The role of ions in the plasma polymerization of allylamine

The radio-frequency-induced plasma polymerization of allylamine has been investigated in the plasma-gas phase by mass spectrometry and at the plasma-solid interface by means of an ion flux probe and a quartz mass balance. The surface chemistry of the deposits has been determined by X-ray photoelectron spectroscopy. The objective of this study was to unravel the mechanism(s) by which allylamine plasma polymers form. The results are compared with those obtained in an earlier investigation of the plasma polymerization of acrylic acid. In the plasma-gas phase, evidence is provided for reactions: between cations and intact neutral monomers (allylamine). These oligomerization reactions were found to be relatively power-insensitive compared with those seen in plasmas of acrylic acid, as was the gas-phase concentration of the intact neutral monomer. At the polymer surface, ion fluxes were found to increase with plasma input power (P) from 6.6 x 10(16) ions m(-2) s(-1) at 1 W to 1.4 x 10(18) ions m(-2) s(-1) at 14 W. The ionic mass transport to the polymer surface lion mass flux) was calculated by multiplying the measured ion flux by the average ion mass (determined by mass spectrometry). At P = 1 W, the ion mass flux was 11.7 mum m(-2) s(-1), and at 14 W, the ion mass flux was 226.6 mum m(-2) s(-1). These values differed from the total mass deposition rates measured by the quartz mass balance, which were 18.7 and 127.1 mum m(-2) s(-1), respectively. However, the relationship found between the ion mass flux, the mass deposition rate, and P was complex, and it is shown that, at very low P (<1 W), the ion mass flux is sufficient to account for all of the deposit.