Binding cellulose and chitosan via click chemistry: Synthesis,characterization, and formation of some hollow tubes

A novel cellulose‐click‐chitosan polymer was prepared successfully in three steps: (1) propargyl cellulose with degrees of substitution (DS) from 0.25 to 1.24 was synthesized by etherification of bamboo Phyllostachys bambusoide cellulose with propargyl chloride in DMA/LiCl in the presence of NaH. The regioselectivity of propargylation on anhydrous glucose unit determined by GC‐MS was in the order of 2 >> 6 > 3; (2) the functional azide groups were introduced onto the chitosan chains by reacting chitosan with 4‐azidobenzoic acid in [Amim]Cl/DMF and the DS ranged from 0.02 to 0.46; (3) thus, the cellulose‐click‐chitosan polymer was obtained via click reaction, that is, the Cu(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction, between the terminal alkyne groups of cellulose and the azide groups on the chitosan backbone at room temperature. The successful binding of cellulose and chitosan was confirmed and characterized by FTIR and CP/MAS ¹³C NMR spectroscopy. TGA analyses indicated that the cellulose‐click‐chitosan polymer had a higher thermal stability than that of cellulose and chitosan as well as cellulose–chitosan complex. More interestingly, some hollow tubes with near millimeter length were also observed by SEM. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Immobilization of cellulose extracted from Robinia Pseudoacacia seed fibers onto chitosan: Chemical characterization and study of methylene blue removal

The design of economical adsorbents to remove pollutants from contaminated water is attracting more attention. In this study, cellulose was successfully extracted from Robinia Pseudoacacia seed fibers and immobilized onto chitosan beads. The prepared spherical beads were then used for the biosorption of methylene blue dye from aqueous media. Samples were investigated using several analytical methods, namely FT-IR, XRD, EDX, SEM, and TGA analyses. The adsorption experiments showed that combining cellulose with chitosan improved the removal of methylene blue. The maximum uptake amount of methylene blue using cellulose–chitosan composite beads was 55 mg/g. However, it was about 35 mg/g at 20 °C for chitosan beads. The kinetic data complied strongly with the pseudo-second order equation, suggesting that the biosorption phenomenon has predominantly a chemical nature. Overall, the current study has shown a promising technique to design new adsorbents from abundant natural polymers for eliminating cationic dyes from water.     

A NOVEL APPROACH TO SYNTHESIZE CHITOSAN BEADS CROSSLINKED BY EPICHLOROHYDRIN

The present investigation describes a novel method for preparing spherical chitosan particles based on crosslinking with epichlorohydrin.Certain amount of pre-crosslinking agent was added to form chitosan gels by traditional inverse phase suspension polymerization.Then the gels were crosslinked by epichlorohydrin at basic condition to obtain chitosan beads.The effects of reaction conditions,such as crosslinking time,the amount of crosslinking agent and the NaOH concentration,on the physical properties of the chitosan beads were investigated.The beads were found to have more amino groups in the polymer chains than the beads crosslinked by glutaraldehyde.The capacity for copper ions in as high as 40mg/g,The beads have good mechanical strength and can be reused.     

A NOVEL APPROACH TO SYNTHESIZE CHITOSAN BEADS CROSSLINKED BY EPICHLOROHYDRIN

1. INTRODUCTION Chitosan is the deacetylated chitin which is one of the most abundant natural polymers produced from crab, lobster and shrimp shells or fungal fermentation processes [1]. It is a family of deacetylated β1→4 D-glucosamine polymers. Chitosan has properties including bioactivity, biocompatibility and biodegradability, so it is potentially more useful than cellulose for developing advanced of attention not only as an unutilized biomass resource but also as a novel type of sp…     

Chemical modification of methyl cellulose with HMDI to modulate the thickening properties in castor oil

This work deals with the selective incorporation of reactive isocyanate groups into methyl cellulose in order to be used as reactive thickening agent in castor oil. Resulting gel-like dispersions may have potential applications as green lubricating greases formulated from renewable resources. Two different isocyanate-functionalized methyl cellulose-based polymers were obtained by reaction of methyl cellulose with 1,6-hexamethylene diisocyanate. The functionalization degree, from fully functionalized to a certain number of free hydroxyl groups (58:36:6 ratio between –OMe, –NCO and free –OH groups), was controlled by modifying the reagents molar ratio. These polymers were characterized through nuclear magnetic resonance of protons (¹H-NMR), Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA). Thermal and rheological responses of oleogels prepared by dispersing these polymers in castor oil were studied by means of TGA analysis and small-amplitude oscillatory shear measurements. The evolution of linear viscoelasticity functions with frequency of the oleogel containing isocyanate-functionalized methyl cellulose with lower –NCO content is quite similar to that found for traditional lithium lubricating greases. In relation to long-term stability of these oleogels, the values of viscoelastic functions significantly increase during the first 7 days of ageing and then remain almost constant.     

