**1. Introduction**

Fibers, regardless of whether they are a natural or synthetic product, are used primarily for the production of clothing and technical fabrics. Recently, more and more attention has been paid to giving completely new properties to fabrics, such as antibacterial or photocatalytic properties, as well as properties of electrical conductivity. Electrically conductive fibers can be used in textronic products, which are multifunctional textile materials that have the features of standard textile products, but at the same time have the functions of electronic components. Electroconductive fibers, depending on their resistance, can be used as electrical connections, sensors, or electromagnetic field shielding materials. However, the mechanical properties of the electrically conductive fibers must allow their further processing in order to obtain a textile product.

Polyaniline, apart from polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene) (PEDOT), is one of the most popular conductive polymers because of its reversible redox, pH-switching, and sensing properties, and its simple synthesis [1]. However, like most of these types of materials, it has poor mechanical properties and thermal stability. Due to the fact that it is difficult to use melt techniques like extrusion, polyaniline fibers are formed only from spinning solution in a spinning process [2]. The polyaniline fibers were initially obtained from pure polyaniline, and in order to increase its electrical

conductivity it was doped with concentrated sulfuric acid during the preparation of the spinning solution. This improves the electrical conductivity, but weakens the mechanical properties of the fibers [3]. One of the solutions is to use high molecular weight polyaniline [4,5]. However, the most common solution is to combine polyaniline with other polymers to increase its mechanical strength and to facilitate its processing. For this purpose, polymers known for their high strength parameters, poly– ω-aminoundecanoyle (nylon-11) and poly-phenylene terephthalamide (Kevlar), were used in a wet-spinning process [6–9]. These fibers were characterized by a much higher mechanical strength in comparison to pure polyaniline fibers; however, they had several orders of magnitude lower electrical conductivity [2].

One of the polymers used for this purpose is also a polyacrylonitrile, which is characterized by high mechanical strength, as well as thermal and chemical resistance, and also low price. In addition, it is a fiber-forming polymer popularly used for the production of carbon fibers.

Zhai et al. obtained flexible and conductive layers as a result of direct polymerization of aniline on the surface of microporous polyacrylonitrile. The use of PAN improved the mechanical properties and thermal stabilities of the polyaniline layers [10]. The combination of PAN and PANI polymers is used in medicine, where copolymer is used as scaffolds for muscle cells [11]. Polymer membranes were made from the PANI-doped polyacrylonitrile, and their color depended on the pH of the solution [12]. Moreover, fibers from the PAN/PANI composition were made by electrospinning, where an increase in electrical conductivity towards polyacrylonitrile was observed [13]. Toptas et al. obtained conductive polyaniline/polyacrylonitrile composite fibers by sorption of aniline and polyacrylonitrile fiber [14]. These fibers had satisfactory electrical conductivities, mechanical strengths, and resistances for laundering. Xia and Lu obtained conductive fibers in which polyacrylonitrile fibers were coated with polypyrrole, polyaniline, and poly (3,4-ethylenedioxythiophene). The polymerization occurred directly on the surface of the PAN fibers, by way of a chemical connection between polyacrylonitrile chains and conjugated polymers that was created [15]. There are also studies in which polyaniline fibers are doped with carbon nanotubes (CNT) with high electrical conductivity and high mechanical strength [16].

This article presents the results of research on PAN/PANI fibers, obtained using the wet method, from solutions in which the polymer matrix was polyacrylonitrile (PAN) and admixed polyaniline (PANI). PANI was introduced to PAN fibers using two methods:


The present method, where polyaniline is synthesized in situ during the preparation of a spinning solution for forming PAN/PANI composite fibers by wet spinning, is new and has not been described in literature.
