish that DMA-mediated preferential interactions of Li(+) cations and Cl(-) anions with glucan chains enable cellulose dissolution in LiCl/DMA. The relatively weak solvation of Li(+), Cl(-), and glucan chains by DMA results in strong effective interactions of Li(+) and Cl(-) ions with the glucans, leading to cellulose dissolution. The small size of the Li(+) cations allows them to strongly couple to multiple interaction sites on the glucan chains of cellulose, including the spatially restricted regions around the ether linkages connecting neighboring glucose residues. Li(+) cations were thus identified as the main component responsible for driving cellulose dissolution. The mechanism for explaining the solubility of cellulose in the LiCl/DMA system deduced from the analysis of atomistic-scale simulations conducted in this work is also consistent with most of the empirical observations related to cellulose dissolution in salt/amide solvent systems.

Novel GO-blended PVDF ultrafiltration membranes

Using the immersion phase inversion process, polyvinylidene fluoride (PVDF) and graphene oxide (GO) dissolved in N, N-dimethylacetamide (DMAc) were combined to prepare organic–inorganic-blended ultrafiltration membranes. The prepared GO-blended PVDF membranes were characterized by several analytical methods, such as Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), contact angle measurements and permeation tests. Owing to the hydrophilic nature of GO, the GO-blended PVDF membranes appeared to be more hydrophilic and have higher pure water fluxes recovery ratio than the unblended PVDF membranes. The beneficial effects of adding GO to the PVDF membrane, in terms of mechanical strength, permeation properties, and anti-fouling performance, were also examined. The results show that, when the content of GO added in the casting solution was 0.20wt.%, the properties and structure of the blended membranes can be improved obviously. The permeability of the blended membrane increases by 96.4% with a slight change of retention; the tensile strength increases by 123%. Moreover, the contact angle decreases from 79.2° to 60.7°, which implies that the anti-fouling ability of the membrane is improved.

Preparation and characterization of all para‐position polysulfonamide fiber

AbstractPoly(4,4′‐diphenylsulfone terephthalamide) referred to as all para‐position polysulfonamide (all para‐position PSA) is a special kind of PSAs, copolymers of 3,3′‐diaminodiphenylsulfone, 4,4′‐diaminodiphenylsulfone, and terephthaloyl chloride. However, with the increasing para‐structure content in the PSAs, the PSA shows very poor solubility in common amide‐type polar aprotic solvents and cannot be used for wet spinning. In this article, it was found that all para‐position PSA can be easily dissolved in N,N‐Dimethylacetamide (DMAc)/LiCl system, and then the all para‐position PSA fiber was prepared for the first time by wet spinning. The properties of all para‐position PSA pulps and fibers were investigated via Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy, thermal gravimetric analysis, dynamical mechanical analysis, X‐ray diffraction (XRD), and tensile strength testing. The tensile strength, elongation at break, and crystallinity of the resulting fiber were 4.4 cN/dtex, 15.9%, and 33.53%, respectively. The results indicated that all para‐position PSA fiber was a high‐temperature resistance fiber with better mechanical properties than common PSA fiber. The improved tensile strength of the fiber will expand its applications and may take place of Nomex in certain fields and become a new generation of flame retardant and high‐temperature resistant material. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Antimicrobial m-Aramid Nanofibrous Membrane for Nonpressure Driven Filtration

An antimicrobial nanofibrous membrane for nonpressure driven filtration is reported. m-Aramid as an N-halamine precursor was dissolved in N,N-dimethylacetamide (DMAc), and the m-aramid nanofibrous membrane was formed using an electro-spinning process. The morphology of the m-aramid membrane was analyzed by scanning electron microscopy (SEM), and the mean pore size, pore size distribution and liquid permeability of the m-aramid membrane were determined using a capillary flow porometer. The antimicrobial efficacy of the m-aramid membrane was performed by nonpressure driven filtration. The chlorinated m-aramid membrane showed excellent antimicrobial activity against Escherichia coli and Staphylococcus aureus. The chlorine lost after filtration could be regained upon rechlorination.