Highly-porous uniformly-sized amidoxime-functionalized cellulose beads prepared by microfluidics with N-methylmorpholine N-oxide

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.

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Chemical interactions and yellowing in chitosan-treated cellulose

The chemical interactions between cellulose and chitosan were studied in chitosan-treated celluloses using diffuse reflectance spectroscopic techniques (UV-Vis and FTIR) and fluorescence spectroscopy. The materials were obtained by treating pure cotton cellulose with chitosan in dilute acetic acid solutions of different concentration, and some samples were exposed to different thermal treatments in air. Other related materials, including cellulose treated with benzyl amine and chitosan-treated with acetaldehyde, were also prepared and studied as models for chitosan-treated celluloses. The spectra of the treated celluloses showed new absorption and emission bands that revealed the existence of chemical interactions. These bands were assigned to conjugated imines produced in the reaction of the chitosan amino groups with cellulose carbonyl groups. The reaction is strongly amplified at temperatures above 100 °C, causing the intense yellowing of chitosan-treated celluloses.     

Self-assembly on natural cellulose: Towards high-efficient catalysts

Nanoarchitectures based on the layer-by-layer self-assembly technique hold great potential for the availability and applicability of bio-inspired functional materials. The introduction of various specific functional building blocks onto the nanofibers of natural cellulose substances (e.g., commercial filter paper, cotton, etc.) through the self-assembly approach provides a facile strategy for the fabrication of artificial nanomaterials. This review summarizes a series of cellulose-based catalytic materials fabricated by utilizing the natural cellulose substance as the structural scaffolds or templates through the LbL self-assembly process. The unique three-dimensional network porous structures and high surface areas of the cellulose substances were maintained by the resultant cellulose-derived catalysts, while the excellent mechanical strength of the cellulose-based membrane catalysts was inherited from the initial cellulose substrates. When employed for the photodegradation of organic dyes, the photocatalytic hydrogen production from water splitting, and the antibiosis, these cellulose-based catalysts exhibited high activities and excellent cycling stabilities.     

固定化木瓜蛋白酶的制备和性质研究

多孔硅球固定化木瓜蛋白酶具有热增活性 .本文在前文研究的基础上 ,用载体交联法制备了甲壳胺固定化木瓜蛋白酶和纤维素固定化木瓜蛋白酶 .考察了固定化pH值、戊二醛浓度和给酶量对固定化木瓜蛋白酶活力的影响 .研究了固定化木瓜蛋白酶的性质 ,特别是热稳定性和耐热性 ,并与溶液酶和多孔硅球固定化木瓜蛋白酶进行了比较 .所制得的甲壳胺固定化木瓜蛋白酶和纤维素固定化木瓜蛋白酶的最适反应温度均达到了 80℃ ;90℃温育 1h后固定化酶的活力保持在 95 %以上 ;70℃温育处理 5h和 6h后固定化酶的活力也仍能保持在 90 %以上 .固定化木瓜蛋白酶的热稳定性和耐热性得到了显著提高     

Surface carboxylation of porous regenerated cellulose beads by 4-acetamide-TEMPO/NaClO/NaClO2 system

A commercial regenerated bead cellulose was suspended in water at pH 4.8, and oxidized with NaClO₂ used as a primary oxidant and catalytic amounts of NaClO and 4-acetamide-2,2,6,6-tetramethylpiperidinyl-1-oxyl radical. Carboxylate groups were formed up to 1.87 mmol/g in the beads by the oxidation of C6 primary hydroxyls to carboxylates without significant weight losses or morphological changes. The spherical shapes, highly porous surface structures consisting of nano-sized fibrils, and the cellulose II crystal structure of the original beads were mostly maintained by the oxidation, indicating that the carboxylate groups formed are predominantly present on the fibril surfaces. Cation-exchange behavior of the TEMPO-oxidized cellulose beads was compared with carboxymethylated cellulose beads, showing that the former was characteristic and superior to the latter in terms of adsorption of metal ions and cationic polymers. Especially, the TEMPO-oxidized cellulose beads had high adsorption behavior of lead ion and high-molecular-weight cationic polymers.     

