Louis J. Gerenser

Plasma Treatment of Polymers

Abstract Plasma treatment of polymers encompasses a variety of plasma technologies and polymeric materials for a wide range of applications and dates back to at least the 1960s. In this article we provide a brief review of the United States patent literature on plasma surface modification technologies and a brief review of the scientific literature on investigations of the effects of plasma treatment, the nature of the plasma environment, and the mechanisms that drive the plasma–surface interaction. We then discuss low‐radio‐frequency capacitively coupled nitrogen plasmas and their characteristics, suggesting that they provide significant plasma densities and populations of reactive species for effective plasma treatments on a variety of materials, particularly when placing the sample surface in the cathode sheath region. We further discuss surface chemical characterization of treated polymers, including some results on polyesters treated in capacitively coupled nitrogen plasmas driven at 40 kHz. Finally, we connect plasma characterization with surface chemical analysis by applying a surface sites model to nitrogen uptake of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) treated in a 40 kHz nitrogen plasma. This example serves to suggest an interesting practical approach to comparisons of plasma treatments. In addition, it suggests an approach to defining the investigations required to conclusively identify the underlying treatment mechanisms.

E.s.c.a. studies of corona-discharge-treated polyethylene surfaces by use of gas-phase derivatization

Abstract Chemically specific gas-phase reactions have been used to tag corona-discharge-induced chemical species on the surface of polyethylene. These tag reactions provide distinct moieties that can be detected via e.s.c.a. to provide a surface count of induced species. Hydroxyl, epoxy, hydroperoxy, carboxylic acid and carbonyl populations are discussed as a function of corona energy input, time after treatment and water washings.

An e.s.c.a. study of the gas-phase derivatization of poly(ethylene terephthalate) treated by dry-air and dry-nitrogen corona discharge

Abstract Gas-phase derivatization has been used along with e.s.c.a. to determine corona-discharge-induced chemical species on poly(ethylene terephthalate) (PET). Dry-air and dry-nitrogen coronas were studied. We showed that: (1) if the corona discharge treatment (CDT) power level is kept low enough, few water-soluble species are created; (2) 4% of oxygen is added to the surface with dry-air corona; (3) 75% of the oxidation products are identified as hydroperoxy, epoxy, hydroxyl, carboxylic acid and isolated carbonyl species (with hydroxyl and isolated carbonyl the prevalent species). Short-term time-dependent ageing studies show a one-to-one correspondence between the decrease in hydroperoxy species and the increase in hydroxyl and isolated carbonyl moieties. Reaction sequences are proposed to explain these data. At longer times these surface populations decrease. In general, the results from nitrogen coronas and dry-air coronas are similar.

Surface chemistry of nitrogen plasma-treated poly(ethylene-2,6-naphthalate): XPS, HREELS and static SIMS analysis

Plasma treatments typically affect only the outer few nanometers of a polymer surface and produce a complex mixture of surface functionalities. For a given plasma gas, the population of plasma-induced surface functionalities is influenced by several plasma parameters (power, pressure and residence time) and the chemical structure of the polymer. We have done a systematic investigation of the effect of these plasma parameters on the surface chemistry of a nitrogen plasma-modified polyester: poly(ethylene-2,6-naphthalate) (PEN). The surface chemistry was characterized with a combination of surface-sensitive spectroscopies; x-ray photoelectron spectroscopy (XPS), high-resolution electron energy-loss spectroscopy (HREELS) and static secondary ion mass spectrometry (static SIMS). We have found that nitrogen plasma treatment incorporates up to 13 at.% nitrogen in the upper 5 nm of PEN and disrupts both the ester groups and the naphthalene rings. Disruption of the naphthalene rings produces an aliphatic-like species and disruption of the ester groups produces either isolated carbonyl groups or, upon reaction with nitrogen, amide groups. The incorporated nitrogen is primarily in the form of amine and amide groups. Both pressure and dose were found to affect the degree of disruption of the polymer surface, the amount of incorporated nitrogen and the relative population of amine and amide groups. Copyright

The application of photoemission, molecular orbital calculations, and molecular mechanics to the silver-poly(p-phenylene sulfide) interface

The interfacial chemistry between evaporated Ag and poly(p‐phenylene sulfide) (PPS) has been investigated with x‐ray photoelectron spectroscopy (XPS). The initial stages of nucleation and growth of Ag in the subatomic‐layer regime were monitored. The PPS core level spectra exhibit no detectable changes as a function of Ag coverage; however, the Ag 3d5/2 peak position shifts ∼0.6 eV to higher binding energy at low Ag coverages. At low Ag coverages, the valence band spectra consist of two main features centered at 2.5 and 5.9 eV. Unrestricted Hartree–Fock (UHF) molecular orbital calculations suggest that the 5.9 eV band consists of weakly perturbed Ag 4d orbitals and bonding Ag 4d–S 3p hybrid orbitals. The 2.5 eV band consists of antibonding Ag 4d–S 3p hybrid orbitals. Molecular mechanics results suggest that the sulfur atom transforms from a bent to either a trigonal pyramidal or trigonal planar configuration after bonding with Ag. Both the molecular orbital calculations and molecular mechanics results sug...

