Role of plasma polymerization conditions in forming unsaturated and aromatic bonds and free radicals

Plasma polymers (PPs) films are deposited from a complex environment created by dissociating the original gas feed. Thus, their chemical structure cannot be derived only from the starting reactants. It depends on the electron concentration and energy given by the discharge parameter. The deposition is also influenced by the collision frequencies related to the pressure and the energy flux transmitted by ions accelerated within the plasma sheath adjacent to the substrate. We studied the plasma polymerization of cyclopropylamine (CPA) mixed with Ar in radio-frequency (RF) capacitively coupled plasma (CCP) at different plasma conditions because the resulting amine PPs could be used as a functional layer immobilizing the antibodies in immunosensors or as hydrophilic positively charged layer suitable for cell adhesion and proliferation. However, the former application can be used as a sensitive probing method that reveals the importance of unsaturated carbon-nitrogen bonds for film reactivity. The presence of free radicals can also mediate the film reactivity. Therefore, I will discuss the relation of the plasma conditions, including the role of discharge pulsing, on all these film structural properties beyond the hunt on high nitrogen and amine-groups content in bioactive amine PPs.