基于纤维素的先进功能材料（专题报道）

 收集整理了近几年间发表在国内外重要期刊上的约360篇文献,以纤维素功能材料的制备方法为线索,简要综述了该领域的最新进展,对纤维素基纤维材料、膜材料、光电材料、杂化材料、智能材料、生物医用材料等功能材料的制备过程、功能和应用前景做了概括性描述.     

Electrodes and hydrogel electrolytes based on cellulose: fabrication and characterization as EDLC components

In the present work, the cellulose-based materials were manufactured and used as components of electrochemical double layer capacitors (EDLCs). The preparation method of cellulose membranes as well as composite electrodes containing cellulose as a binder was presented. These materials were prepared using for the first time ionic liquid/dimethyl sulfoxide (IL/DMSO) mixture solvent. Obtained components displayed a uniform structure, thermal stability, and good electrochemical properties. The electrochemical performances of these materials were studied in 2-electrode EDLC cells by common electrochemical techniques as cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). The composite electrodes were investigated in three types of electrolytes: aqueous, organic, and ionic liquids. The cellulose membranes were, however, soaked in an aqueous electrolyte and tested as hydrogel polymer electrolytes. All investigated materials show high efficiency in terms of specific capacity. The studied cellulose-based capacitors exhibited specific capacitance values in the range of 20–22 F g^?1, depending on the type of applied electrolyte.     

Surface fluorination of paper in CF4-RF plasma environments

Plasma-based technologies are an exciting alternative for cellulose andpaper modification. Barrier coatings and surface functionalization of celluloseenhances properties and creates new possibilities for cellulose-based products.A parallel plate radio frequency (RF)-plasma reactor was used to modify papersubstrates under discharge parameters such as power, time and pressure. Carbontetrafluoride RF-plasma treatment of paper caused intense fluorination and itwas demonstrated that the fluorination reaction mechanisms can be controlled bythe external plasma parameters. Fluorine contents as high as 51.3% (contactangle=147°) were obtained for the treated cellulose. It was shown that eventreatment times as low as 30 s can generate relative surface fluorineatomic concentrations as high as 30%. High resolution ESCA and ATR-FTIRanalysisindicated covalently bound CF_x functional groups with CF₄treatment. It was found that under certain experimental conditionssuper-hydrophobic paper surfaces are created by combining the high surfacefluorine atomic concentrations with specific plasma-generated surfacetopographies.     

Cellulose-based materials as scaffolds for tissue engineering

Two types of cellulose-based materials, 6-carboxycellulose with 2.1 or 6.6 wt% of –COOH groups, were prepared and tested for potential use in tissue engineering. The materials were functionalized with arginine, i.e. an amino acid with a basic side chain, or with chitosan, in order to balance the relatively acid character of oxidized cellulose molecules, and were seeded with vascular smooth muscle cells (VSMC). The cell adhesion and growth were then evaluated directly on the materials, and also on the underlying polystyrene culture dishes. Of these two types of studied materials, 6-carboxycellulose with 2.1 wt% of –COOH groups was more appropriate for cell colonization. The cells on this material achieved an elongated shape, while they were spherical in shape on the other materials. The number of cells and the concentration (per mg of protein) of contractile proteins alpha-actin and SM1 and SM2 myosins, i.e. markers of the phenotypic maturation of VSMC, were also significantly higher on this material. Functionalization of the material with arginine and chitosan further improved the phenotypic maturation of VSMC. Chitosan also improved the adhesion and growth of these cells. In comparison with the control polystyrene dishes, the proliferation of cells on our cellulose-based materials was relatively low. This suggests that these materials can be used in applications where high proliferation activity of cells is not desirable, e.g. proliferation of VSMC on vascular prostheses. Alternatively, the cell proliferation might be enhanced by another more efficient modification, which would require further research.     

以离子液体为介质的纤维素加工与功能化

纤维素作为自然界中储量最大的天然高分子,被认为是未来世界能源与化工的主要原料.但由于分子链间存在丰富氢键网络以及高度结晶的聚集态结构特点,天然纤维素不熔化、难溶解,造成纤维素的加工极其困难,纤维素材料的传统生产工艺复杂且污染严重,极大限制了纤维素材料的广泛应用.近年来,人们发现一些特定结构的离子液体能够高效溶解纤维素,为纤维素的加工和功能化提供了新的多用途平台.本文从"溶解纤维素的离子液体、纤维素溶解机理与溶液性质、以离子液体制备再生纤维素材料和以离子液体为介质合成纤维素衍生物"4个方面详细介绍了本课题组在此领域的研究进展.     

