Surface Analysis of Plasma‐Deposited Polymer Films, 1

107

Plasma coating technologies have been demonstrated as being promising for the fabrication of bioactive and biocompatible materials, among others. Reported efforts are exclusively focused on the two‐step approaches, in which the bioactive component is first immobilized on a substrate, followed by a (vacuum) plasma polymerization treatment or vice versa. However, we believe that upon minimizing the plasma energy, numerous bioactive substances such as enzymes and nucleic acids can be immobilized directly in plasmas via copolymerization with organic precursors, or by direct entrapment in the organic polymer. Therefore, a dielectric barrier discharge was employed at atmospheric pressure and ambient temperature to deposit organic coatings with reasonable growth rates at power input and frequency values as low as possible. Two promising precursors, acetylene and pyrrole, were selected out of 22 organic monomers for full physicochemical characterization. While the acetylene polymer film shows resemblance with its vacuum plasma analogue, polypyrrole coatings produced in vacuum and atmospheric plasmas differ significantly.

Section: Resultsmentioning

confidence: 99%

Dielectric Barrier Discharge at Atmospheric Pressure as a Tool to Deposit Versatile Organic Coatings at Moderate Power Input

Heyse

Dams

Paulussen

et al. 2007

107

“…plasma generator (CESAR™ 136) combined with a matching unit (VM1500) made by Dressler, Stolberg, Germany, were used to establish the plasma in the reactor. Details of the experimental set‐up are given elsewhere 16. The pulse frequency can be chosen in a range between 10 and 10 4 Hz and the duty‐cycle of the pulses can be varied between 0.01 and 0.9.…”

Section: Experimental Partmentioning

confidence: 99%

“…SSIMS is a rather surface sensitive method utilizing the direct relationship between surface structure and fragmentation pattern which are observed in secondary ion mass spectra 8–12. It was shown previously that SSIMS provides information on unsaturation, branching and cross‐linking of plasma deposited polymer films 13–17. To the best of out knowledge, effects of external plasma parameters on the chemical structure of the allylamine plasma polymers have never been investigated in detail by ToF‐SSIMS before.…”

Section: Introductionmentioning

confidence: 99%

Surface Analysis of Plasma Deposited Polymer Films, 7

Oran

Swaraj

Lippitz

et al. 2006

Self Cite

Summary: Plasma deposited allylamine films were studied by “in situ” ToF‐SSIMS, XPS and NEXAFS Spectroscopy before exposure to ambient air. The influence of external plasma parameters such as duty cycle, plasma power, and monomer flow rate on (i) unsaturation, (ii) branching and cross‐linking, (iii) nitrogen surface concentration and (iv) retention of amino groups was investigated. Harder plasma conditions, which can be obtained when high duty cycles, high plasma power, and low monomer flow rates are employed, increase the unsaturated, branched and cross‐linked character of the plasma deposited films, while the surface concentration of N as well as the retention of the monomer's amino group decrease. As proven by NEXAFS findings and cross‐checked by ToF‐SSIMS results, the allylamine monomer's primary amino groups are partially transformed into other nitrogen functionalities during its plasma polymerization. Amongst them imines and nitriles are the conversion products with the highest probabilities of formation. Another conversion channel is the formation of nitrogen species not participating in the film growth. This is the reason for an increased N loss in plasma deposited allylamine films as observed independently by XPS and ToF‐SSIMS when the plasma parameters are changed from mild to hard.

“…plasma generator (CESAR™ 136) combined with a matching unit (VM1500) made by Dressler, Stolberg, Germany, was used to establish the plasma in the reactor. Details of the experimental set‐up were given elsewhere 25. The pulse frequency can be chosen in a range between 10 and 10 4 Hz and the duty‐cycle of the pulses can be varied between 0.01 and 0.9.…”

Section: Experimental Partmentioning

confidence: 99%

Surface Chemical Analysis of Plasma‐Deposited Copolymer Films Prepared from Feed Gas Mixtures of Ethylene or Styrene with Allyl Alcohol

Swaraj

Oran

Friedrich

et al. 2007

Self Cite

Plasma deposited styrene/allyl alcohol and ethylene/allyl alcohol copolymer films were prepared and characterized using XPS, NEXAFS and ToF‐SIMS. The relative partial flow rates of the co‐monomers are used as deposition process parameters to vary and all other process parameters were constrained to conditions optimized for retention of functional groups. By doing this it is possible to control certain chemical properties of the copolymer films such as unsaturation, oxygen and hydroxyl group relative surface contents. The aging behavior of the plasma copolymer films on air was studied, too. Non‐linear variations of relative oxygen contents, contents of COR species and contents of carbonyl species are obtained vs. variation of feed gas composition for both monomer combinations. The chemical character of the plasma copolymer films varies between the limits given by the respective plasma homopolymers. The observed non‐linear correlations are discussed in terms of approaches developed for classic radical copolymerization. The aging behavior of the different plasma copolymers films depends on the feed gas composition. Principally these aging phenomena known from plasma polymer aging studies of that respective monomer which dominates the character of the plasma copolymer are observed.