A new gas discharge process for preparation of non-fouling surfaces on biomaterials

A non-fouling surface containing immobilized polyethylene oxide (PEO) was achieved using an argon radio-frequency glow discharge treatment (RFGD) of polyethylene films precoated with Brij hydrocarbon-PEO surfactants. Surface wettability of RFGD-treated and washed surfaces increased the most when PEO surfactants with unsaturated and/or long alkyl tails were used. ESCA measurements of treated and washed surfaces showed increases of surface O/C ratios and ether carbon peaks in high resolution Cls spectra. These results demonstrate the retention of the PEO surfactants on the treated surfaces. Fibrinogen adsorp tion on these treated surfaces was significantly reduced, from 500 to 50 ng/cm2, indicating the non-fouling properties of the RFGD-immobilized PEO surfactants

Removal of Pendant Groups of Vinyl Polymers by Argon Plasma Treatment

Poly(acrylic acid) (PAAc) and poly(vinyl chloride) (PVC) were treated with an argon plasma to create unsaturated bonds at the surface. By use of X-ray photoelectron spectroscopy and Fourier transform infrared measurements, it was shown that the pendant groups of these polymers are removed by the argon plasma treatment. This resulted in the formation of unsaturated bonds and cross-links in the modified layer. It was found that the removal of the pendant groups is induced by UV light emitted by the argon plasma. During treatment of PAAc decarboxylation took place, which made the argon plasma more oxidative in character. The modified layer was reoxidized and eventually the PAAc surface was ablated with time. The removal of chlorine from PVC was found to be preferential, and a highly cross-linked layer, containing at least 15% unsaturated bonds, was obtained. The outermost top layer of this modified layer became oxidized after exposure to air due to a reaction between long-living radicals and oxyge

Selective Etching of Semicrystalline Polymers: CF4 Gas Plasma Treatment of Poly(ethylene)

A series of poly(ethylene) (PE) films with different degrees of crystallinity was treated with a radio-frequency tetrafluoromethane (CF4) gas plasma (48-49 W, 0.06-0.07 mbar, and continuous vs pulsed treatment). The etching behavior and surface chemical and structural changes of the PE films were studied by weight measurements, X-ray photoelectron spectroscopy (XPS), static and dynamic water contact angle measurements, scanning electron microscopy (SEM), and atomic force microscopy (AFM). With increasing crystallinity (14-59%) of PE, a significant and almost linear decrease of the etching rate was found, ranging from 50 Å/min for linear low-density poly(ethylene) (LLDPE) to 35 Å/min for high-density poly(ethylene) (HDPE). XPS analysis revealed that after CF4 plasma treatment the PE surfaces were highly fluorinated up to F/C ratios of 1.6. Moreover, CF4 plasma treatment of PE resulted in extremely hydrophobic surfaces. Advancing water contact angles up to 150 were measured for treated LDPE films. Both SEM and AFM analysis revealed that pronounced surface restructuring took place during prolonged continuous plasma treatment (15 min). The lamellar surface structure of LDPE changed into a nanoporous-like structure with uniform pores and grains on the order of tens of nanometers. This phenomenon was not observed during plasma treatment of HDPE films. Apart from surface roughening due to selective etching, pulsed plasma treatment did not result in significant surface structural changes either. Therefore, the restructuring of continuously plasma-treated surfaces was attributed to a combined effect of etching and an increase of the surface temperature, resulting in phase separation of PE-like and poly(tetrafluoroethylene)-like material, of which the latter is surface oriented

Pulsed Plasma Polymerization of Thiophene

Highly transparent (>80%) and conductive layers (10-6 S/cm) were obtained by the pulsed plasma polymerization of thiophene. The influence of power, pressure, pulse time, duty cycle, and position in the reactor on the conductivity of the resulting plasma polymerized thiophene (PPT) layers was evaluated. In the used ranges, only pressure had a significant influence on the conductivity of the deposited layer. The results could be correlated to the effect of the deposition parameters on the fragmentation of the thiophene monomer. At high pressure there was less fragmentation of thiophene, resulting in a higher conductivity of the layer. It was shown that the use of a pulsed plasma as a means to minimize fragmentation is most efficient when the off time is chosen such that the reactor is replenished with new monomer during the off period

Introduction of sulfate groups on poly(ethylene) surfaces by argon plasma immobilization of sodium alkyl sulfates

Sulfate groups were introduced at the surface of poly(ethylene) (PE) samples. This was accomplished by immobilizing a precoated layer of either sodium 10-undecene sulfate (S11(:)) or sodium dodecane sulfate (SDS) on the polymeric surface by means of an argon plasma treatment. For this purpose, S11(:) was synthesized by sulfating 10-undecene-1-ol using the pyridine-SO3 complex. The presence of sulfate groups at the polymeric surfaces was confirmed by X-ray Photoelectron Spectroscopy (XPS). The presence of an unsaturated bond in the alkyl chain of the surfactant improved the efficiency of the immobilization process. About 25% of the initial amount of sulfate groups in the precoated S11(:) layer was retained at the PE surface compared to only 6% for SDS. The maximum surface density of sulfate groups on the resulting samples was one group per 45 and 127 Å2 respectively

Mechanism of the immobilization of surfactants on polymeric surfaces by means of an argon plasma treatment: influence of the chemical structure of surfactant substrate

In this article, a study on the mechanism of the immobilization of surfactants on polymeric surfaces by means of an argon plasma treatment is described. The unsaturated surfactant sodium 10-undecenoate [C11(:)] and the saturated surfactant sodium dodecanoate (C12) were immobilized on poly(ethylene) (PE), poly(propylene) (PP), and poly(cis-butadiene) (PB) surfaces. This was accomplished by treating polymeric substrates that were coated with C11(:) or C12 with an argon plasma. Derivatization X-ray Photoelectron Spectroscopy (XPS) and Static Secondary Ion Mass Spectrometry (SSIMS) showed that during the plasma treatment surfactants were covalently coupled to the polymeric surfaces. The chemical structure of both the surfactant and the polymeric substrate influenced the immobilization efficiency. At an optimal treatment time of 5 s, about 28 and 6% of the initial amount of carboxylate groups in the precoated C11(:) and C12 layer, respectively, was retained at the PE surface. The immobilization efficiencies of C11(:) and C12 on PP were about 20 and 9%, respectively. The immobilization efficiency of C11(:) and C12 on PB were both about 7%. The results obtained in this study indicate that the immobilization proceeds via a radical mechanism

Coating of anionic surfactants onto poly(ethylene) surfaces studied with x-ray photoelectron spectroscopy

Poly(ethylene) (PE) samples were immersed in aqueous solutions of different anionic surfactants, viz. sodium dodecane sulfate (SDS), sodium 10-undecene sulfate (S11(:)), and sodium 10-undecenoate (C11(:)). When the PE samples were removed from the solutions, dried, and analyzed with X-ray photoelectron spectroscopy (XPS), surfactant was detected at the surface only if the PE samples were wetted by the surfactant solution. Wetting was accomplished by pretreating the polymer with an argon plasma for 5 s. In this way, a relatively hydrophilic surface was obtained with advancing and receding water contact angles of 89° and 31°, respectively. In a second approach, 1 vol % of hexanol was added to the surfactant solutions, thereby decreasing the surface tension of the solutions to a value below 31 mN/m, allowing direct coating of PE with the surfactants. XPS was performed to estimate the orientation of the molecules in the surfactant layer at the surface. Surfactant molecules were randomly oriented in a homogeneous layer. The thickness of this layer varied from 10 to 60 Å and increased with increasing surfactant concentration of the immersion solution