Aixue Dong

Hydrophobic surface functionalization of lignocellulosic jute fabrics by enzymatic grafting of octadecylamine

Enzymatic grafting of synthetic molecules onto lignins provides a mild and eco-friendly alternative for the functionalization of lignocellulosic materials. In this study, laccase-mediated grafting of octadecylamine (OA) onto lignin-rich jute fabrics was investigated for enhancing the surface hydrophobicity. First, the lignins in jute fabrics were isolated and analyzed in the macromolecular level by MALDI-TOF MS, (1)H NMR, (13)C NMR, and HSQC-NMR. Then, the surface of jute fabrics was characterized by FT-IR, XPS, and SEM. Subsequently, the nitrogen content of jute fabrics was determined by the micro-Kjeldahl method, and the grafting percentage (Gp) and grafting efficiency (GE) of the enzymatic reaction were calculated. Finally, the surface hydrophobicity of the jute fabrics was estimated by contact angle and wetting time measurements. The results indicate that the OA monomers were successfully grafted onto the lignin moieties on the jute fiber surface by laccase with Gp and GE values of 0.712% and 10.571%, respectively. Moreover, the modified jute fabrics via OA-grafting showed an increased wetting time of 18.5 min and a contact angle of 116.72°, indicating that the surface hydrophobicity of the jute fabrics increased after the enzymatic grafting modification with hydrophobic OA molecules.

Conductive cotton prepared by polyaniline in situ polymerization using laccase

The high-redox-potential catalyst laccase, isolated from Aspergillus, was first used as a biocatalyst in the oxidative polymerization of water-soluble conductive polyaniline, and then conductive cotton was prepared by in situ polymerization under the same conditions. The polymerization of aniline was performed in a water dispersion of sodium dodecylbenzenesulfonate (SDBS) micellar solution with atmospheric oxygen serving as the oxidizing agent. This method is ecologically clean and permits a greater degree of control over the kinetics of the reaction. The conditions for polyaniline synthesis were optimized. Characterizations of the conducting polyaniline and cotton were carried out using Fourier transform infrared spectroscopy, UV–vis spectroscopy, cyclic voltammetry, the fabric induction electrostatic tester, and the far-field EMC shielding effectiveness test fixture.

Jute/polypropylene composites: Effect of enzymatic modification on thermo-mechanical and dynamic mechanical properties

In this study, a high-performance composite was prepared from jute fabrics and polypropylene (PP). In order to improve the compatibility of the polar fibers and the non-polar matrix, alkyl gallates with different hydrophobic groups were enzymatically grafted onto jute fabric by laccase to increase the surface hydrophobicity of the fiber. The grafting products were characterized by FTIR. The results of contact angle and wetting time showed that the hydrophobicity of the jute fabrics was improved after the surface modification. The effect of the enzymatic graft modification on the properties of the jute/PP composites was evaluated. Results showed that after the modification, tensile and dynamic mechanical properties of composites improved, and water absorption and thickness swelling clearly decreased. However, tensile properties drastically decreased after a long period of water immersion. The thermal behavior of the composites was evaluated by TGA/DTG. The fiber-matrix morphology in the modified jute/PP composites was confirmed by SEM analysis of the tensile fractured specimens.

Laccase-mediated in situ oxidation of dopa for bio-inspired coloration of silk fabric

