Study On Surface Grafting Modification Of Wool Based On Disulfide Bonds

Wool fiber,a natural protein fiber,has been popular in consumers due to its softness,strong warmth,good elasticity and wear resistance.There also are many disadvantages of wool fiber,such as,easy felting,surface-hydrophobicity,and static electricity due to its special scale structure and dense lipid film on the surface.In order to solve these problems,physical,chemical and biological methods were applied to modify wool.However,these techniques usually lead to poor durability,residual toxic substances,damage to material matrix,deterioration of physical properties like handle and color,and also other issues.Considering that wool is a keratinous material,rich in cysteine residues and contains disulfide linkages（-S-S-）,the disulfide bonds can be broken and form active thiol groups,after reduction pretreatment.The thiol groups can react with thiol groups or olefin in molecular structure of functional compounds providing a convenient way for functional modification of wool and other keratin-containing materials.In this paper,wool fabric was modified with chitosan through disulfide bond breakingand reforming reactions to investigated the feasibility of grafting modification of wool through thiol groups;wool fibers were reduced to create thiol groups and then grafted with MPEGMA through a horseradish peroxidase（HRP）-mediated thiol-ene click reaction to improve the hydrophilicity of the fiber;wool fibers were grafted with 3-（trimethoxysil）propyl methacrylate（MEMO）through HRP enzymatic thiol-ene click reaction,and then covered with dimethyloctadecyl[3-（trimethoxysilyl）propyl]ammonium chloride（QUAT）to finish wool with sol-gel.The study provides a novel and convenient approach to modify wool and other keratin-containing materials,for good durability,little damage,and can flexibly to obtain a variety of functions.It can diversify the modification methods of wool and other keratin-containing materials,and broaden the application of materials in related fieldsFirstly,glutathione was chosen as the model compound for wool to couple with thiolated chitosan,and the molecular structure of the product was analyzed by Fourier transform infrared spectroscopy（FT-IR）and nuclear magnetic resonance spectroscopy(¹³C-NMR)to analyze the feasibility of reconstructing disulfide bonds.Thiolated chitosan was grafted to fiber surface through breaking and reconstruction of the disulfide bonds.The scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）,and X-ray diffraction（XRD）were used to analyze the surface morphology and structural changes of modified wool fibers.The physical and mechanical properties,dyeing properties,felting properties and antibacterial properties of wool fabrics were tested.The results show that thiolated chitosan can be coupled with glutathione through disulfide bonds.The graft ratio of thiolated chitosan modified wool fabric is 3.65%,the area shrinkage is 2.06%.The modified fabric obtained a better anti-felting property.The contact angle of modified wool fabric is115.44°and the wetting time was reduced to 9.58 min,and the hydrophilic property was improved.Compared with untreated wool fabric,the antibacterial properties of modified wool fabrics have also been improved with a bacteriostatic rate of 58.32%.Secondly,HRP enzymatic the thiol-ene click chemical reaction was used to functional modify wool.L-cysteine was selected as the model compound for wool fiber and coupled with MPEGMA.The molecular structure of the product was analyzed by FT-IR and Matrix-assisted laser-desorption/ionization time-of-flight mass spectra（MALDI-TOF MS）to investigate the feasibility of enzymatic reaction.Then,MPEGMA was grafted onto the surface of wool fiber,confirmed by SEM,XPS and Raman spectroscopy.The results show that L-cysteine can be coupled with MPEGMA through the thiol-ene click reaction.Compared with the untreated wool fabric,the MPEGMA graft modified wool fabric is completely hydrophilic,and the contact angle is reduced to 0°.the density of modified wool fiber shrinkage ball is reduced to 0.043 g/cm³,and the modified wool fibers obtain good anti-felting properties;Moisture permeability and moisture regain have also been improved,and it still maintains a good performance after 10 times machine washings.Finally,HRP/H₂O₂ was used to enzymatically catalyze the thiol-ene click reaction,and MEMO was grafted onto the surface of the wool fiber.The graft reaction was confirmed by means of energy dispersive X-ray（EDX）and the weight gain rate of the fabric.After grafting modification,the wool fabric was covered with QUAT under acidic conditions to form a sol-gel coating on the surface of the wool fiber.The surface morphology and structural changes of the wool fiber were analyzed by SEM and XPS.The physical and mechanical properties,surface wetting properties,felting properties and antibacterial properties of the modified wool fabric were investigated.The results show that there is no obvious change in the hydrophilicity of wool fabrics treated with sol-gel and contact angle is 123.44°.The density of modified wool fiber shrinkage balls is 0.039 g/cm³,and the bacteriostatic rate is 60.72%.The modified wool fibers obtain good anti-felting and antibacterial properties.