DC pulsed plasma surface treatment of polystyrene thin films with nitrogen:: study of the correlation between energy distribution and wettability

A systematic study was carried out in order to characterise a DC pulsed discharge used for the treatment of polystyrene thin films. The energy which is injected into plasma can be modulated while exploiting the discharge time (tau), the afterglow duration time (t(ag)) and the treatment duration time (t(t)). The variations of the macroscopic properties of surface were monitored by measurement of the contact angle and we correlated these results of wettability with the way in which energy is distributed. The experimental results showed that the surface treatment was better (the largest wettability) for the smallest values of tau (2 mus) and largest times of t(ag) (0.1 s). A sensitivity of the treatment to the distribution of energy was highlighted, and it is through this study that we will put forth assumptions on the species responsible for the treatment.