Effect of Dodeca-Tungstophosphoric Acid on Morphology and Performance of Polyethersulfone Membrane for Gas Separation

In the present paper, organic/inorganic membrane has been prepared for gas separation by incorporating heteropolyacids (HPA) such as 12-phosphotungstic acid (PWA) into the base polymer. Flat-sheet membranes were prepared using polyethersulfone (PES) dissolved in N, N-dimethylacetamide (DMAc) with and without the addition of PWA. The membranes were prepared from quaternary (PES/PWA/DMAc/water) and ternary (PES/PWA/DMAc) systems by wet and dry (solvent evaporation) techniques. Composite membranes were produced via a two-stage wet phase inversion method. The skin layer was synthesized from ternary (PVA/PWA/H 2 O) system on the surface of PES membrane as the sub layer, using dip coating technique. The permeability and selectivity of H 2 , N 2 , O 2 and air were tested. In dry method, the porosity of the prepared membrane was slightly increased by addition of PWA. The increased porosity results in flux improvement. By increasing the concentration of PWA in the wet procedure, the channel-like structure appeared. The presence of PWA in the casting solution results in lower flux for O 2 gas and higher selectivity for H 2 /O 2 pair.

Effects of dilution with PMMA and network formation on fluorescence from benzimidazolylphenylenes linked to PMMA network

AbstractN,N′‐5‐(2‐benzimidazolyl)‐1,3‐phenylenebis(methacrylamide) (BIPBMA) was synthesized and copolymerized with methyl methacrylate (MMA) by changing feed BIPBMA/MMA molar ratio. The swelling experiments suggest that these cross‐linked copolymers (c‐copolymers) have a polymer network structure. To compare with c‐copolymers, synthesized 3‐(2‐benzimidazolyl) phenylmethacrylamide (BIPMA) was copolymerized with MMA by changing feed BIPMA/MMA molar ratio. These linear copolymers (l‐copolymers) were dissolved in N,N‐dimethylacetamide (DMA). The fluorescence spectra of c‐copolymers were well fitted by trial‐and‐error contraction with sums of five or less of Lorentzian equations. The fluorescence spectra of l‐copolymers were so distributed that only the initial peak was fitted to a single Lorentzian equation. The fluorescence spectra of BIPBMA/DMA solutions with various concentrations were also fitted to sums of five or less of Lorentzian equations. The fitted coefficients were used to quantify dilution effect. The fluorescence intensity of c‐copolymers is higher than that of l‐copolymers in a same chromophore concentration. A relation between the intensity and the chromophore concentration shows a concentration quenching owing to chromophore aggregating for c‐copolymer, l‐copolymer, and the solution. A critical concentration point before which the intensity increases appeared in the plots of intensity against concentration for the c‐copolymer and the solution. The critical point of the c‐copolymer is higher than that of the solution and that of the l‐copolymer (if observed). This suggests that the network formation and the dilution break up the chromophore aggregates. The fluorescence spectra of c‐copolymers (1/200) adjusted by varying AIBN concentrations suggest that the fluorescence is independent of the extent of cross‐linking. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

M-Aramid Films in Diverse Coagulants

m-Aramid dissolved in N,N-dimethylacetamide (DMAc), were coagulated in different coagulants such as water, methanol, ethanol, propanol and butanol. Various concentrations and temperatures of the coagulants were also used to evaluate dyeing properties of coagulated m-aramid films. Field emission scanning electron microscopy (FE-SEM) was employed to investigate the surface morphology of m-aramid films. Wide angle X-ray diffraction (WAXD) was conducted in order to measure crystallinity change of mcaramid fibers and films. WAXD patterns showed that crystallinity of m-aramid fibers was reduced after film formation. In addition, color depth (K/S value) was measured and the results revealed that the film coagulated in water possessed fairly enhanced color depth.

Nanocomposite Membranes Made from Sulfonated Poly(ether ether ketone) and Montmorillonite Clay for Fuel Cell Applications

Poly(ether ether ketone) (PEEK) was sulfonated at various degrees with sulfuric acid and dissolved in N, N-dimethylacetamide (DMAc). Montmorillonite (MMT) clay was mixed with this solution and solv...

