| Along with increasing public awareness on environmental protection,the development of environment-friendly dyeing and finishing processes has attracted much attention of researchers at home and abroad.Biological dyeing using oxidoreductase as a catalyst is regarded as a“green”approach which can be executed under milder conditions without using toxic solvents.In this study,wool and cotton fabrics were seclected as research objects.Laccase can catalyze the polymerization of aromatic compounds such as catechol,hydroquinone and caffeic acid to produce colored multipolymers,which realized the combination of polymerization and coloration and established laccase catalyzed biological dyeing process;exogenous templates(polyethylene glycol,chitosan oligosaccharides and chitosan)were introduced to improve the color depth of the enzymatically polymerized dyed fabrics;Polymers produced by laccase catalysis of some aromatic compounds could endow fabrics with certain electrical conductivity,wetting properties and antibacterial properties.The main research contents and conclusions are listed:Firstly,catechol and hydroquinone were polymerized using laccases,respectively.Possible structures and bonding modes of polymer complex were analyzed by UV-Vis,FTIR,and MALDI-TOF MS measurements;wool fabrics were dyed with laccase in the presence of precursor(catechol)using one-step method(ie,precursor,laccase and fabrics are added to the reaction system,enzymatic polymerization and dyeing of wool fabric were simultaneously undertaken)and two-step method(ie,polymerization of precursor under laccase catalysis first,followed by dyeing of fabrics;precursor pre-adsorbed on the fiber surface,followed by laccase-catalyzed polymerization).The effects of processing conditions and treatment paths on wool dyeing were discussed in terms of the color depth,color fastness and surface morphology of wool samples.Four monomers(o-aminophenol,p-aminophenol,p-phenylenediamine and 2,5-diaminobenzenesulfonic acid)were selected as precursors to produce colored polymers for the dyeing of fabrics and explore the relationship between the structure and color of the enzymatic polymerization products via laccase catalysis,which structures were similar to catechol and hydroquinone.The results showed that phenoxy bonding(ph-O)and phenyl-phenyl bonding(ph-ph)are realized by dehydrogenation among monomers;it was confirmed that the coloration obtained by the one-step method showed the best effect.The optimum conditions:20 mM of catechol,0.06 U/mL of laccase,liquor-to-fabric ratio of 200:1,pH 5.0,50°C,the agitation was set at 50 rpm;enzymatic polymerization products of aromatic compounds are conjugated with benzene rings to form a chromophore,phenolic hydroxyl groups and amino groups as auxomchromes.The positions and numbers of auxomchromes on the benzene ring will make different colors,such as yellow brown,purple,reddish brown,etc.Secondly,the enzymatic polymerization of the aromatic compound-pyrrole and the dyeing of the wool fabrics were investigated.Polypyrrole dyed wool fabrics with conductive function was simultaneously obtained.The influence of different periods on the polymerization of pyrrole catalyzed by laccase was examined in terms of ultraviolet visible(UV-Vis)spectra.The structure of the polymerized product was characterized by ~1H NMR.The effects of process conditions on the dyeing properties and electrical conductivity of wool fabrics were investigated.Surface morphology of the dyed wool fibers was studied by scanning electron microscopy(SEM).The electrochemical activity and dyeing properties of the dyed wool fabrics were evaluated by cyclic voltammetry(CV)curve,K/S value and color fastness.The results showed that the polymerized pyrrole connected by carbon-carbon bond of amino-ortho-position carbon under laccase catalysis.Three different colors could be obtained through adjusting the dyeing conditions as well,namely light green,dark green and blackish green.Polypyrrole was successfully coated on the dyed wool fabric,and better soap fastness and rubbing fastness(grade 4-5)of dyed wool fabrics was obtained.In addition,the dyed wool fabrics have good conductivity.Thirdly,polyethylene glycol(PEG)template was introduced to investigate the laccase-catalyzed polymerization of caffeic acid and dyeing wool fabrics.The role of PEG in the polymerization of caffeic acid was examined using UV-Vis spectra;the probable structures of poly(caffeic acid)/PEG were analyzed by FT-IR and MALDI-TOF measurements.The dyeing properties,wetability and electrical conductivity of dyed wool fabric were evaluated by K/S value,contact angle and CV curve.The results show that poly(ethylene glycol)formed a complex with caffeic acid though hydrogen bonds based on the‘zip'mechanism.During the catalysis of caffeic acid by laccase,PEG template promoted the enzymatic polymerization in term of the degree of polymerization;higher K/S values and the color fastness(grades 4-5)of dyed wool fabrics were obtained.The treated wool fabrics showed good wettability and electroactivity.Fourthly,chitosan oligosaccharide(COS)was used as a template to study the polymerization of hydroquinone and the dyeing of cotton fabrics under the laccase catalysis.In order to understand the mechanism of the template-oriented enzymatic polymerization of HQ,glucosamine hydrochloride(GAH)was selected as the model compound of COS to investigate the laccase-catalyzed polymerization.Ultra High Performance Liquid Chromatography-Mass Spectrometry(UPLC-ESI-MS)was used to analyze the bonding mode between hydroquinone and GAH.The structure of poly(hydroquinone)/COS was characterized by UV-Vis,FTIR and ~1H NMR.The dyeing properties of the dyed cotton fabric were evaluated by K/S value and color fastness.E.coli was used for antibacterial test to evaluate the antibacterial effect of dyed cotton fabric.The results showed that poly(hydroquinone)was covalently bonding with COS via Schiff-base and Michael-addition reactions;brown cotton fabric was successfully achieved by intrducting chitosan oligosaccharide template;good color fastness to washing and light fastness(4-5 grades)of dyed cotton fabrics were obtained;the antibacterial properties of poly(hydroquinone)/COS dyed cotton fabrics is excellent.Finally,the effect of laccase catalyzed polymerization of hydroquinone on the dyeing properties of cotton fabrics was investigated by pre-deposition of chitosan.The polymerization of hydroquinone/chitosan under laccase catalysis was monitored by UV-vis on the absorbance of reaction solution;the dyeing process conditions of cotton fabrics using laccase catalysis of hydroquinone was optimized by K/S value;Qualitative characterization of dyed cotton fabric was carried out by FTIR,SEM,X-ray photoelectron spectroscopy(XPS).The results showed that the optimum conditions were:chitosan concentration:5 g/L,hydroquinone concentration:1 mol/L,reaction temperature:60°C,reaction time:6 h;dry rubbing fastness and soaping resistance of dyed cotton fabric Fastness(except for color fastness)can reach 4-5 grades;the oxidation resistance and UV resistance of dyed cotton fabric were improved,40%ABTS free radicals can be removed in 30 minutes,UPF value is up to 100~+. |
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