The influence of pulse parameters on film composition during pulsed plasma polymerization of diaminocyclohexane

Plasma polymerization of diaminocyclohexane was investigated in order to deposit the amine groups rich plasma polymer films for biomedical applications. The obtained films were characterized by FTIR and XPS in dependence on duty cycle ranging from continuous wave mode (CW) to 0.1 and ton varied from 0.02 to 10 ms. The concentration of primary and secondary amine groups was determined by the derivatization technique using trifluoromethyl benzaldehyde (TFBA) and trifluoroacetic anhydride (TFAA). It has been shown that the concentration of both follows the same curve with the minimum at ton=0.5 ms (duty cycle 0.1). The plasma polymerization process likely differs here from the processes for higher and lower ton. The highest primary amine concentration reached is 8%. The films prepared at ton=0.5 ms are shown to be less stable due to aging by oxidation as shown by XPS on films kept in open air. The FTIR analysis confirms the same dependence of amine groups’ concentration as above. As the deposition rate increases for decreased ton it will be advantageous to prepare the plasma polymer films with the higher amine group concentrations at decreased ton below 0.5 ms.