In the 21st century, science and technology have moved toward renewable raw materials and more environmentally friendly and sustainable resources and processes.[1] The Technology Road Map sponsored by the U.S. Department of Energy (DOE) has targeted to achieve 10 % of basic chemical building blocks arising from plant-derived renewable sources by 2020. [2] Cellulose is the most abundant renewable organic material and can be converted into cellulose derivatives (ethers and esters) and regenerated materials (fibers, films, food casings, membranes, and sponges, among others).[3] Moreover, numerous new functional materials of cellulose are being developed over a broad range of applications. [1a,4] It is noted that the traditional viscose route for producing regenerated cellulose fibers, films, and nonwoven fabrics still dominates the current processing route.[1a] The viscose route is technologically complex and requires additional facilities to treat the gaseous and aqueous waste emissions (end-of-pipe technology), which makes it a growing urgency to develop a new pathway to avoid the complicated current routes and hazardous byproducts. An more environmentally friendly process of cellulose-fiber spinning using a direct solvent system, N-methylmorpholine-N-oxide (NMMO), has been developed, leading to a new class of man-made cellulose fibers with the generic name of Lyocell.[5]Lyocell fibers show better performance qualities, but the Lyocell process suffers from 1) uncontrolled thermal stability of the system NMMO-cellulose-H 2 O (a runaway reaction),2) high evaporation costs (energy costs), and 3) high tendency of fibrillation of the Lyocell fiber. [3,5] Faced with the serious pollution produced by the viscose method in China, India, and other countries, we hope to realize a dream of producing regenerated cellulose materials using the new route by using low-cost chemical reagents and a simple wet-spinning process that yields essentially nontoxic byproducts. In previous work, we developed a novel solvent system for cellulose, that is, an NaOH/urea aqueous solution precooled to -12°C, in which the dissolution of cellulose could be achieved rapidly at ambient temperatures (below 20°C).[6] Interestingly, cellulose with a relatively high molecular weight could not be dissolved in the solvent without being precooled to -12°C or without urea being added. The addition of urea and the low temperature play an important role in the improvement of the cellulose dissolution, because low temperature creates a large inclusion complex associated with cellulose, NaOH, urea, and H 2 O clusters, which bring cellulose into aqueous solution, even at relatively high cellulose concentrations. Moreover, the cellulose dope could remain in a liquid state for a long time period at about 0 to 5°C. [7] It has motivated us to develop a more economical and environmentally friendly cellulose-fiber-fabrication process on an industrial scale in order to demonstrate the utility of this solvent system. Here, we present a first attempt to prepare the wet...

Quaternized celluloses (QCs) were homogeneously synthesized by reacting cellulose with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) in NaOH/urea aqueous solutions. The structure and solution properties of the QCs were characterized by using elemental analysis, FTIR, (13)C NMR, SEC-LLS, viscometer, and zeta-potential measurement. The results revealed that water-soluble QCs, with a degree of substitution (DS) value of 0.20-0.63, could be obtained by adjusting the molar ratio of CHPTAC to anhydroglucose unit (AGU) of cellulose and the reaction time. The QC solutions in water displayed a typical polyelectrolyte behavior, and the intrinsic viscosity ([eta]) value determined from the Fuoss-Strauss method increased with increasing DS value. Moreover, two QC samples (DS = 0.46 and 0.63) were selected and studied as gene carriers. The results of gel retardation assay suggested that QCs could condense DNA efficiently. QCs displayed relatively lower cytotoxicity as compared with PEI, and QC/DNA complexes exhibited effective transfection compared to the naked DNA in 293T cells. The quaternized cellulose derivatives prepared in NaOH/urea aqueous solutions could be considered as promising nonviral gene carriers.

Responsive behavior has become a key requirement for advanced artificial materials and devices. 1 Especially, environmentally sensitive hydrogels which contain functional groups have received increasing attention in many applied scientific fields including medicine, pharmaceutics, agriculture, and material science. [2][3][4][5][6][7][8][9] The smart behavior of hydrogels is generally based on noncovalent dynamic bonding, e.g., hydrogen bonding, hydrophobic, π-π stacking, and electrostatic interactions. [10][11][12][13][14][15] Depending on the backbone structure and composition, such hydrogels can be designed to respond to external stimuli such as temperature, pH, salt, light, and electric field. [16][17][18][19][20] The majority of the work in environmentally sensitive hydrogels has been focused on synthesized polymers. There has also been significant attention on natural polymers. 21 It is noted that the hydrogels prepared from natural polymers, such as alginate, 22 chitosan, 23,24 gelatin, 25 starch, 26 cellulose, 27 and collagen, 28 have many inherent advantages such as biodegradability, biocompatibility, and their natural abundance. As a result of their good biocompatibility, these hydrogels can be used to deliver a number of therapeutics, such as enzymes, antibacterial, antibodies, vaccines, contraceptives, and hormones. 29 Cellulose, the most abundant resource in nature, has been chosen as a good candidate for fabricating hydrogels owing to its hydrophilicity, biodegradability, and safety. Moreover, the utilization of cellulose to prepare materials is in accord with the theme of "Chemistry for a Sustainable World" in 239th ACS National Meeting. Recently, we have developed a novel solvent

Cellulose based ZnO nanocomposite (RCZ) films were prepared from cellulose carbamate-NaOH/ZnO solutions through one-step coagulation in Na2SO4 aqueous solutions. The structure and properties of RCZ films were characterized using XRD, FTIR, XPS, SEM, TEM, TG, tensile testing, and antibacterial activity tests. The content of ZnO in RCZ films was obtained in the range of 2.7-15.1 wt %. ZnO nanoparticles with a hexagonal wurtzite structure agglomerated into large particles, which firmly embedded in the cellulose matrix. RCZ films displayed good mechanical properties and high thermal stability. Moreover, the films exhibited excellent UV-blocking properties and antibacterial activities against Staphylococcus aureus and Escherichia coli. A dramatic reduction in viable bacteria was observed within 3 h of exposure, while all of the bacteria were killed within 6 h. This work provided a novel and simple pathway for the preparation of regenerated cellulose films with ZnO nanoparticles for application as functional biomaterials.

