A poly(m-phenylene diamine) (PmPDA)/sulfonated single-walled carbon nanotubes (SWCNT-SO3H) nanocomposite was synthesized via in situ polymerization. Successful incorporation of SWCNT-SO3H into the PmPDA matrix was confirmed through Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, UV-visible spectroscopy, and thermogravimetric analysis. The nanocomposite exhibited a red shift of 6 nm in the UV-visible spectrum compared to the pristine polymer, attributed to the conductivity of the incorporated nanotubes. The thermogravimetric analysis also showed improved thermal stability for the nanocomposite over the polymer. Importantly, the nonlinear optical properties were studied via Z-scan measurements. The nanocomposite displayed a nonlinear refractive index on the order of 10−3 m2/W and a nonlinear absorption coefficient on the order of 10−5 m/W, demonstrating self-defocusing behavior. Varying the concentration from 0.3 to 0.7 mg/mL and input laser intensity from 6.2 to 164.5 mW/cm2 tuned the optical nonlinearity. Overall, the easy integration of carbon nanotubes makes the PmPDA nanocomposite a useful self-defocusing material for optical limiting and switching applications.
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