ESCA applied to polymers. XXI. Investigation of sample-charging phenomena

Sample-charging phenomena arising in the ESCA experiment have been investigated for a series of polymers. For samples studied as films or powders mounted insulated from the spectrometer probe and for gold under similar conditions it is shown that over a wide range of operating conditions, equilibrium charging shifts are characteristic of the sample and show a strong dependence on the theoretically calculated total photoionization cross sections. The surface sensitivity of the phenomenon has been demonstrated by monitoring changes in charging shifts as a function of hydrocarbon contamination. For polymer films mounted directly in contact with the spectrometer, the charging shifts exhibit time-dependent behavior. The utility of studying sample-charging shifts as an interesting phenomenon in its own right is demonstrated by reference to changes which occur consequent upon surface modification of an ethylene–tetrafluoroethylene copolymer system in RF plasmas excited in inert gases.     

An EQCM investigation of charging RuO2 thin films prepared by the polymeric precursor method

An electrochemical quartz crystal microbalance (EQCM) study of RuO₂ thin films, prepared by the sol-gel precursor method, is presented. The X-ray diffraction (XRD) analysis demonstrates that RuO₂ films were crystallized in the rutile phase and scanning electron microscopy investigations indicated the formation of a smooth surface. Cyclic voltammetry and EQCM studies were performed simultaneously in order to investigate the charging processes of the RuO₂ films in 0.1 M HClO₄. The voltammetric and mass versus potential responses present three well-defined regions associated with the RuO₂ redox couples. Based on these results and on the mass-charge relationships, the corresponding charging mechanisms are proposed. In the potential region governed by the Ru³⁺/Ru⁴⁺ redox couple, the mass-charge relation can be associated with the double-injection of protons and electrons. The other regions correspond to water release and oxyhydroxide species formation during charging.     

ESCA studies of polymers. XIII. Shake-up phenomena in substituted polystyrenes

Shake-up phenomena in a series of para-substituted polystyrenes have been studied by ESCA. Comparison with other spectroscopic data and with theoretical calculations within the sudden approximation, equivalent cores model, and CNDO SCF MO formalism identifies the shake-up structures as arising predominantly from π^*← π transitions involving the highest occupied and lowest unoccupied orbitals of the pendant phenyl groups.     

ESCA applied to polymers. XV. RF Glow-discharge modification of polymers,studied by means of ESCA in terms of a direct and radiative energy-transfer model

The crosslinking of an ethylene–;tetrafluoroethylene copolymer by exposure to an argon plasma, excited by an inductively coupled RF field, is studied over a wide range of pressures and power loadings. The results are interpreted in terms of a two-component, direct and radiative energy-transfer model showing that the outermost monolayer crosslinks rapidly via direct energy transfer from argon ions and metastables.     

ESCA applied to polymers. XXXI. A theoretical investigation of molecular core binding and relaxation energies in a series of prototype systems for nitrogen and oxygen functionalities in polymers

Nonempirical LCAO MO SCF computations (in the ΔSCF formalism) were performed on the ground and core-hole states of a range of nitrogen-containing model systems which encompass most of the common functionalities of interest in the study of polymers. The data complement those previously presented on oxygen functionalities and show that for specific functionalities (e.g. nitrate esters and nitriles) substituent effects can be substantially different than normally anticipated on the basis of a simple additivity model. A comparison was drawn in appropriate cases with experimental data on simple model systems and polymers.     

ESCA studies of polymers. VII. Shake-up phenomena in some alkane–styrene copolymers

Shake-up satellites corresponding to π^* → π transitions accompanying C_1s core ionizations have been studied for polystyrene and a series of alkane–styrene copolymers. It is shown that the shake-up intensities are additive in nature and give a direct measure of copolymer compositions.     

ESCA applied to polymers. XVIII. RF glow discharge modification of polymers in helium,neon, argon,and krypton

The crosslinking of an ethylene–tetrafluoroethylene copolymer by exposure to a variety of inert gas plasmas, excited by an inductively coupled radiofrequency (RF) field, has been studied. The rates for direct and radiative energy-transfer processes are determined within the framework of a kinetic model of the system and are shown to have a strong dependence on the sustaining gas, as do the average depths of penetration of the ions and metastable species. Helium is found to be the most efficient gas for the crosslinking of the outermost few monolayers whereas the crosslinking of the subsurface and bulk polymer is best effected by neon. Madelung charge potential calculations have been performed to simulate the experimentally determined x-ray photoelectron spectroscopy (ESCA) spectra to elucidate several features of the mechanisms involved.     

ESCA applied to polymers. XXVI. Investigation of a series of aliphatic,aromatic, and fluorine-containing polycarbonates

The absolute and relative binding energies for the C_1s, O_1s, and F_1s core levels have been determined using x-ray photoelectron spectroscopy (ESCA) for a series of aliphatic, aromatic, and fluorine-containing polycarbonates. Comparisons of these experimentally determined, core-level binding energies with theoretical calculations using the ground-state potential model in the CNDO/2 SCF MO formalism as well as model compounds have been made on the C_1s and O_1s core levels. The degree of polymerization for low-molecular-weight fluorine-containing polycarbonates, as determined from ESCA measurements, is compared to measurements by vapor-phase osmometry and ¹⁹F-NMR.     