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ABSTRACT:NaOH/urea aqueous solution as solvent of cellulose including cotton linter, bagasse, alkali-soluble cellulose and Bemliese'" was studied by solubility analysis, viscometry and light scattering. The addition of 2-4 wt% urea significantly improved the solubility of cellulose in 6-8 wt% Na OH aqueous solutions, and moderate urea plays a role in improving solubility and avoiding the formation of cellulose gel. Celluloses I with viscosity-average molecular weight (M ry) of 6. 7 X 10 4 were completely dissolved in 6 wt% NaOH/4 wt% urea aqueous solution. Cellulose dissolved in 6 wt% N aOH/4 wt% urea aqueous solution degraded slowly with storage time, and M ry of cellulose in the solution decreased 20% after storage for 100 days. The stability of cellulose solution was higher than cellulose cuoxam. A regenerated cellulose membrane having the tensile strength of 88. 7 MPa and breaking elongation of 11 % was successfully prepared by coagulating 4 wt% Bemliese" solution in 6 wt% NaOH/4 wt% urea with 5 wt% CaCl 2 then 1.3 wt% HCl aqueous solution as coagulate at 20°C.KEY WORDS NaOH I Urea Aqueous Solution/ Solubility/ Viscosity/ Stability of Cellulose/ Regenerated Cellulose Membrane I Polymers from renewable resources attract much attention due to biodegradability and potential as substitute for petrochemicals in some fields. Plant cellulose is the richest natural polymer on the earth. Making use of cellulose to produce various products cannot only protect the environment from pollution, but save limited petroleum resources. 1 However, the molecular structure of cellulose, (3-( 1---+4)-D-glucan, allows chain-packing by strong inter-and intramolecular hydrogen-bonding, which interferes with efforts to process or modify the material. 2 Therefore, cellulose still has not reached its potential in many areas for all its availability. The most general solvents for dissolving cellulose are unsuitable.It is worth noting that in the viscose industry, pollution control places ever increasing restraint on the process. 3 The development of non-polluting process based on organic and inorganic solvents of cellulose is of great scientific or practical interest, and much attention should be given to such solvents as ammonia/ammonium thiocyanate,4·5 calcium-and sodium thiocyanate, 6 · 7 zinc chloride,s-io lithium chloride/dimethylacetamide, 2 · •12 Nmethylmorpholine-N-oxide13-15 and aqueous solution of sodium hydroxide. •17 N-methylmorpholine-N-oxide has been recognized as a direct cellulose solvent, but commercial facility producing cellosic fibers via this solvent has developed very slowly due to high cost and high spinning temperature. 1 s 7-9 wt% NaOH aqueous solution is one of the cheapest cellulose solvents, in which cellulose can be dissolved near 4 °C, since intermolecular hydrogen bonds are destroyed. 16 · 19 However, only from cellulose of relatively low molecular weight is impossible to obtain fibers, and cellulose with polymerization of over 250 is unstable_ is Kamide, Okajima, and coworkers 16 • 17 · 20 -22 report that...

Regenerated cellulose (RC) films having various viscosity-average molecular weights (M η ) ranging from 2.2 × 10 4 to 8.2 × 10 4 g/mol were prepared from cotton linters in 6 wt % NaOH/4 wt % urea aqueous solution by coagulation with 2 M acetic acid and 2% H 2 SO 4 aqueous solution. The dissolution of cellulose and the structure, transparency, and mechanical properties of the RC films were investigated by 13 C NMR, ultraviolet, and infrared spectroscopies; scanning electron microscopy; X-ray diffraction; and a strength test. The RC films exhibited the cellulose II crystalline form and a homogeneous structure with 85% light transmittance at 800 nm. 13 C NMR spectroscopy indicated that the presence of urea in NaOH aqueous solution significantly enhanced the intermolecular hydrogen bonding between cellulose and the solvent, resulting in a higher solubility of cellulose and the complete transition of its crystalline form from I to II. The tensile strength (σ b ) of the RC films in the dry state increased with increasing M η up to 6.0 × 10 4 g/mol and then hardly changed. The values of σ b and the breaking elongation ( b ) of the RC film having M η ) 6.0 × 10 4 g/mol by coagulation with 2% H 2 SO 4 were found to be 106 MPa and 8.0%, respectively, in the dry state and 17.0 MPa and 10.7%, respectively, in the wet state, and the strength was much higher than that of commercially available cellophane. Therefore, a novel and nonpolluting process for the manufacture of cellulose film and fiber from cotton linters in 6 wt % NaOH/4 wt % urea aqueous solution is provided in this work.

Regenerated cellulose (RC) films coated with copper (Cu) nanoparticles were prepared from cellulose-cuprammonium solution through coagulation in aq. NaOH and subsequent reduction in aq. NaBH4. Structure and morphology of the nanocomposite films were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results established the migration of Cu(2+) from the inner to the surface of the RC films during the coagulation of cellulose-cuprammonium solution and the reduction from Cu(2+) to Cu(0). Cu nanoparticles were found to be firmly embedded on the surface of the RC films. The RC films coated with Cu nanoparticles showed efficient antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The dramatic reduction of viable bacteria could be observed within 0.5 h of exposure, and all of the bacteria were killed within 1 h.