Poli(m-fenilendiamin-ko-m-aminobenzoik asit) kopolimerinin sentezi ve spektroskopik özelliklerinin incelenmesi = Synthesis, doping and spectroscopic properties of poly(m-phenylenediamine-co-m-aminobenzoic acid) copolymer

Abstract

Copolymers contain the properties of homopolymers of their constituent monomers and are synthesized to improve the solubility and processability of homopolymers. Poly(m-phenylenediamine) (PmPDA) and poly(m-aminobenzoic acid) (PmABA) are among the derivatives of the conductive polyaniline polymer. Phenylenediamine polymers started with polyaniline. Polyaniline, one of the most studied conductive polymers, stands out due to its conductivity, redox activity and sensitivity. Standard polyaniline is available in conductive and semiconductor forms. Redox activity refers to the polymer's ability to be oxidized or reduced. These properties are used in energy conversion and corrosion protection. With its pH-dependent transition from a conducting polyaniline salt to a non-conducting base, polyaniline demonstrates the ability to respond to external stimuli through change in conductivity or color, a valuable property in sensors. Poly(m-phenylenediamine) homopolymer has low solubility in common organic solvents. To improve the properties of P(mPDA) and provide different functionalities, various copolymers of m-phenylenediamine (mPDA) have been synthesized by many researchers. Li et al. [2003] synthesized soluble copolymers using m-phenylenediamine and o-ethoxyaniline at different monomer ratios. Zoromba et al. [2009] synthesized and characterized poly(o-aminophenol-co-m-phenylenediamine) copolymer as a copolymer by mechanochemical solid state polymerization and interfacial polymerization methods. They found the band gap energies for copolymer samples obtained by mechanochemical and interfacial methods to be 2.19 eV and 2.09 eV, respectively. Poly(m-phenylenediamine-co-aniline) [Hosny, et al.,2018] and poly(m-phenylenediamine-co-anthranilic acid) P(mPDA-co-ANTH) [Hosny, et al.,2019]. The copolymers of m-phenylenediamine and o-anisidine were synthesized by Melad and Hilles [2024] using oxidative polymerization. On the other hand, aniline and m-aminobenzoic acid copolymers were synthesized by some researchers [Adhikari and Banerji, 2013; Jokić et al., 2017; Hrichi et al., 2017; Thiemann and Brett, 2001]. Poly(m-phenylenediamine-co-m-aminobenzoic acid) (PmPDA-co-mABA) copolymer has amine, imine, quinoid, phenazine and carboxylic acid functions. Carboxylic acid functionality in this copolymer, self-doping into poly(m-phenylenediamine) polymer, metal ion chelation, optical properties, etc. In this study, P(mPDA-co-mABA) copolymer was synthesized by chemical oxidation method using ammonium persulfate. In addition, poly(m-aminobenzoic acid) (PmABA) and poly(m-phenylenediamine) (PmPDA) homopolymers were also synthesized in the present work. The properties of P(mPDA-co-ABA) copolymer were analyzed comparatively with poly(m-phenylenediamine) (PmPDA) and poly(m-aminobenzoic acid) (PmABA) homopolymers. Synthesized poly(m-phenylenediamine) (PmPDA) and poly(m-aminobenzoic acid) (PmABA) homopolymers and P(mPDA-co-ABA) copolymer were characterized using FT-IR, UV-vis. absorption, fluorescence (FL) emission, SEM, XRD and MALDI-TOF-MS spectroscopy methods. UV-vis. absorption spectra of the PmABA, PmPDA and P(mPDA-co-mABA) polymer solutions in NMP solvent were taken. In the absorption spectrum of the PmPDA polymer, the absorption bands were observed with a maximum at 281 nm and a shoulder at 380 nm. The absorption profile of the PmFDA extends up to 640 nm in the visible region. The PmABA polymer showed an absorption spectrum with maxima at wavelengths of 294 nm and 380 nm. The absorption of the PmABA polymer extends to 840 nm wavelength. The absorption spectrum of the P(mPDA-co-mABA) copolymer resulted in a different absorption profile than the PmPDA and PmABA homopolymers. For the P(mPDA-co-mABA) copolymer, the maximums of the absorption bands