Abstract
Laccase-mediated systems are a green route to accelerate the oxidation of aniline and obtain polyaniline with conductive properties. The synthesis of green polyaniline (emeraldine salt) was herein improved by the inclusion of additives like sodium bis (2–ethyl hexyl) sulfosuccinate (AOT) and potassium hexacyanoferrate (II) (KHCF) in the medium. The aniline polymerization was confirmed by the detection of the absorption band typical of emeraldine salt at 420 nm, typical of the semiquinoid radical cation, and of the polaron absorption band at 700–800 nm, corresponding to the distinctive signal of doped or partial doped aniline. The oligomers and/or polymers obtained were characterized by spectrometry techniques, namely 1H NMR and MALDI-TOF, and the bacterial cellulose (BC) conductivity was assessed by means of a four-point probe electrical conductivity technique. The best polymerization results were obtained with 5 mM AOT, 10 mM KHCF, and 25 U/mL of laccase. The synergistic effect between both additives in the presence of a catalyst leads to obtaining BC samples coated with green polyaniline with promising electric conductive properties.
Highlights
Bacterial cellulose is a versatile biopolymer produced by Acetobacter xylinum with exceptional properties, like high purity, high porosity, high permeability to liquid and gases, high water-uptake capacity, tensile strength, and an ultrafine network
Despite the low redox-potential of Mtl, this catalyst was chosen for the oxidation and the experiments were conducted for longer periods of time than that it would be necessary if a high-redox potential was used
We examined different media containing an anionic surfactant AOT and a radical initiator, KHCF, to function as (i) a template facilitating the p-directed coupling of the monomers, (ii) as an anionic dopant to obtain conductive PANI, and (iii) to improve the polymer solubility in water by micelles aggregation
Summary
Bacterial cellulose is a versatile biopolymer produced by Acetobacter xylinum with exceptional properties, like high purity, high porosity, high permeability to liquid and gases, high water-uptake capacity, tensile strength, and an ultrafine network. Bacterial cellulose has been explored as a template for the in situ polymerization of a panoply of compounds from phenols to polyamines. An example has been reported by Song et al who studied the in situ polymerization of several flavonoids by laccase onto a bacterial cellulose support (Song et al, 2018). The usage of bacterial cellulose as a template for aniline polymerization has been undertaken. Lee et al studied the preparation of bacterial cellulose/polyaniline composite films by chemical oxidative polymerization of aniline (Lee et al, 2012). Aiming to enhance the electrical conductivity of bacterial cellulose, this material was coated with conductive polymers (Xu et al, 2013; Jasim et al, 2017). Different oxidizing agents have been explored on the production of polyaniline coated
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