Polyimide Film Surface Modification by Nanosecond High Voltage Pulse Driven Electrical Discharges in Water

Abstract

Nanosecond high voltage pulses of 10 ns duration were used to generate pulsed discharges in distilled water for surface modifications of the aromatic and partially aromatic polyimides. Optical emission spectroscopy has shown the formation of excited speciesin plasma due to water dissociation and ionization. Molecular bands of hydrogen, oxygen, and nitrogen have dominated the emission spectra. The reactive species are likely to be responsible for the observed surface modifications of polymer films which were investigated by FTIR, AFM, XPS, and static contact angle measurements. The surface hydrophobicity of the polyimide films increased with treatment time. The mechanism of surface modification of polyimides treated by nanosecond pulsed discharges was different from previously described interactions with plasmas that were generated with microsecond voltage pulses. Nanosecond high voltage pulses have induced an increase of the unsaturated bondings on the polyimide surface, while the segregation of CF 3 groups at the film surface was responsible for the increased surface hydrophobicity when discharges were generated with microsecond high voltage pulses.

Optical properties of polyimides films treated by nanosecond pulsed electrical discharges in water

“…The details are presented in our previous works. 15,19) High-voltage pulses were applied with a commercial nanosecond generator (FID Technology FPG 150-1NK). The pulse generator can deliver positive high-voltage pulses of rectangular shape with a duration of 10 ns (FWHM) and a rise time of 3 ns to a load of 50 Ω.…”

“…Figure 2 displays representative FTIR spectra of PI=CoCl 2 hybrid films (10% CoCl 2 ) in comparison with those of untreated and plasma-treated films for different periods of time (10,15, and 20 min). Thus, the characteristic imide ring absorptions appeared in the FTIR spectra at 1720-1725 cm −1 (symmetrical C=O imide stretching) and around 1375 cm −1 (C-N-C axial stretching), demonstrating the preservation of the polyimide cycle.…”

“…The slight blue shift of the emission spectra may be the consequence of the UV radiation formed in plasma, 15) which effectively induced the modification at the intramolecular level. The excited species may induce a random hemolytic cleavage of bonds in the main chain, resulting in new structures, such as 2,3-dihydro-1,4-phthalazinedione.…”

“…19) Shock waves are generated in plasma. 15,16) It is well known that the variation in pressurization affects the intermolecular and intramolecular CT transitions.…”

Enduring and Stable Surface Dielectric Barrier Discharge (SDBD) Plasma Using Fluorinated Multi-Layered Polyimide

“…In recent years, several groups have modified polymers' surface chemical composition with the help of plasma in order to increase their adhesion or hydrophilicity [24][25][26][27]. During plasma processing, ion bombardment breaks chemical bonds in the polymer's backbones, while radicals enable functional groups to be grafted onto the polymer's surface.…”