Cellulose Carbamate Research Articles

Synthesis of Novel Cellulose Carbamates Possessing Terminal Amino Groups and Their Bioactivity

Cellulose phenyl carbonates are an excellent platform to synthesize a broad variety of soluble and functional cellulose carbamates. In this study, the synthesis of cellulose carbamates with terminal amino groups, namely ω-aminoethylcellulose- and ω-aminoethyl-p-aminobenzyl-cellulose carbamate, is discussed. The products are well soluble and their structures can be clearly described by NMR spectroscopy. The cellulose carbamates exhibit a bactericide and fungicide activity in vitro. The ω-aminoethylcellulose carbamate possesses a strong activity against Candida albicans and Staphylococcus aureus (IC50 of 0.02 mg mL(-1) and 0.05 mg mL(-1)). The antimicrobial activity and cytotoxicity can be improved by p-amino-benzylamine (ABA) as an additional substituent. The mixed cellulose carbamate exhibits a high biocompatibility (LC50 of 3.18 mg mL(-1)) and forms films on cotton and PES, which exhibit a strong activity against S. aureus and Klebsiella pneumoniae.

Synthesis of kenaf cellulose carbamate and its smart electric stimuli-response

Cellulose carbamate (CC) was produced from kenaf core pulp (KCP) via a microwave reactor-assisted method. The formation of CC was confirmed by Fourier transform infrared spectroscopy and nitrogen content analysis. The degree of substitution, zeta potential and size distribution of CC were also determined. The CC was characterized with scanning electron microscopy, X-ray diffraction and thermogravimetry analysis. The CC particles were then dispersed in silicone oil to prepare CC-based anhydrous electric stimuli-responsive electrorheological (ER) fluids. Rhelogical measurement was carried out using rotational rheometer with a high voltage generator in both steady and oscillatory shear modes to examine the effect of electric field strength on the ER characteristics. The results showed that the increase in electric field strength has enhanced the ER properties of CC-based ER fluid due to the chain formation induced by electric polarization among the particles.

Physico-mechanical properties of a microwave-irradiated kenaf carbamate/graphene oxide membrane

Cellulose carbamate (CC) prepared using microwave irradiation was reinforced with graphene oxide (GO) to fabricate homogeneous and highly ordered CC–GO membranes using a simple solution-mixing method. The effect of GO content on the properties of the membranes was investigated. Atomic force microscope and transmission electron microscope images indicated that the self-synthesized GO nanosheets exhibited exfoliated layers within the CC. X-ray diffraction results confirmed the crystalline structure of cellulose I and cellulose II in the CC pulp and CC–GO membranes, respectively. Increasing the GO content from 0 to 4 wt% resulted in a slight decrement in the crystallinity index. The membrane containing 4 wt% GO possessed a tensile modulus and strength higher by approximately 525 and 93 %, respectively, compared to the neat CC. Thermogravimetric analysis proved that the GO promoted higher thermal stability and carbon yields. The 3D homogeneous porous structures of the CC–GO membranes were viewed under a field emission scanning electron microscope. These improvements in the membrane properties were confirmed by Fourier transform infrared spectroscopy and are attributed to the strong and effective interactions between CC and GO.

Improved Synthesis of Cellulose Carbamates with Minimum Urea Based on an Easy Scale-up Method

Cellulose carbamates (CCs) were successfully prepared from cellulose/urea (CU) mixtures based on an easy scale-up method and minimum urea. Urea content and the reaction conditions on the nitrogen content of the reacted CU (RCU) mixtures and CCs were systematically investigated. RCU mixtures and CCs were characterized with elemental analysis, Fourier transform infrared spectroscopy, X-ray diffraction, NMR spectrometry and solubility testing. The result indicated that almost all of urea was involved in the derivatization reaction and cellulose was converted into CC with absence of byproducts. The nitrogen content of CCs increased with an increase of the urea content and the reaction temperature, as well as the reaction time. CCs retained the cellulose I crystalline, and the degree of polymerization hardly changed with the reaction conditions. CCs prepared from CU mixtures with the urea content of 3.4–4.6 wt % displayed good solubility in NaOH/ZnO aqueous solutions. Especially, RCU mixtures without washing c...

