Synthesis and Characterization of Polyaniline, Poly(3-fluoroaniline), and Poly(aniline-co-3-fluoroaniline) Derivatives Obtained by Chemical Oxidative Polymerization Methods

ABSTRACT

The syntheses of thermally stable, conducting polyaniline, poly(3-fluoroaniline), and poly(aniline-co-3-fluoroaniline) derivatives by chemical oxidative polymerization methods are described. By varying the mol% of 3-fluoroaniline in the monomer feed, a series of new poly(aniline-co-3-fluoroaniline) derivatives with different chemical compositions were prepared by chemical oxidative copolymerization methods using ammonium persulfate as oxidant in the presence of hydrochloric acid as the dopant. The chemical oxidative copolymerization of aniline with 3-fluoroaniline affords poly(aniline-co-3-fluoroaniline) derivatives with increased solubility properties, greater thermal stability, improved morphological control, and enhanced electrical characteristics, which promotes the processibility of the different fluorine-functionalized polyaniline derivatives when compared with the parent polyaniline homopolymer.

Poly(3-fluoroaniline) and the different poly(aniline-co-3-fluoroaniline) derivatives show better solubility and thermal stability than the polyaniline homopolymer, due to the incorporation of the F atoms along the fluorine-functionalized polyaniline backbone. Furthermore, the poly(3-fluoroaniline) homopolymer is thermally more stable than the polyaniline homopolymer due to the presence of the C–F bonds of the 3-fluoroaniline units along the polymer backbone. The electrical conductivity of the different poly(3-fluoroaniline) derivatives is dependent on the 3-fluoroaniline content in the polymer derivative and the morphology of the specific copolymer. The poly(3-fluoroaniline) homopolymer exhibits the lowest electrical conductivity. In addition, the electrical conductivity of the different poly(aniline-co-3-fluoroaniline) derivatives decreases with increasing 3-fluoroaniline content in the copolymer. The different polymer derivatives were characterized by proton nuclear magnetic resonance (¹H NMR) spectrometry, fourier transform infrared (FTIR) spectroscopy, ultraviolet visible (UV–Vis) spectroscopy, thermogravimetric analyses, scanning electron microscopy, and electrical conductivity measurements.

GRAPHICAL ABSTRACT

KEYWORDS:

• Electrical conductivity
• morphology
• poly(aniline-co-3-fluoroaniline)s
• poly-3-fluoroaniline
• polyaniline
• thermal stability

Acknowledgments

Funding from the University of South Africa, Pretoria, South Africa and Qatar University, Doha, Qatar is gratefully acknowledged. Mohd Rashid thanks the Department of Chemistry, College of Natural Sciences, Wollo University, Ethiopia for providing the necessary research infrastructure.