Full‐Thickness Characterization of Plasma Polymerized Hexane Films Irradiated by an Electron Beam

Pedersen, Rasmus H.; Scurr, David J.; Roach, Paul; Alexander, Morgan R.; Gadegaard, Nikolaj

doi:10.1002/ppap.201100067

Cited by 9 publications

(4 citation statements)

References 27 publications

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“…A hypothesis is that radicals still present in the vertical gradient structure, mostly migrating up from the cross-linked subsurface layer close to the vertical gradient structure, react with ambient air, thereby modifying the surface by oxidation and hydrolysis, as was also mentioned in the literature . Generally, the PPF deposited with a lower CO 2 /C 2 H 4 ratio contains more radicals, but its polymer segments are less mobile due to a higher cross-linking density, , except for the near-surface layer, which retains higher mobility due to less cross-linking. , For the reference highly cross-linked layer, where we would expect a higher WCA, the higher amounts of radicals react with ambient air resulting in a lower initial WCA, coinciding with the WCA for the vertical gradient structures and the reference oxygen-rich layer (Figure b). The long-term increase of WCA for the reference coatings then is probably due to hydrophobic recovery, where the reference oxygen-rich layer reaches the final WCA values more slowly due to the subsurface reservoir of polar groups and ongoing reorientation and migration.…”

Section: Resultsmentioning

confidence: 86%

Composition and Stability of Plasma Polymer Films Exhibiting Vertical Chemical Gradients

et al. 2017

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Controlling the balance between stability and functional group density in grown plasma polymer films is the key to diverse applications such as drug release, tissue-engineered implants, filtration, contact lenses, microfluidics, electrodes, sensors, etc. Highly functional plasma polymer films typically show a limited stability in air or aqueous environments due to mechanisms like molecular reorganization, oxidation, and hydrolysis. Stabilization is achieved by enhancing cross-linking at the cost of the terminal functional groups such as -OH and -COOH, but also -NH, etc. To overcome such limitations, a structural and chemical gradient was introduced perpendicular to the surface plane; this vertical gradient structure is composed of a highly cross-linked base layer, gradually changing into a more functional nanoscaled surface termination layer. This was achieved using CO/CH discharges with decreasing power input and increasing gas ratio during plasma polymer deposition. The aging behavior and stability of such oxygen-functional vertical gradient nanostructures were studied in air and in different aqueous environments (acidic pH 4, neutral pH ≈ 6.2, and basic pH 10). Complementary characterization methods were used, including angle-resolved X-ray photoelectron spectroscopy (ARXPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) as well as water contact angle (WCA) measurements. It was found that in air, the vertical gradient films are stabilized over a period of months. The same gradients also appear to be stable in neutral water over a period of at least 1 week. Changes in the oxygen depth profiles have been observed at pH 4 and pH 10 showing structural and chemical aging effects on different time scales. The use of vertical gradient plasma polymer nanofilms thus represents a novel approach providing enhanced stability, thus opening the possibility for new applications.

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Section: Resultsmentioning

confidence: 86%

Composition and Stability of Plasma Polymer Films Exhibiting Vertical Chemical Gradients

et al. 2017

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“…Simply layering multiple ppHex films before etching resulted in a poor quality etch. It is assumed that the film composition, in terms of oxygen/carbon, ratio is modified by exposure to atmospheric conditions,30, 31 which may result in variations in spatial selectivity and thus an inhomogeneous etch. Atomic force microscopy (AFM) analysis of the replica surface in the etched region (in groove) and the masked region (on ridge) showed an root‐mean‐square (RMS) roughness of 4.5 and 1.3 nm, respectively.…”

Section: Resultsmentioning

confidence: 99%

A Dual Gradient Assay for the Parametric Analysis of Cell–Surface Interactions

Reynolds

Pedersen

Riehle

et al. 2012

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Cellular response to microgrooves is addressed using a new assay format, comprising orthogonal gradients of continuously varied groove pitch and depth. Dual layer etch masks are created using a combination of micropatterning and plasma polymer deposition. A silicon substrate with a constant groove width of 8 μm and with ridge width increasing from 8 μm in 0.5 μm steps across 10 mm is fabricated by photolithography. A plasma-polymerized hexane film which is 120 nm thick at one end of these grooves, and 10 nm at the other, is deposited under a diffusion mask. Reactive etching of the patterned sample transfers a gradient of groove pitch and groove depth into the silicon substrate. A silicon master with a gradient of groove depth spanning more than two orders of magnitude (less than 10 nm to over 1000 nm) is used to create an injection molding inlay for mass replication of the screening topography. Polycarbonate replicas are molded for use in cell culture studies, and the functionality of the topography as a high-throughput screening platform is investigated. The response of MDCK, h-TERT fibroblasts, and LE2 endothelial cells is examined, in terms of attachment and morphological response to the variation in topographical cues, with the aim of pinpointing the optimal combination of groove pitch and depth to elicit a tailored response from each cell type. When the range of topographical features screened on a single substrate is considered, this new assay represents a significant step forward in the parametric design and analysis of topographical cues at the biomaterial interface.

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“…This organic-inorganic multilayer TFE structure has the advantage of improving exibility as well as moisture barrier properties. Organic materials used for this purpose include polymers formed through solution processes [9][10][11][12][13][14][15] and polymers deposited using vacuum processes such as initiated CVD [16-20], thermal CVD [21], or plasma polymerization [22][23][24][25][26][27][28][29][30][31][32][33][34]. In addition, organic layers deposited by molecular layer deposition (MLD) method using a surface self-limited reaction similar to ALD can also be included in this category [35][36][37][38][39][40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

Improvement of deformation stability of Al2O3 moisture-barrier layer by insertion of 4-bipyridine organic monolayers

Lee,

Cho

2024

Preprint

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Flexible organic light-emitting diode (OLED) displays are protected from external moisture using an organic-inorganic thin film encapsulation (TFE) structure. The inorganic thin films used in TFE are excellent moisture barriers, but because they are fragile, thick organic thin films must be used together. In this study, 4,4'-bipyridine (4-BP), a small organic molecule, was inserted into the Al2O3 inorganic thin film as monomolecular layers to improve the moisture barrier and flexibility properties of the Al2O3. The 30 nm-thick Al2O3 layer without the 4-BP monomolecular layers cracked after 1,000 repeated bendings at a bending radius of 1 mm, but when these organic molecular layers were introduced, cracking occurred delayed to a radius of 0.7 mm. The effect of improving flexibility due to the introduction of these 4-BP monomolecular layers was verified through optical Ca tests before and after repeated bending and rolling. In this way, it was shown that small organic molecules such as 4-BP can be effectively used to improve the moisture barrier and flexibility properties of TFE for flexible OLED displays.

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Full‐Thickness Characterization of Plasma Polymerized Hexane Films Irradiated by an Electron Beam

Cited by 9 publications

References 27 publications

Composition and Stability of Plasma Polymer Films Exhibiting Vertical Chemical Gradients

Composition and Stability of Plasma Polymer Films Exhibiting Vertical Chemical Gradients

A Dual Gradient Assay for the Parametric Analysis of Cell–Surface Interactions

Improvement of deformation stability of Al2O3 moisture-barrier layer by insertion of 4-bipyridine organic monolayers

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