Laccase-catalyzed poly(ethylene glycol)-templated ‘zip’ polymerization of caffeic acid for functionalization of wool fabrics

Abstract

Abstract A cleaner approach for functionalization of wool fabrics via laccase-catalyzed polymerization of caffeic acid was developed. Caffeic acid was first polymerized to poly(caffeic acid) in the system where poly(ethylene glycol) was used as a template under the catalysis of laccase/O2. Ultraviolet–Visible spectroscopic measurements verified 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, poly(ethylene glycol) template promoted the enzymatic polymerization in term of the quantity of poly(caffeic acid) and the degree of polymerization. The data obtained from Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry and High Performance Liquid Chromatography-Electro Spray Ionization confirmed that poly(ethylene glycol) template aided the arrangement of the caffeic acid monomer, resulting in the increased degree of polymerization of caffeic acid in the laccase-catalyzed reaction. The poly(caffeic acid)/poly(ethylene glycol)-treated wool fabrics were prepared by laccase-catalyzed in-situ polymerization of caffeic acid under the same conditions. The treated wool fabrics showed good wettability and electroactivity. The results from fibre conductivity test and cyclic voltammetry showed that the wool fabric treated with poly(caffeic acid)/poly(ethylene glycol) complex was found to have better electrical conductivity. These data showed that the presence of poly(ethylene glycol) as a template in the laccase-catalyzed polymerization reaction greatly improved the characteristic of poly(caffeic acid). Moreover, higher color depth of poly(caffeic acid)/poly(ethylene glycol)-treated wool fabrics further validated the important role of the poly(ethylene glycol) as a template.