Nanoparticle Formulation of AEA and BAEA Cellulose Carbamates Increases Biocompatibility and Antimicrobial Activity.

Antimicrobially active polymers with a cationic moiety gain increasing interest in health care providing a biocompatible alternative to commonly used products. They adhere to the polyanionic bacterial surface, disrupt cell membranes and kill bacteria. An efficient path to obtain amino group-containing cellulose is nucleophilic displacement reaction of p-toluenesulfonic acid ester and amines leading to 6-deoxy-6-(ω-aminoalkyl) aminocellulose carbamates. Spherical nanoparticles of the obtained 6-deoxy-6-(2-aminoethyl) amino (AEA) and 6-deoxy-6-{2-bis[N',N'-(2-aminoethyl)]aminoethyl}amino (BAEA) cellulose carbamate with a size range of 80-120 nm were produced. The AEA and BAEA cellulose carbamates exhibited significant antimicrobial activity with moderate cell compatibility. Nanoparticle formulation enhanced biocompatibility.

Cellulose carbonates: a platform for promising biopolymer derivatives with multifunctional capabilities.

Cellulose carbonates as a platform compound open new possibilities for the design of advanced materials based on the most important renewable resource cellulose. In the present feature, the chemistry of cellulose carbonates is discussed considering own research results adequately. After a short overview about methods for activation of polysaccharides for a conversion with nucleophilic compounds in particular with amines, details about various methods for the synthesis of polysaccharide carbonates are discussed. The main issue of the feature is the synthesis and aminolysis of cellulose carbonates with low, intermediate, and high degree of substitution and the evaluation of this chemistry with respect to specific challenges. Functional cellulose carbamates, obtained from cellulose phenyl carbonate by aminolysis, show the potential use of this class of celluloses. Immunoassays and zwitterionic polymers are included as representative examples regarding properties and application of the new cellulose-based products.

Structure and Properties of Regenerated Cellulose Filaments Prepared from Cellulose Carbamate–NaOH/ZnO Aqueous Solution

In this work, regenerated cellulose (RC) filaments were successfully spun from cellulose carbamate in a NaOH/ZnO aqueous solution on a pilot scale. The structure and properties of the RC filaments were characterized using SEM, FT-IR, elemental analysis, 13C NMR, XRD, 2D WAXD, tensile testing, and dye testing. The nitrogen-free and sulfur-free RC filaments exhibited a bright surface and circular cross section. The filaments demonstrated a typical cellulose II crystal structure and a relatively high degree of orientation. Improved tenacity and structure were obtained in the RC fibers due to improved post-processing spinning steps and an increased drawing ratio. The tenacity of the fibers was determined in the range of 1.69–2.36 cN/dtex, which was comparable with that of commercial viscose rayon. Furthermore, the RC filaments showed improved dye properties compared with viscose rayon. The described carbamate pathway provided a simple and environmentally friendly method, offering an alternate to the environmental drawbacks of the viscose process.

Green Method for Production of Cellulose Multifilament from Cellulose Carbamate on a Pilot Scale

In the cellulose industry, the viscose process is still occupying the leading position, although this process generates several environmentally hazardous byproducts. Here we report a novel method for the production of cellulose multifilament from cellulose carbamate (CC) on a pilot scale. In this method, CC was first prepared efficiently by microwave heating; it was then dissolved in NaOH/ZnO aqueous solutions through a freezing–thawing process. Wet spinning of the CC solution was performed on a pilot-scale machine. The cellulose multifilament displayed a dense circular microstructure and excellent physicochemical properties. The tensile strength and elongation at break of the multifilament in dry state were 2.58 cN/dtex and 12.1%, respectively. Moreover, the process could utilize most of the conventional equipment for the viscose method, which could have a great impact on the current cellulose industries.

