Structural characterization and mechanical properties of functionalized pulsed-plasma polymerized allylamine film

Due to its surface properties, especially the presence of abundant amine groups, pulsed-plasma polymerized allylamine (PPAa) is used to manufacture biosensor and modify surface of metallic biomaterials. In the present study, PPAa films on 316L medical stainless steel are prepared by pulsed radio frequency (RF) plasma polymerization using allylamine as a precursor under different duty cycles. The effect of the pulsed duty cycles on the composition, structure, surface morphology, wettability and mechanical properties of PPAa films are investigated by Fourier transform infrared (FTIR) spectroscopy, laser Raman spectra, X-ray photoelectron spectroscope (XPS), atom force microscope (AFM), contact angle measurement, nanoscratch test and substrate straining method. All results of FTIR, XPS and Raman indicate that there are more amine groups from allylamine monomer on the 20/80 film fabricated by 20% duty cycle. The wettability of the 20/80 film is higher than that of 20/30 film prepared using 40% duty cycle. AFM micrographs demonstrate no remarkable differences in the morphological characteristics, but grain size of 20/30 film is larger than that of 20/80 film. The critical force of 20/80 film is about 71.86 mN, higher than that of 20/30 film and has a better scratch resistance. It is estimated that the mechanical properties of the plasma polymerization are different.