5 research outputs found

    Honeycomb Films of Cellulose Azide: Molecular Structure and Formation of Porous Films

    No full text
    Development of value-added micropatterned porous materials from naturally abundant polymers, such as cellulose, are of growing interest. In this paper, regioselectively modified amphiphilic cellulose azide, 3-<i>O</i>-azidopropoxypoly­(ethylene glycol)-2,6-di-<i>O</i>-thexyldimethylsilyl cellulose, with different degrees of substitution (DS) and degrees of polymerization (DP) of the poly­(ethylene glycol) (PEG) side chain, was synthesized and employed in the formation of honeycomb-patterned films. With the variation of the DP and/or DS, the amphiphilicity of the polymer and the pore size of the formed films changed accordingly. It was found that amphiphilicity of the cellulose azide played a significant role in the formation of honeycomb films. Balanced amphiphilicity was of particular importance in the formation of uniform honeycomb films. Via the Cu<sup>I</sup>-catalyzed alkyne–azide [2 + 3] cycloaddition reaction, fluorescent avidin and quantum dots were attached to the films. By means of confocal microscopy, it was confirmed that the functional azido group was preferentially allocated inside the pores. This provides a platform for the development of advanced honeycomb materials with site-specific functionalities, such as biosensors

    Preparation and Characterization of Kraft Lignin-Based Moisture-Responsive Films with Reversible Shape-Change Capability

    No full text
    Preparation of moisture-responsive Kraft lignin-based materials by electrospinning blends of Kraft lignin fractions with different physical properties is presented. The differences in thermal mobility between lignin fractions are shown to influence the degree of interfiber fusion occurring during oxidative thermostabilization of electrospun nonwoven fabrics, resulting in different material morphologies including submicrometer fibers, bonded nonwovens, porous films, and smooth films. The relative amount of different lignin fractions and degree of fiber flow and fiber fusion is shown to influence the tendency for the electrospun materials to be transformed into moisture-responsive materials capable of reversible changes in shape. Material characterization by scanning electron microscopy and atomic force microscopy as well characterization of the chemical and physical properties of Kraft lignin fractions by dynamic rheology, <sup>1</sup>H and <sup>13</sup>C NMR, and gel permeation chromatography combined with multiangle laser light scattering are presented. A proposed mechanism underlying moisture-responsiveness, shape change, and shape recovery is discussed based on the differences in chemical structure and physical properties of Kraft lignin fractions

    Design of Functionalized Cellulosic Honeycomb Films: Site-Specific Biomolecule Modification via “Click Chemistry”

    No full text
    Value-added materials from naturally abundant polymers such as cellulose are of significant importance. In particular, cellulosic open-framework structures with controlled chemical functionality of the internal surface have great potential in many biosensor applications. Although various cellulose derivatives can form porous honeycomb structured materials, solubility issues and problems with film formation exist. To address this, we have generated robust cellulosic open-framework structures that can be post-functionalized through site-specific modification. Regioselectively modified amphiphilic cellulose azides, 3-<i>O</i>-azidopropoxypoly­(ethylene glycol)-2,6-di-<i>O</i>-thexyldimethylsilyl cellulosics, were synthesized, and honeycomb-patterned films were readily produced by the simple breath figures method. Changing the degree of polymerization (DP) of the pendent ethylene glycol (EG<sub>DP</sub>) groups from 22 to 4 increased the corresponding honeycomb film pore diameters from ∼1.2 to ∼2.6 μm, enabling the potential tuning of pore size. Moreover, these novel azido-functionalized honeycomb films were easily functionalized using Cu­(I)-catalyzed alkyne–azide [2 + 3] cycloaddition reaction; biotin was “clicked” onto the azide functionalized cellulosic honeycomb films without any effect to the film structure. These results indicate this system may serve as a platform for the design and development of biosensors

    Characterization of Fractions Obtained from Two Industrial Softwood Kraft Lignins

    No full text
    With increasing interest in using lignin as an alternative material to petroleum-based chemicals (e.g., in the manufacture of carbon fibers or adhesives), it is becoming important to understand what properties of lignin are required to impart key features in the final product. Commercial lignins are complex, heterogeneous, macromolecular mixtures. To obtain maximum value, lignins will require classification and possibly fractionation or modification to improve properties and enable their utilization in high-value applications. To this end, the physicochemical properties of fractions derived from two industrial softwood Kraft lignins (New Bern Mill, Weyerhaeuser, U.S.A., and Backhammar Mill in Kristinehamn, Sweden) have been determined and compared to previously published data on commercially available Indulin AT lignin from MeadWestvaco., The fractions were obtained by successive extraction with organic solvents and analyzed using a range of techniques (e.g., DSC, <sup>13</sup>C NMR, <sup>31</sup>P NMR). The results showed that these industrial softwood Kraft lignins varied significantly in both the amounts of the various fractions and in the properties of the analogous fractions. These differences emphasize the issues industry faces in the utilization of industrial lignins for high-value applications where minor inconsistencies between lignin sources could pose major technical challenges

    Improved Manganese-Oxidizing Activity of DypB, a Peroxidase from a Lignolytic Bacterium

    No full text
    DypB, a dye-decolorizing peroxidase from the lignolytic soil bacterium <i>Rhodococcus jostii</i> RHA1, catalyzes the peroxide-dependent oxidation of divalent manganese (Mn<sup>2+</sup>), albeit less efficiently than fungal manganese peroxidases. Substitution of Asn246, a distal heme residue, with alanine increased the enzyme’s apparent <i>k</i><sub>cat</sub> and <i>k</i><sub>cat</sub>/<i>K</i><sub>m</sub> values for Mn<sup>2+</sup> by 80- and 15-fold, respectively. A 2.2 Å resolution X-ray crystal structure of the N246A variant revealed the Mn<sup>2+</sup> to be bound within a pocket of acidic residues at the heme edge, reminiscent of the binding site in fungal manganese peroxidase and very different from that of another bacterial Mn<sup>2+</sup>-oxidizing peroxidase. The first coordination sphere was entirely composed of solvent, consistent with the variant’s high <i>K</i><sub>m</sub> for Mn<sup>2+</sup> (17 ± 2 mM). N246A catalyzed the manganese-dependent transformation of hard wood kraft lignin and its solvent-extracted fractions. Two of the major degradation products were identified as 2,6-dimethoxybenzoquinone and 4-hydroxy-3,5-dimethoxybenzaldehyde, respectively. These results highlight the potential of bacterial enzymes as biocatalysts to transform lignin
    corecore