Deposition of functional organic thin films by pulsed plasma polymerization: A joint theoretical and experimental study

The pulsed plasma polymerization of allylamine and cyclopropylamine is investigated to study the influence of the precursor chemical structure on the process selectivity toward the primary amine groups. Both systems are compared under similar mean powers injected in the discharges (P_mean). The results reveal an increase in the precursor fragmentation in the plasma and a decrease in the primary amine content of the film (%NH₂) as P _mean increases. Nevertheless, below a critical P_mean value, different behaviors are observed depending on the precursor, cyclopropylamine being less plasma-fragmented than allylamine. As a result, plasma polymer films (PPF) synthesized from cyclopropylamine yield the largest %NH₂. These results are rationalized with the help of theoretical calculations pointing to a preferential opening of the cyclopropylamine ring structure. Cyclopropylamine activation in the plasma can thus be achieved without fragmentation reactions, leading to a more efficient incorporation of the -NH₂ group of the precursor in the PPF.