Insights into chromatographic enantiomeric separation of allenes on cellulose carbamate stationary phase

Allenes are cumulenes with three contiguous carbons linked together through double bonds. 1,3-disubstituted allenes are not superimposable on their mirror image; as a consequence they are chiral. Chiral allenes are increasingly important in organic synthesis due to their interesting reactivity. Because of their applications in the field of asymmetric catalysis and in the pharmaceutical industry their optical purity is always a parameter which needs to be determined. In this article, we report the enantiomeric separation of hexa-3,4-diene-3-ylbenzene, an aromatic allene, on a cellulose carbamate (Chiralcel OD-3) stationary phase, using heptane as the mobile phase. Spectroscopic studies using infrared (IR) and vibrational circular dichroism revealed that, in the presence of heptane, the stationary phase undergoes a conformational change due to intermolecular H-bonding between the CO and NH of the neighboring polymer chains. Van’t Hoff plots for the retention factor, k, showed that the retention of the two enantiomers is dominated by the enthalpy, while the plot for the selectivity, α, is entropy driven. This suggests that the enantioselectivity is a result of inclusion of the enantiomers in the cavities of the chrial stationary phase. VCD spectra, along with density functional theory calculation (DFT) of the interaction between each enantiomer and the chiral stationary phase, supported the chromatographic elution order findings.

Structure and properties of the regenerated cellulose membranes prepared from cellulose carbamate in NaOH/ZnO aqueous solution

Regenerated cellulose (RC) membranes were prepared from cellulose carbamate—NaOH/ZnO aqueous solutions by coagulating with H2SO4 solution. Structure, morphology and properties of the membranes were investigated by using scanning electron micrograph (SEM), X-ray diffraction, Fourier transform infrared spectroscopy, flow rate method, and tensile testing. The results from SEM and water permeability revealed that the pore size and water permeability of the membranes in wet state changed drastically as a function of the concentration of H2SO4 and coagulation temperature, whereas they hardly changed with the coagulation time. RC membranes coagulated with the relatively dilute H2SO4 solution at relatively low temperature exhibited better mechanical properties. This work provided a promising way to prepare cellulose membranes with different pore sizes and good physical properties.

Synthesis of kenaf cellulose carbamate using microwave irradiation for preparation of cellulose membrane

Cellulose carbamate (CCs) was produced from kenaf core pulp (KCP) using microwave reactor-assisted method. The effects of urea concentration and reaction time on the formation of nitrogen content in CCs were investigated. The CCs’ solubility in LiOH/urea system was determined and its membranes were characterized. As the urea content and reaction time increased, the nitrogen content form in CCs increased which enhanced the CCs’ solubility. The formation of CCs was confirmed by Fourier transform infrared spectroscopy (FT-IR) and nitrogen content analysis. The CCs’ morphology was examined using Scanning electron microscopy (SEM). The cellulose II and crystallinity index of the membranes were confirmed by X-ray diffraction (XRD). The pore size of the membrane displayed upward trend with respect to the urea content observed under Field emission scanning electron microscope (FESEM). This investigation provides a simple and efficient procedure of CCs determination which is useful in producing environmental friendly regenerated CCs.

Effect of graphene oxide on the solution rheology and the film structure and properties of cellulose carbamate

Highly ordered, homogeneous and reinforced cellulose carbamate (CC)/graphene oxide (GO) composite films were prepared using an easy, aqueous and solution-mixing method. The dynamic rheology measurement showed that the addition of 2wt.% GO decreased the complex viscosity of CC solution and significantly prolonged the valid spinning time of CC solution. X-ray diffraction characterization revealed that GO promoted the transition of crystalline structure of CC from cellulose I to II, and the addition of 2wt.% GO improved the orientation and crystallinity of the CC molecules. Scanning electron microscope images indicated that the GO layers were aligned parallel to the surface of the composite films. The incorporation of GO also showed profound effects on the macroscopic properties of the CC film. Compared to the pure CC, the composite showed a 280% increase in Young’s modulus and 180% increase in tensile strength by the addition of 2wt.% of GO. Moreover, the carbon yields of all the composite films were higher than that of pure CC film.

