Structural and Morphological Properties of Free Base Porphyrin Doped Colored Electrospun Polyvinyl Alcohol and Polyacrylonitrile Nanofibers

Although there have been many recent studies on the functional applications of cluster-based polyacrylonitrile (PAN) polymer nanofibers (NFs), there are few studies on their color properties. In this study, polyvinyl alcohol (PVA) and PAN polymers were doped with 5,10,15,20-tetra(4-tert butylphenyl)porphyrin, free base porphyrin derivative, respectively, and PVA-porphyrin (PVA-P) and PAN-porphyrin (PAN-P) NFs were produced by electrospinning. The morphological and structural properties of the obtained NFs were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. NFs were also evaluated according to their colors. The analyses demonstrated that the porphyrin monomers in the electrospun NFs bonded to PAN more successfully than PVA. Porphyrin-doped PAN NFs produced under different optimization conditions exhibited different color tones as a result of electrospinning, and FTIR analysis results also supported the color analysis results. It was observed that PAN-P and PAN-P2 NFs exhibited the most successful cross-linking to the polymer with the characteristic peaks of porphyrin at 802 \(\:{cm}^{-1}\) and 803 \(\:{cm}^{-1}\), respectively. Furthermore, it was observed that as the applied voltage during electrospinning increased, more porphyrin molecules were deposited onto the fiber surface of PAN. This phenomenon can be attributed to the electrostatic force applied to the porphyrin molecules. Additionally, PAN-P NFs to which a relatively higher voltage value was applied exhibited a darker color than PVA-P NFs. It is postulated that the colored NFs, a novel material produced and introduced to the literature in this study and doped with free base porphyrins, may have the potential to be utilized in applications related to colorimetric and electrochromatic sensors in future studies.