Bio-inspired or bionic coloration of fiber assemblies based on chemical oxidation of phenolics has gained more and more attention in recent years. To overcome the challenges of protecting the ecology and environment in textile processes, a novel approach for the coloration of silk fabrics via laccase-mediated in situ oxidation of dopa (dihydroxy phenylalanine) has been investigated in this work. In view of the fact that laccase is able to catalyze the oxidation of benzenediol followed by polymerization to produce strongly colored phenolic polymers, two biological coloration processes of silk fabrics based on in situ oxidation of dopa using laccase were investigated: (i) the adsorption of silk fabrics with dopa, followed by further catalysis of laccase and (ii) the simultaneous laccase-mediated polymerization and coloration of silk fabrics. Dosages of laccase and incubation time were evaluated in order to increase the color depth and fastness of the silk fabrics. The increase in laccase dosage and reaction time allowed improvement in the depth of the final color. The properties of colored silk fabrics were evaluated in terms of UV-protection and color fastness. Finally, the binding of the polymers of dopa with silk fibers was verified by Fourier transform infrared spectroscopy (FT-IR). The silk fabrics treated with laccase/dopa by a one-step process obtained K/S values of 16.935, light fastness of 4–5 level, and UPF of 100+. SEM and AFM observations showed that the surface of silk samples treated with laccase/dopa had numerous small flakes, which can be regarded as the melanin particles of dopa molecules, attached by the grafting reaction. The FT-IR analysis showed that the functional groups on the surfaces of laccase/dopa-treated silk fabrics were changed with the introduction of carbonyl groups. The results of XPS showed that the elemental composition of the surface of laccase/dopa-treated silk fabrics was similar to oral melanin. This dyeing technique could also be extended to the treatments of other types of fibers in textile dyeing and finishing processes.

Changes on Content, Structure and Surface Distribution of Lignin in Jute Fibers After Laccase Treatment

ABSTRACT Effect of laccase treatment on the content, structure, and surface distribution of lignin in jute fibers were fundamentally investigated. Four percent lignin was removed from jute fibers via the laccase treatment. The residual lignin in the laccase-treated jute fibers showed increased molecular weights, which indicated polymerization between lignins on jute fibers. Meanwhile, the phenolic hydroxyl content in lignin decreased during the laccase oxidation accompanied by demethylation of methoxyl groups and generation of carbonyl groups. Due to the degradation and subsequent polymerization of lignin by laccase, the bulgy lignins on jute fiber surfaces were redistributed, which made the surface neat and glossy.

Enzymatic modification of jute fabrics for enhancing the reinforcement in jute/PP composites

In this work, laccase was employed to improve the properties of lignocellulosic jute fabrics and then the modified jute was used as the fiber reinforcement of polypropylene (PP) matrix composites to improve its reinforcing effect on the polymer resins and obtain composite materials with better performance. The decrease in the –C–O–H component and the increase in the –C–O–C component on the surface of laccase-treated jute fabrics suggested that phenolic hydroxyl groups of lignins on the jute fiber surface were oxidized by laccase and the produced phenoxyl radicals were coupled to form ether structures. The laccase-treated jute fiber surface became smooth with lignins attached tightly. Moreover, the surface hydrophobicity and tensile properties of the jute fabrics were increased via the laccase-mediated reactions of lignins. PP composites reinforced by the laccase-treated jute fabrics showed higher breaking strength, storage modulus, and melting temperature than the control. The fracture surface of the laccase-treated jute fabric/PP composites was neat and jute fibers on the section surface were surrounded by PP resins closely, which indicated better interfacial adhesion between the modified jute reinforcement and PP matrix.

Hydrophobic functionalization of jute fabrics by enzymatic-assisted grafting of vinyl copolymers

We report an eco-friendly approach to improve the hydrophobicity of jute fabrics via horseradish peroxidase (HRP)-catalyzed covalent grafting of butyl acrylate (BA) and 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA). Hydrophobic vinyl monomers were grafted onto the exposed lignin molecules of the jute surface by free-radical polymerization in the presence of a HRP/H2O2/acetylacetone (ACAC) system. Coupling onto the lignin–jute surface was demonstrated by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), solid-state nuclear magnetic resonance (solid-state 19F NMR), elemental analyses, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) and scanning electron microscopy (SEM). The hydrophobicity and oleophobicity of modified jute fabrics was estimated in terms of contact angle and wetting time. The results indicated that it was essential to attain vinyl monomers grafting polymerization onto jute surfaces in a HRP/H2O2/ACAC system. Moreover, the grafting of vinyl monomers led to hydrophobicity increases of 53.86% and 61.03% in the contact angle of grafted jute fabrics with BA and HFBMA when compared with unmodified jute fabrics, respectively. Both vinyl monomers demonstrated high propensity to be polymerized by HRP in the presence of H2O2, and acquired the ability to act as high-performance composites with hydrophobic resins.