Synthesis of polypeptides from activated urethane derivatives of α‐amino acids

AbstractA series of activated urethane‐type derivatives of α‐amino acids were synthesized and applied to polypeptide synthesis. The urethane used herein, N‐(4‐nitrophenoxycarbonyl)‐α‐amino acids 1, were synthesized by N‐carbamoylation of γ‐benzyl‐L‐glutamate, β‐benzyl‐L‐aspartate, L‐leucine, L‐phenylalanine, and L‐proline, with 4‐nitrophenyl chloroformate. When 1 was dissolved in N,N‐dimethylacetamide (DMAc) and heated at 60 °C, it was smoothly converted into the corresponding polypeptides with releasing 4‐nitrophenol and carbon dioxide. Spectroscopic analyses of the obtained polypeptides revealed that they were comparable with the authentic polypeptides synthesized by the ring‐opening polymerizations of amino acid N‐carboxyanhydrides (NCAs). Besides the successful polycondensations of a series of 1, their polycondensations of 1a and other 1 were also successfully carried out to obtain the corresponding statistic copolypeptides. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2525–2535, 2008

Silylation of Cellulose and Starch – Selectivity, Structure Analysis, and Subsequent Reactions

The silylation of cellulose and starch under different starting conditions is reviewed. The control of the degree of substitution (DS) and regioselectivity in dependence of the reaction pathway are discussed in detail. The synthesis of trimethylsilyl cellulose (TMSC) in the system hexamethyldisilazane (HMDS)/ammonia leads to partially and completely silylated products controlled by the amount of the components. Hydrolytic desilylation of TMSC in tetrahydrofuran (THF)/ammonia gives the partially desilylated products. The desilylation proceeds statistically along the polymer chains. The reaction of cellulose dissolved in N,N-dimethylacetamide (DMA)/LiCl with bulky thexyldimethylchlorosilane (TDSCl) in the presence of imidazole leads to 2,6-di-O-TDS cellulose. The silylation of starch dissolved in dimethylsulfoxide (DMSO) with TDSCl/pyridine results in the formation of regioselectively 2-O and 6-O functionalized silyl ethers with DS values up to 1.8. 6-O Silyl ethers of cellulose and starch were synthesized with TDSCl highly activated in the reaction system N-methylpyrrolidone (NMP)/ammonia. Two- dimensional NMR techniques after subsequent modifications of the remaining OH groups have been established as important methods for the characterization of the substitution pattern of the described silyl ethers. In the case of starch, the distribution of the substituents could be detected not only in the anhydroglucose units (AGU) but also in the non-reducing end groups (NEG).

Low Dose High Resolution Electron Microscopy (HREM) Analysis of Regularly Twisted Poly(m-Phenylene Diisophthalamide) (MPDI) Fibers

Abstract Poly(m-phenylene diisophthalamide) (MPDI) is an all-aromatic polyamide used to manufacture thermally stable high strength fibers (Nomex® by DuPont). The X-ray diffraction data of the commercial solution-spun fiber is in good agreement with a triclinic unit cell structure proposed by Kakida et al. with hydrogen bonds forming a two dimensional network approximately orthogonal to the polymer main chain. When MPDI dissolved in N,N-dimethylacetamide (DMAc) is crystallized over several weeks by exposure to a non-solvent (water) in a diffusion vessel, the polymer precipitates into uniform, regularly twisted crystalline bundles (Figure 1). TEM images show that the bundles consist of 1-8 individual strands and can reach a length of 20 microns. The pitch and the diameter of these bundles are uniform along the visible length for each bundle but depend on the number of strands per bundle. The diameter of an individual strand is 20-50 nm resulting in a diameter of 20-300 nm for a bundle and a “macroscopic” pitch of 200-1000 nm (Figure 2).

Nematogenic aromatic block copolymers of rigid and flexible units. II. Phase equilibria

AbstractThe solubility and mesophase behavior are investigated for block copolymers of poly(p‐benzamide) (PBA), the polyterephthalamide of p‐aminobenzhydrazide (PABH‐T), and PBA and poly(m‐phenylene isophthalamide) (MPD‐I) dissolved in N,N‐dimethylacetamide (DMAc) containing 3% LiCl. The block copolymers, whose synthesis and characterization were described in the previous paper in this series, included samples prepared by the two‐step and multistep copolycondensations. The first of these methods yields a considerable amount of the flexible homopolymer (PABH‐T) and also some of the rigid homopolymer. The flexible homopolymer can be removed from the block copolymer by extraction with dimethyl sulfoxide (DMSO), whereas precipitation may offer a way to remove the rigid homopolymer. The results observed for the block copolymers are compared with those for the homopolymers and mixtures of homopolymers. The apparent solubility of the PBA/PABH‐T block copolymers obtained by the two‐step method is unusually large but decreases toward the value observed for mixtures after the flexible homopolymer had been extracted with DMSO. Labile adducts involving PABH‐T and/or the block copolymer appear to be capable of forming a single mesophase. This offers a most interesting approach to the preparation of composite materials involving rigid and flexible polymers.