Comparative Adsorption of Lead(II) on Flake and Bead‐Types of Chitosan

The adsorption of Pb(II) ions from aqueous solutions by chitosan flakes and beads was studied. The chitosan beads were prepared by casting an acidic chitosan solution into alkaline solution. Experiments were carried out as a function of pH, agitation period and initial concentration of Pb²⁺ ions. The uptake of Pb²⁺ ions from aqueous solution was determined from changes in concentration as measured by atomic absorption spectroscopy. The maximum uptake of Pb²⁺ ions on chitosan beads was greater than that on chitosan flakes. Adsorption isothermal data could be interpreted by the Langmuir equation. The experimental data of the adsorption equilibrium from Pb²⁺ ion solutions correlated well with the Langmuir isotherm equation. SEM analyses were also conducted for visual examination of the chitosan flakes and beads. Physical properties including surface area and average pore diameter were characterized by N₂ adsorption experiment.     

Preparation and chiral recognition ability of crosslinked beads of polysaccharide derivatives

The spherical beads consisting of cellulose 3,5-dimethylphenylcarbamate with partial hydroxyl groups were prepared to be used as chiral packing materials (CPMs) for HPLC. The beads were obtained without using macroporous silica gel, which is usually used as the support of the CPMs based on the polysaccharide derivatives. After the crosslinking in the bead with diisocyanates, such as 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dibenzyl diisocyanate (DBDI), tolylene-2,4-diisocyanate (TDI), and m-xylylene diisocyanate (XDI), the obtained beads were packed into an HPLC column. As the content of the hydroxyl groups of the cellulose derivatives decreased, the obtained CPM exhibited a higher chiral recognition ability. The beads possessed a higher loading capacity than the CPM prepared by coating the cellulose derivative on silica gel. The crosslinked beads could be used with the eluent containing chloroform. The amylose derivative beads were also prepared as a CPM for chiral HPLC.     

Preparation and Properties of Interpolymer Complexes Capable of Soil Structuring

Complexation between biopolymers, chitosan cationic polyelectrolyte and sodium carboxymethyl cellulose anionic polyelectrolyte, was studied. The composition of the interpolymer complex formed was determined by conductometry and Fourier IR spectroscopy. The interpolymer complex and the initial complex-forming polymers were used for the first time as soil-structuring agents in urban soils. Treatment of urban soil with the interpolymer complex led to aggregation of soil particles and improved the water permeability of the soil.

     

Biocompatible hydrogels based on chitosan,cellulose/starch,PVA and PEDOT:PSS with high flexibility and high mechanical strength

Fabricating mechanically strong hydrogels that can withstand the conditions in internal tissues is a challenging task. We have designed hydrogels based on multicomponent systems by combining chitosan, starch/cellulose, PVA, and PEDOT:PSS via one-pot synthesis. The starch-based hydrogels were homogeneous, while the cellulose-based hydrogels showed the presence of cellulose micro- and nanofibers. The cellulose-based hydrogels demonstrated a swelling ratio between 121 and 156%, while the starch-based hydrogels showed higher values, from 234 to 280%. Tensile tests indicated that the presence of starch in the hydrogels provided high flexibility (strain at break?>?300%), while combination with cellulose led to the formation of stiffer hydrogels (elastic moduli 3.9–6.6 MPa). The ultimate tensile strength for both types of hydrogels was similar (2.8–3.9 MPa). The adhesion and growth of human osteoblast-like SAOS-2 cells was higher on hydrogels with cellulose than on hydrogels with starch, and was higher on hydrogels with PEDOT:PSS than on hydrogels without this polymer. The metabolic activity of cells cultivated for 3 days in the hydrogel infusions indicated that no acutely toxic compounds were released. This is promising for further possible applications of these hydrogels in tissue engineering or in wound dressings.

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Polyelectrolyte capsules made of two biocompatible natural polymers

In this study the influence of the experimental conditions on the obtention of polyelectrolyte multilayer capsules was investigated. Two ways of the simple coacervation method was used to obtain spherical capsules involving chitosan and hyaluronan, chitosan being inside the particle covered by a hyaluronan layer to increase the biocompatibility. The ¹H-NMR spectroscopy confirmed a polyelectrolyte complex formation and the optical microscopy shows that the complexed capsules have good sphericity with average diameters ranging from 590 at 1550 μm in the experimental conditions adopted. One can observe that in the acid medium the complexed capsules are much stable than the chitosan beads. The structures described provide a starting point for the design and fabrication of complexed capsules made of two biocompatible natural polymers with potential applicability in medical or pharmaceutical applications. Few diffusion experiments demonstrated that the complexed layer controls the diffusion of dextran included in the chitosan inner domain.