Characterization and performance of ramie fabrics treated with modified cellulase

In this study, a modification procedure for ramie fabrics was developed using modified cellulases. Cellulase was modified by covalent coupling to Eudragit S-100, which resulted in a larger molecule, to trigger its activity toward the cellulosic fiber surface. The modified fabrics were characterized by using atomic force microscope, thermogravimetric analysis, and Kawabata Evaluation System for Fabric techniques in order to determine their morphology, thermal stability, and handle. In addition, the moisture evaporation, wicking property, and air permeability of the modified ramie fabrics were investigated. Furthermore, the weight loss and copper number were determined to identify the damages in the modified ramie fibers. The results show that the modified cellulase can prevent excessive damage to ramie fabrics with the desired performance because the hydrolytic attack of the modified cellulase is restricted to the surface of the ramie fibers.

Mechanism and Analysis of Laccase-mediated Coloration of Silk Fabrics

Laccase provides a mild and eco-friendly alternative for the dyeing of fabrics. In this study, laccase-mediated catalytic oxidation was employed in coloration of silk fabrics, and the color was then assessed. The surfaces of silk fabrics were characterized by scanning electron microscope (SEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). Their thermal and crystallization properties were also investigated by differential scanning calorimetry (DSC), thermogravimetry (TG), and Xray diffraction (XRD). The textile softness was evaluated by the bending rigidity (B). In addition, high performance liquid chromatography (HPLC) and ultraviolet-visible (UV-VIS) spectroscopy were employed to analyze hydrolysate of silk fabrics obtained from hydrolysis with hydrochloric acid solution. The results demonstrated that a stable reddish-yellow layer was formed on the surface of silk fabrics by the laccase-mediated coupling of phenol hydroxyl side chains in the silk polypeptide. Moreover, the SEM and AFM observations showed that the surface of colored silk fiber was slick. ATR-FTIR and XPS results demonstrated differences in the C, N, O contents and the functional groups of the uncolored and colored silk fabrics. The DSC, TG, and XRD indicated that the thermal properties of silk fabrics were not affected by laccase and the coupling reaction mainly occurred in the amorphous region. The DMF extraction test further illustrated that covalent bonds were formed between tyrosine residues constituent of silk peptides. Finally, HPLC and UV-VIS results showed that new substances were formed as a result of conjugation between benzene rings.

Enzymatic coating of jute fabrics for enhancing anti-ultraviolent properties via in-situ polymerization of polyhydric phenols:

To enhance the anti-ultraviolent properties of technical jute fabrics, the enzymatic surface coating with the in-situ produced phenolic polymers of polyhydric phenols was investigated in this study. Firstly, the laccase-mediated polymerization of the five polyhydric phenols (catechol, resorcinol, hydroquinone, pyrogallol and phloroglucinol) was analyzed by FT-IR. Catechol and pyrogallol were polymerized together by laccase with ether bonds linked. On the contrary, the units of resorcinol, hydroquinone and phloroglucinol in their enzymatically formed polymers concatenated to each other by C-C bonds. Then, the coated jute fabrics were characterized in terms of X-ray photoelectron spectroscopy and scanning electron microscopy. The increasing of the C/O ratio on the jute fabric surface after the coating treatments supported the achievement of the enzymatic coating on jute fabrics via the in-situ polymerization of phenolic compounds and the grafting reaction of polyphenols with lignins on the surface. The sequence of the coating extent by using various polyhydric phenols was proved to be catechol, pyrogallol, resorcinol, phloroglucinol and hydroquinone in order from rich to poor according to the O-C-O component of cellulose in the C1s spectra of jute fabrics and the scanning electron microscopy photographs of jute surfaces. Lastly, the ultraviolent protection factor and the ultraviolent resistance of the coated jute fabrics were measured. The ultraviolent protective performance of jute fabrics after the coating treatments depended both on the coating amount and the chemical structure of the coated polymers. Among the tested polyhydric phenols, the polymerization of catechol obtained the best coating for ultraviolent protection. Different polyhydric phenols employed for the enzymatic coating showed different trends in ultraviolent protection factor of jute fabrics with the increasing of incubation time. The jute fabrics coated with in-situ-generated polycatechols or polyresorcinols had excellent ultraviolent resistances.