Preparation of cellulose and pulp carbamates through a reactive dissolution approach

Carbamoylation of various cellulosic materials was systematically studied, using a reactive dissolution approach. Reactions with cellulose, or pulp and aromatic isocyanates, were initiated as heterogeneous mixtures in hot pyridine. As the reaction proceeded, homogeneous solutions were obtained. However, attempts to synthesize highly substituted cellulose carbamates, with aliphatic isocyanates in pyridine, failed as homogeneous solutions were not achieved, even after long reaction times. Consequently, aliphatic cellulose carbamates were prepared via reactive dissolution in dimethylacetamide (DMA), with dibutyltin dilaurate (DBTL) as catalyst. Reactions of cellulose with aliphatic isocyanates in DMA/DBTL at elevated temperature also ended up as homogeneous solutions. The success of the carbamoylation reaction was assessed by means of FTIR, 1H, 13C, 31P and diffusion-ordered spectroscopy (DOSY) NMR. Carbamoylation of pre-hydrolysis hardwood kraft pulp (PHK), hardwood kraft pulp (HKP) and hemicellulose-poor hardwood kraft pulp (HPHKP) were also studied under similar conditions. Highly soluble carbamates were also obtained with the pulp derivatives. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) of the derivatives showed no significant improvement in the thermal properties compared with the untreated cellulose. However, DSC thermograms of some samples showed a phase change, which is attributed to a glass transition temperature (Tg). Also, a two-step decomposition process was observed in the TGA curves for the derivatives, which is attributed to the cleavage of carbamate substituents through a retro-carbamoylation and degradation of the cellulose backbone. Aromatic carbamates of cellulose showed similar molecular weight distributions compared to intact cellulose. However, for aliphatic cellulose carbamates the derivatization led to products with lower molecular weight.

Progress in cellulose shaping: 20 years industrial case studies at Fraunhofer IAP

Cellulose, the most abundant renewable organic material on earth, exhibits outstanding properties and useful applications, but also presents a tremendous challenge with regard to economical and environmentally friendly chemical processing. The viscose process, more than 100 year old is still the most widely utilized technology to manufacture regenerated cellulose fibers and films. Viscose fibers are produced today worldwide on a 5 million ton scale with various fiber types ranging from high performance tire yarn to textile filaments and staple fibers with excellent properties close to those of cotton. At Fraunhofer IAP, the technical equipment for viscose preparation, wet spinning of fibers, hollow fibers, and tube-like films is available on a min-plant scale. Research focused on raw materials testing, process optimization with regard to economic and ecological aspects, structural analysis of cellulose during processing, and structure–property relations of fibers and films. Similar to the viscose process, cellulosic fibers can be produced via cellulose carbamate as an environmentally friendly route. In a close cooperation of Fraunhofer IAP with industrial partners, a specific process based on cellulose carbamate was developed on a pilot plant scale, giving fiber properties close to those of conventional viscose fibers. In recent decades the N-methylmorpholine-N-oxide (NMMO)-technology turned out to be a nonderivatizing commercial alternative to the still dominant viscose route. From the very beginning, Fraunhofer IAP has been engaged in investigating the structure formation of cellulose fibers precipitated from NMMO-water solution, revealing structural reasons for the fibrillation tendency of these fibers and means to overcome them. Starting from fiber formation via dry-jet wet spinning, for the first time the blown film formation and the meltblown nonwovens technology were developed for cellulosics on a pilot plant scale at Fraunhofer IAP. Based on the elastic behavior of the dope at elevated temperatures, cellulose can be processed like a melt in the air-gap, offering new possibilities of shaping cellulose like meltable mass polymers. Combining cellulose carbamate with NMMO-monohydrate as a solvent, higher polymer concentrations in the dope and outstanding mechanical properties of the resulting fibers were achieved.

