Etching and Post‐Treatment Surface Stability of Track‐Etched Polycarbonate Membranes by Plasma Processing Using Various Related Oxidizing Plasma Systems

Abstract

Oxidizing plasmas (O 2 , CO 2 , H 2 O (g), and formic acid (g)) were used to modify track-etched polycarbonate (PC) membranes and explore the mechanisms and species responsible for etching. Etch rates were measured using scanning electron microscopy; modified surfaces were characterized with X-ray photoelectron spectroscopy and water contact angle. These results were combined with optical emission spectroscopy to provide insight into etch mechanisms. Although oxide functionalities implanted were similar, H 2 O (g) and formic acid vapor plasmas yielded the lowest contact angles. The CO 2 , H 2 O (g), and formic acid (g) plasmamodified surfaces were found to be similarly stable 1 month after treatment. Etch rate correlated directly to the relative gas-phase density of atomic oxygen and hydroxyl radicals.

Evaluation of polymer hydrophobic recovery behavior following H2O plasma processing

“…H 2 O plasma‐treated PC, however, has a visible regular surface roughness consisting of small nodules (Figure d). These changes in surface morphology on PC have been noted in previous studies and are believed to be the result of redeposition of reduced carbon or differential etching associated with reduced carbon deposits that coincide with the presence of hydrogen in the H 2 O plasma system.…”

“…PC membranes were rendered wettable by the H 2 O plasma modification and this effect generally persists, showing only a small, but manageable amount of hydrophobic recovery . An expanded study looked more broadly at the mechanism of PC surface modification and etching from exposure to oxidizing plasma conditions, finding that oxygen and, to a lesser extent, hydroxyl radicals are primarily responsible for etching the PC surface. Interestingly, SEM images obtained in that study are consistent with those presented here.…”

“…H 2 O plasma modification was performed in an inductively coupled glass barrel style reactor described previously . Briefly, the induction coil is powered by a 13.56 MHz rf power generator (Advanced Energy Industries Inc., Fort Collins, CO) via a matching network, pumping is achieved using a two‐stage rotary pump (< 10 mTorr base pressure), and pressure is measured using a Baratron® capacitance manometer (MKS Instruments Inc., Andover, MA).…”

Ar/O2 and H2O plasma surface modification of SnO2 nanomaterials to increase surface oxidation

“…Thus, this plasma system may not be as effective for creating highly sensitive nanomaterials-based gas sensors. Additional oxygen containing plasmas may be further explored for their effects on SnO 2 nanomaterials, including formic acid, CO 2 , and CO, as such systems have been shown to modify polymeric membranes [20] with similar results to the Ar/O 2 plasma treated SnO 2 nanomaterials. M a n u s c r i p t M a n u s c r i p t A c c e p t e d M a n u s c r i p t M a n u s c r i p t M a n u s c r i p t …”

Innovative Applications of Surface Wettability Measurements for Plasma‐Modified Three‐Dimensional Porous Polymeric Materials: A Review

“…Whether or not this could be considered truly “hydrophilic,” however, is a debatable question. Furthermore, the extent to which a material's hydrophilicity can vary after modification (e.g., aging effects such as hydrophobic recovery, etc.) makes it difficult to claim that all materials below a specific CA value (e.g., 90°) should be broadly categorized as “hydrophilic.” Thus we support the approach of using this terminology as qualitative descriptors.…”