X-ray photoemission studies of the lead halide valence bands

Abstract X-ray photoemission spectra of the lead halide valence bands are reported. Assignments based on a point charge model unambiguously show the Pb 6s level to occur several volts below the top of the valence band.

Chemisorption of iodine on silver clusters

Abstract Ultraviolet photoemission spectra are reported for silver clusters supported on carbon with and without an overlayer of iodine atoms. We find a broadening silver d band and change in d threshold with increasing cluster size. The difference spectra for I chemisorbed on silver clusters show two predominant peaks, whose changes with cluster size are interpreted to mean an increasing charge on I on larger clusters.

Non-Silver Amplification Processes: Part 3. Catalytic Thermal Decomposition of Te(II) Coordination Complexes via Internal Redox Reactions

AbstractA series of tellurium(II) coordination complexes of the general formulas [TeL2,X2] TeL4]X2 (L = thiourea or substituted thiourea; X = CI, Br, SCN) and [Te(S2X)2] (X = COR, CN(C2H5), P(OCH3),P(OCH3)2 P(OC2H5)2 P(C6H11)2 have been prepared and evaluated as image precursors in solution and dry amplification elements. Non-aqueous solutions of the thiourea complexes depit Te(0) at room temperature, Te(0), Pd(0) and Ag(0) being effective catalysts for the reaction. The Te(n) xanthates, Te(S2COR)2(R=CH3,C2H5, i-C3H7,n-C3H7,n-C5H11,C12H25), undergo facile catalytic thermal decomposition to Te(0), Ag(0), Pd(0) and Te(0) being effective catalysts for such processes. The mechanism of the thermal decomposition of [Te(s2CO-i-C3H7)2], has been shown by X-ray photoelectron spectroscopy to involve an intramolecular thermal ligand reduction reaction to give oxidized sulphur ligand (i.e. i-C3H7O-C(S)SSC(S)O-i-C3H7) and Te(0), ESCA experiments have also demonstrated that the amplification process is autocatalytic.

AN N-BONDED Cu(I) THIOCYANATE COMPLEX: ISOTHIOCYANATO-(1,1,1,-TRIS(DIPHENYL-PHOSPHINOMETHYL)ETHANE) COPPER(I)

Abstract The complex [Cu(((C6 H5)2 PCH2)3 CCH3) (NCS)] has been prepared and characterized by infrared, PMR, and X-ray photoelectron spectroscopy. It has been formulated as a mixture of N- and S-bonded isomers in the solid state, the ratio of the isomers depending on the conditions of isolation of the complex as well as the sampling technique used for the infrared spectral measurements (i.e., mull vs. KBr pellet). In CHCl3 solution the complex exists exclusively as the N-bonded isomer, although PMR spectroscopy indicates that a rapid exchange of the phosphorus sites of the ligand occurs at room temperature. The complex [Cu(P(C6 H5)3)2 SCN]2, in contrast, is formulated as a dimeric species in the solid state with two bridging thiocyanates. In CHCl3 solution, however, the bridges cleave to give exclusively the N-bonded monomeric three-coordinate complex.

23.4: Photoemission Investigation of Cesium-Doped tris(8-hydroxyquinoline) aluminum (Alq3) and the Effect of Dopant Diffusion

The chemical and electronic effects of Cs-doped Alq3 have been investigated using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). XPS reveals the formation of a new nitrogen species shifted to lower binding energy that increases in intensity as a function of Cs doping. UPS reveals the formation of a new gap state in the previously forbidden band gap of Alq3 after Cs doping. Both results are consistent with the formation of a Cs-Alq3 charge-transfer complex. The thermal stability of the charge-transfer complex was also evaluated using angle-resolved XPS (ARXPS). The XPS data suggests that one Cs atom attached to an Alq3 molecule is thermally stable, but the addition of a second or third Cs atom to an Alq3 molecule produces a thermally unstable complex. OLED device data also confirms the thermal instability of the Cs-Alq3 complex.