Preliminary Study on the Preparation of Bamboo Cellulose Carbamate

In this paper, bamboo fibers were utilized in synthesizing the cellulose carbamate (CC) together with urea for the first time. This paper explored the impact of a serious of factors on Nitrogen content of CC, including the concentration of sodium hydroxide solution used for activating, activation time, aging time, urea socking time, the concentration of urea solution, reaction time and reaction temperatures. Moreover, the analysis and characterizations of CC with different nitrogen contents were conducted by using FTIR, DSC, XRD and SEM. The result indicates that CC was generated as the cellulose reacted with urea, and the crystalline form of cellulose has changed after the esterification reaction. The surface morphology of fibers became wrinkle and rough after the reaction, thereby improving its solubility.

Preparation of Bonded Cellulose Tris(3,5-dimethylphenylcarbamate) Chiral Stationary Phases by Using Three Bifunctional Reagents

Three di-acyl chlolide reagents, adipoyl chloride, terephthaloyl chloride and isophthaloyl chloride, were used as spacer reagents to prepare bonded type of three cellulose (3,5-dimethylphenyl)carbamate (CDMPC) chiral stationary phases (CSPs). The CDMPC CSPs were prepared using these three acid chlorides as spacer agents at the 6-position of the primary hydroxyl group on the glucose unit of cellulose regioselectively. The chiral recognition ability of the prepared CSPs for five racemates was evaluated by normal-phase high-performance liquid chromatography (HPLC) with the following mobile phases: hexane/isopropanol (IPA), hexane/IPA/ tetrahydrofuran (THF) and hexane/IPA/chloroform. The result showed that these prepared CSPs can be used in THF and chloroform solutions and the chiral recognition abilities of the CSPs were improved depending on the eluents and chiral samples.

Preparation and Characterization of Cellulose Carbamate Regeneration Membrane by Supercritical Carbon Dioxide

The regenerated cellulose carbamate membranes were prepared by the phase inversion process. The structure and properties of the regenerated cellulose carbamate membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Besides, the effects of the casting solution concentration and the coagulation bath concentration on the mechanical property of regenerated cellulose carbamate membrane were discussed.

Synthesis and Characterization of Cellulose Carbamate from Wood Pulp, Assisted by Supercritical Carbon Dioxide

This paper considers the modification of wood-derived cellulose assisted by supercritical carbon dioxide (SC-CO2). Cellulose carbamate derivatives were successfully prepared from softwood pulp at 150 °C and 3000 psi for 6 hours. Compared with conventional methods, SC-CO2 was shown to be more efficient in the modification of wood-derived cellulose. The modified cellulose had a considerable increase in nitrogen content. During the characterization Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Thermogravimetry (TG), and Field Emission Scanning Electron Microscopy (FE-SEM) were employed to investigate the structural and morphological changes in modified cellulose from wood.

All-cellulose composites from woven fabrics

A method of creating all-cellulose composites from woven fabrics is introduced. Cellulosics when treated with mixtures of polyethylene glycol, urea and salt undergo carbamation. Cellulose carbamate is alkali-soluble. When the carbamated fabrics are immersed in alkali solutions and passed through pressure rolls, there is a limited dissolution of cellulose. On subsequent neutralization, the dissolved cellulose is regenerated as a matrix in the fabric and binds together the fibrous elements – thus creating a composite. In the paper we describe the process, characterize the composites, discuss advantages of the method and highlight challenges that remain to be addressed. The substrate is a woven fabric, but the method may be applied on other two-dimensional assemblies of cellulosic fibers such as non-wovens and paper.

