Doped polyacrylonitrile fibres as UV radiation sensors

• New polyacrylonitrile fibres (PAN) were developed as UV sensors.
• UV sensitive dopants were used in PAN fibres: TTC, HHEVC and PENTA.
• UV radiation is detected through colour change of PAN fibres.
• UV dose sensitivity and dose range of PAN depend on dopants used.
• Two types of doped PAN made: glossy and lustreless, are of different characteristic.

In this work a method of preparing UV-sensitive fibres is presented. The fibres are made of polyacrylonitrile by wet spinning and 2,3,5-triphenyltetrazolium chloride (TTC), 4,4′,4″-tri-di-β-hydroxyethyloaminotriphenyloacetonitrile (HHEVC) and 10,12-pentacosadiyonic acid (PENTA) are used as dopants. Preparing the fibres is a two-step process, allowing for the preparation of two kinds of fibres with different characteristics: glossy and lustreless. When the fibres are UV irradiated they change colour, to yellow for TTC and blue for HHEVC. Those with the PENTA dopant undergo a complex colour change since at lower doses blue colour formation is initiated but at higher absorbed doses a red colour appears that finally leads to a brown colour in the fibres. The colour formation and its intensity are related to the absorbed dose and the wavelength of UV radiation. The fibres possess different morphologies and mechanical properties that depend on the preparation method. XRD analysis revealed a distinct difference between the glossy and lustreless fibres in that the former are of higher crystallinity that translates into better mechanical properties of the fibres. The impact of the dopants on the crystallinity and mechanical properties of the fibres is also discussed. One possible application of the fibres is for UV absorbed dose detection. Nevertheless, they were designed to serve as elementary units to be further manufactured into a flat textile as a 2D radiation dosimeter.