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Surface restructuring in ambient air of medical grade silicone rubber surfaces modified by repeated RF plasma treatments using various discharge gases including oxygen, argon, carbon dioxide and ammonia, was studied quantitatively. From advancing and receding water contact angle data, the fraction of the surface covered by mobile and immobile polar groups, and a characteristic time constant of the restructuring process were calculated. For argon plasma treated surfaces, the fraction of immobile polar groups increased with repeated plasma treatments, but remained relatively constant for samples repeatedly treated by an ammonia plasma. The use of an oxygen plasma only yielded incorporation of mobile polar groups but not of immobile polar groups. The increase in the restructuring time constants of argon and ammonia plasma treated silicone rubber with the number of plasma treatments suggested enhanced crosslinking of the silicone rubber by these plasmas. In contrast, when an oxygen plasma was repeatedly used, the restructuring time constant decreased suggesting chain cleavage by an oxygen plasma. Tentatively, the carbon dioxide plasma treatment of silicone rubber may initially (up to 3–4 repeated treatments) yield chain cleavage, while the occurrence of crosslinking is indicated after more repetitions.

Commercial polyvinylchloride (PVC) sheets were treated by plasma immersion ion implantation, PIII. Samples were immersed in argon glow discharges and biased with 25 kV negative pulses. Exposure time to the bombardment plasma changed from 900 to 10,800 s. Through contact angle measurements, the effect of the exposure time on the PVC wettability was investigated. Independent of t, all samples presented contact angles, θ, equal to zero after the treatment. However, in some cases, surface hydrophilization was not stable, as revealed by the temporal evolution of θ. Samples bombarded for shorter periods recovered partially or totally the hydrophobic character while the one exposed for the longest time stayed highly hydrophilic. These modifications are ascribed to the Cl loss and O incorporation as shown by XPS measurements. Furthermore, the mobility of surface polar groups and the variation in the cross-linking degree can also affect the PVC wettability.

Pure cellulose samples were Ar- and O2-RF-plasma treated under various external plasma parameter conditions. Plasma induced macromolecular chain and pyranosidic ring cleavage mechanisms are discussed based on survey and high resolution ESCA and ATR-FTIR analysis of cellulose, discharge-exposed cellulose, and discharge-exposed and TFAA and PFPH-derivatized cellulose samples. Analyses have also been made of bothin situ andex situ post plasma oxidation reactions. The new plasma created functionalities were identified and their relative ratios were related to plasma parameters. It was found that Ar plasma treatments initiate reactions mainly associated with the cleavage of C1–C2 linkages leading to the formation of C=O and O-CO-O groups, while O2-plasma treatments are associated with more intense pyranosidic ring (C-O-C bonds) splitting mechanisms. As a result of our detailed investigation of the high resolution C1s spectra of cellulose and carbohydrates we have reassigned the nonequivalent carbon bond affiliation (C-OH, C-O-C, and C-C) at 285–287 eV.

Concentration of neutral oxygen atoms in the flowing post-discharge of a pure oxygen microwave discharge at different experimental conditions was determined with a nickel catalytic probe. The post-discharge reactor was setup for metal surface cleaning. It worked at the pressure between 20 and 100 Pa and at output power of the microwave plasma generator between 80 and 150 W. At those experimental conditions the O-atom density was found to be of the order of 1021 m−3. It increased both with increasing pressure and microwave power. The degree of dissociation of oxygen molecules, on the other hand, decreased with increasing pressure.

We have used Time of Flight Secondary Ion Mass Spectroscopy (TOF-SIMS) in combination with X-ray photoelectron spectroscopy (XPS) to study chemical changes taking place at the surface of pure cellulose paper samples treated in N2 plasma for periods of time up to 60 seconds. High resolution TOF-SIMS spectra permit the detection of various functionalities containing nitrogen, even following very brief (∼2s) plasma exposure. Correlations between chemistry and surface properties, such as water wettability, are presented and discussed.

Polymerization of acrylic acid with hexamethyldisilazane (HMSZ) was carried out in a mixture by use of pulsed and continuous wave plasmas. The polymer deposition rate and the chemical structures of product films were investigated with regard to the power effects of the plasmas. A copolymer-like structure was formed in general, but the products were not necessarily composed of the simple agglomeration of the polymer components. The power consumed in plasma polymerization influenced the chemical structure, and oxide, in the form of Si—O, was produced more densely in the polymers at higher rather than lower powers. The polymer structure was related to the chemical properties, and the surface wetting was also changed by the power used in the plasma copolymerization. The films were moderately hydrophilic in the polymers produced at lower wattages, but became as hydrophobic as those from HMSZ when prepared at high wattages.

The emission of UV light as well as chemical reaction in plasmas allow them to be used for decontamination of food packaging. Sterilization efficiency of different dielectric barrier discharge (DBD) setups at atmospheric pressure was investigated for spores of B. subtilis and A. niger sprayed onto PET foils. In normal DBDs the efficiency of spore reduction in different gases (nitrogen, argon, synthetic air) can be related to the UV spectra of these gases in the discharge. With special so-called cascaded dielectric barrier discharges (CDBDs) a fast reduction of viable cells by more than four orders of magnitude is possible within few seconds, even for UV resistant cells. The sealing properties of commonly used PE-PET-laminate can be maintained in CDBD which is not observed for single-gap DBD.

Gas-phase chemistry of tetramethyl-1,3-cyclobutanedione (TMCB) and formaldehyde plasmas have been studied within situ Fourier Transform Infrared (FTIR) Spectroscopy. Our previous work indicated that methyl methacrylate (MMA) dissociates to intermediate species of dimethylketene (DMK) and formaldehyde in MMA plasmas. This investigation of DMK dimer (TMCB) and formaldehyde plasmas is a continuation of our effort to understand the plasma polymerization chemistry of MMA. FTIR spectra confirmed the presence of DMK in TMCB plasmas and a polymeric thin film was deposited. Formaldehyde plasmas did not deposit any film for our experimental condition. Furthermore, plasma polymerized TMCB (PPTMCB) films exhibit UV photoluminescence similar to that of PPMMA films. Therefore, DMK is proposed to be the gas-phase precursor of photoluminescence chromophores in both PPMMA and PPTMCB films.