Utilizing the Natural Fiber for Textile and Engineering

Copyright: © 2012 Chauhan A. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Nowadays, the whole world has focused its attention towards renewable and sustainable resources because of environment and health concerns. The development of new polymer from renewable raw materials in comparison to artificial fibers has increased during last few years. Natural fibers like pine needle, flax, jute and ramie are the most suitable reinforcement materials because of their relatively high strength and stiffness in industries such as automobile, packaging and construction materials due to economic and ecological aspects. Low cost, easily availability and required properties (viz. low density, mechanical properties) makes them attractive in place of glass, carbon and other synthetic fibers. The constituents of natural fibers are cellulose, hemicelluloses, lignin and pectins with a small quantity of the extractives. These natural fibers such as cellulose and silk are of tremendous use in textile industry. The properties of bio-fibers mainly depend upon their origin, age, climatic conditions and extraction techniques. The presence of hydroxyl groups (polar group) in various constituents of lingo-cellulosic fiber reduces the utilities in many applications. In order to improve its adhesion, various techniques like graft copolymerization, chemical treatment (viz. mercerization, acetylation, benzoylation etc.) and treatment with various coupling agent can be used. Graft copolymerization is an efficient technique to impart desirable properties to backbone polymers. Various workers have carried out the graft copolymerization onto different cellulosic backbone using vinyl monomers through various chemical and radiation techniques. Grafting of acrylate monomers individually and in binary mixtures onto cotton yarn by emulsion technique initiated by ceric ions has been widely studied. Graft copolymerization of methyl acrylate onto cellulose and thiolated holocellulose reported decrease in incorporation of graft in the latter. Graft copolymerization can be initiated by using chemical, ionic and radical initiator systems. Among these initiation systems the chemical initiation by grafting involving oxidizing agents such as potassium permanganate, potassium bromate, ceric ammonium nitrate, ozone hydroxyl radicals etc are promising from economic point of view. Different workers have studied the kinetics of graft copolymerization of vinyl monomers onto the starch and synthetic copolymers but few attempts seems to have been made to study kinetics of graft copolymerization of vinyl monomers onto natural fibers. Graft copolymerization of acrylic monomers onto cotton fabric using an activated cellulose thiocarbonate–azobis-isobutyronitrile redox system has been investigated and it has been found that a reaction medium of pH 2.0 and temperature of 70°C constituted the optimum conditions for grafting. Methyl Meth Acrylate (MMA) has been found to be superior than other monomers. Chemically modified cellulosic depicts higher grafting with MMA as compared to unmodified cellulose. Oxidized cellulose was grafted with 2-methyl-5-vinyl pyridine using a H2O2-thioureadioxide redox system. Considerable grafting took place on oxidized cellulose on excluding thio-ureadioxide from the system whereas it offsets grafting onto cotton cellulose. Grafting of MMA onto modified cellulose at 60°C using peroxydiphosphate as an initiator, they determined the rate of grafting by varying initiator, monomer, nature of the substrate and temperature. MMA was graft copolymerized onto cotton-cellulose using hexavalent chromium, Cr (VI) as an initiator. Graft copolymers were subjected to various chemical, mechanical and thermal evaluation and the results showed that there has been a significant improvement in properties. Graft copolymerization of styrene onto cellulose was investigated under variable reaction conditions using H2O2 as an initiator. Cellulose carbamates having less than 1.1% nitrogen showed lower graft yield than the unmodified cellulose. Styrene was graft copolymerized onto cellulose in the form of cotton linters, cotton cloth and rayon by ionizing radiation. The graft copolymers thus obtained were characterized by removing the cellulose back-bone on hydrolysis and determining the molecular weights of the residual poly (styrene). Graft copolymerization has been widely studied using various vinyl monomers by different techniques and has improved various properties of the fiber. With the advancement of science and technology there are numerous advanced techniques like SEM, AFM, TEM, XRD, FTIR, DSC, TGA, DTA that can evaluate various morphological, physicochemico-thermal change in fiber.