Synthesis and characterization of poly (acrylonitrile-co-acrylic acid) as precursor of carbon nanofibers

Synthesis of a co-polymer of polyacrylonitrile (PAN) producing a carbon nanofiber out of PAN and co-polymer of PAN and comparison between these products were examined. Free-radical solution copolymerization of acrylonitrile (AN) with acrylic acid (AA) was studied. In this perspective, AA, and AN were used as a precursor for polymerization reactions; then copolymers were synthesized by using ammonium persulfate (APS) as an oxidant and carried in water/dimethylformamide (DMF) mixture. These polymers were used to obtain corresponding electrospun nanofibers. Synthesized P(AN-co-AA) was investigated by Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) spectroscopy, and characteristic peaks for AN unit, AA were achieved. Thermal behavior was examined by using differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA), and results indicated that addition of monomers to AN unit reduced the Tg value of homopolymer PAN compared to P(AN-co-AA), which provides improvement to the cyclization and the formation of a thermally stable aromatic ladder polymer chain formation. In order to prevent the shrinkage and maintain the molecular orientation on nanofiber webs during stabilization, tension was applied to the samples, and thermal oxidation varies at 200-300 degrees C for different duration of times. Surface morphology of the fibers was observed with scanning electron microscope (SEM), and average nanofiber diameter was found 550nm, and after carbonization it was reduced to 320nm for homopolymer PAN, and for poly(AN-co-AA) average nanofiber diameter was found as 220nm and reduced to 130nm, respectively. Copyright (c) 2016 John Wiley & Sons, Ltd.