were observed at 294 nm and 380 nm, and the absorption spectrum was observed to extend up to approximately 840 nm. The absorption bands at 280 –294 nm for the PmABA, PmPDA, and P(mPDA-co-mABA) polymers were attributed to the π–π* transition of benzenoid rings. The absorptions at approximately 380 nm wavelengths are n-π* transitions, and the higher absorption bands are due to polaron-π* and π-polaron transitions. The PmPDA and PmABA homopolymers and the P(mPDA-co-ABA) copolymer were doped with Cu(II), Fe(III) and I2 redox reagents. The synthesized homo polymers and the copolymer doped with Cu(II), Fe(III) and I2 were examined by UV-vis. absorption spectroscopy and FL emission spectroscopy methods. The direct and indirect band gap energies (Eg) were calculated from the UV-vis. absorption data of the polymers doped and undoped with Cu(II), Fe(III) and I2. The direct band gap energy of the PmABA polymer was found to be 1.96 eV, and the indirect band gap energy was 1.54 eV. It was determined that the direct band gap energy of the PmPDA polymer was 2.62 eV and the indirect band-gap energy was 1.90 eV. The direct band gap energy of the P(mPDA-co-PmABA) copolymer was obtained as 2.32 eV, and the indirect band gap energy was 1.78 eV, which are between the values of the homo polymers. It was observed that the band gap energies of the P(mPDA-co-ABA) copolymer decreased upon doping with Cu(II), Fe(III) and I2. The synthesized PmABA, PmPDA and P(mPDA-co-mABA) polymers were examined by FL spectroscopy, and it was observed that the PmABA emitted blue FL emission under UV light, and the PmPDA and P(mPDA-co-mABA) polymers emitted turquoise (blue-green) color FL emission. The binding Ka equilibrium constants of Cu(II), Fe(III) and I2 doping reagents to the PmABA, PmPDA and P(mPDA-co-mABA) polymers were examined by the FL emission quenching method. The binding Ka equilibrium constants were calculated using the Stern-Volmer, and Modified Stern-Volmer equations. The binding equilibrium constants (Ka) of Cu(II), Fe(III) and I2 doping reagents to the PmABA polymer were found to be 4.39 x 102, 2.43 x 1011 and 1.54 x 103 M-1, respectively. The binding Ka constants of Cu(II), Fe(III) and I2 for the PmPDA polymer were found as 5.28 x 107, 1.40 x 107 and 1.06 x 1014 M-1, while for P(mPDA-co-mABA) copolymer binding Ka constants were found to be 1.09 x 103, 5.93 x 108 and 9.75 x 1013 M-1, respectively. High binding constants has been observed for the binding of Fe(III) to PmABA, the binding of Cu(II), Fe(III) and I2 to PmPDA, and the binding of Fe(III) and I2 to the P(mPDA-co-mABA) polymer. Cu(II), Fe(III) and I2 additives are redox active and chelating materials, and it was expected that both the redox and chelating mechanisms can be effective in binding them to polymers. From the binding constants, it can be concluded that the carboxylic acid group is effective in the binding of Fe(III) additives, while the amine groups are effective in the binding of Cu(II), Fe(III) and I2 additives.In the FE-SEM images, it was observed that the PmABA homopolymer had a nanoporous structure with particle sizes of 0-15 µm and 0-400 nm. The PmPDA homo polymer was determined to have regular and spherical shaped particles with particle sizes of 0-900 nm. The P(mPDA)-co-mABA) copolymer was also observed to have regular and spherical shaped particles with sizes in the range of 0-800 nm. From XRD analyses, it was seen that the PmPDA homo polymer has more amorphous properties. It has been observed that PmABA homopolymer and P(mPDA-co-mABA) copolymer have a high crystal phases. From MALDI-TOF-MS analyses, it was found that the average molecular weight (Mn) of the P(mPDA-co-mABA) copolymer was 2263 Da and the molecular weights ranged up to 5500 Da. As a result, the P(mPDA-co-mABA) copolymer binds Fe(III) and I2 at high rates, and it is thought that Fe(III) and I2 doped P(mPDA-co-mABA) copolymer will be a material with potential in light absorption, fluorescence emission and electrochemical fields.