Application of ESCA to polymer chemistry. XVI. Electron mean free paths as a function of kinetic energy in polymeric films determined by means of ESCA

Electron mean free paths as a function of kinetic energy have been measured by the substrate overlayer technique for in situ-polymerized films of poly(p-xylylene) and the monochloro- and monobromo-substituted derivatives. The results are compared with previous estimates of mean free paths available in the literature for organic materials. Comparison is also drawn with corresponding experimental data for typical metals and semiconductors, and it is shown that organic polymers fit into a consistent picture which may be rationalized on the basis of existing theory. For electrons of kinetic energy ～969 eV, ～1170 eV, 1202 eV, and 1403 eV, mean free paths of ～14 Å, ～22 Å, ～23 Å, and ～29 Å, respectively, are obtained for the poly(p-xylylene) polymer films studied in this work.     

Plasma polymerization. II. An ESCA investigation of polymers synthesized by excitation of inductively coupled RF plasma in perfluorobenzene and perfluorocyclohexane

The plasma polymers formed in glow and nonglow regions of an inductively coupled RF plasma with perfluorobenzene and perfluorocyclohexane are discussed as a function of operating conditions of the plasma by means of ESCA. The core levels of the plasma polymers are shown to be strikingly different but characteristic of a well-defined but complex polymerization scheme. For the nonglow regions fluorine incorporation is shown to be greater than for polymers prepared in the glow regions and a preponderance of CF₂ features is apparent. Perfluorobenzene deposits polymer faster than perfluorocyclohexane and changes in component composition of the C_1s profile are studied as a function of operating conditions of the gas plasma.     

Effect of chloride anion on the electrochemical charging of gold nanoparticle films

Reactivity of halide anion (Cl^?) with monolayer-protected gold nanoclusters (MPCs) of 1.8 nm in diameter has been studied. Typically, thin films of MPCs were prepared on an electrode surface and immersed in aqueous solutions containing Cl^?. It was observed that Cl^? inevitably resulted in the destruction of electrochemical charging of MPC films, which was studied and analyzed in details by cyclic voltammetry, electrochemical quartz crystal microbalance, and X-ray photoelectron spectroscopy measurements. The destruction is most likely due to the strong affinity of Cl^? for the surface of MPCs, leading to a significant variation of the surface structure and thereby quenching the electrochemical charging property.     

Plasma polymerization: An ESCA investigation of polymers synthesized by excitation of inductively coupled RF plasmas in isomeric difluoroethylenes

The polymers produced by glow discharge from three isomeric monomers are examined by ESCA. The polymer produced from 1,1-difluoroethylene is discussed in some detail and compared with those prepared from the two 1,2-difluoroethylene isomers. Charge distributions for the neutral molecules and their radical cations are calculated within the INDO SCF MO formalism and a possible reaction scheme that involves fluoroacetylene is outlined.     

Studies on transport phenomena in electrothermal vaporization sample introduction applied to inductively coupled plasma for optical emission and mass spectrometry

In the present work electrothermal vaporization (ETV) was used in both inductively coupled plasma mass spectrometry (ICP-MS) and optical emission spectrometry (OES) for sample introduction of solution samples. The effect of (Pd + Mg)-nitrate modifier and CaCl₂ matrix/modifier of variable amounts were studied on ETV-ICP-MS signals of Cr, Cu, Fe, Mn and Pb and on ETV-ICP-OES signals of Ag, Cd, Co, Cu, Fe, Ga, Mn and Zn. With the use of matrix-free standard solutions the analytical curves were bent to the signal axes (as expected from earlier studies), which was observed in the 20–800 pg mass range by ICP-MS and in the 1–50 ng mass range by ICP-OES detection. The degree of curvature was, however, different with the use of single element and multi-element standards. When applying the noted chemical modifiers (aerosol carriers) in microgram amounts, linear analytical curves were found in the nearly two orders of magnitude mass ranges. Changes of the CaCl₂ matrix concentration (loaded amount of 2–10 μg Ca) resulted in less than 5% changes in MS signals of 5 elements (each below 1 ng) and OES signals of 22 analytes (each below 15 ng). Exceptions were Pb (ICP-MS) and Cd (ICP-OES), where the sensitivity increase by Pd + Mg modifier was much larger compared to other elements studied. The general conclusions suggest that quantitative analysis with the use of ETV sample introduction requires matrix matching or matrix replacement by appropriate chemical modifier to the specific concentration ranges of analytes. This is a similar requirement to that claimed also by the most commonly used pneumatic nebulization of solutions, if samples with high matrix concentration are concerned.     

Plasma polymerization. VI. An ESCA investigation of the RF plasma polymerization of perfluoro-2-butyl tetrahydrofuran

Perfluoro-2-butyl tetrahydrofuran was polymerized by an RF glow discharge technique and detailed ESCA studies were made of the resultant films. The rate of film deposition was sensitively dependent on the W/FM parameter and the site of deposition. The ESCA data show that the molecular rearrangement accompanying plasma polymerization and the oxygen functionality is at a significantly lower level than the starting material. Under appropriate conditions plasma polymerization produces material with a C:F stoichiometry of 1:2, although the ESCA data show that the polymer is drastically different from PTFE. ESCA studies are also reported on thin films of the monomer studied at low temperature.     

Plasma polymerization. III. An ESCA investigation of polymers synthesized by excitation of inductively coupled RF plasmas in perfluorocyclohexa-1,3- and 1,4-dienes,and in perfluorocyclohexene

The plasma polymers prepared from perfluorocyclohexa-1,3-diene, perfluorocyclohexa-1,4-diene, and perfluorocyclohexene have been investigated by ESCA. The carbon-to-fluorine stoichiometries of the diene-derived polymers are similar and close to that of the starting material. The polymer prepared from perfluorocyclohexene is depleted in fluorine compared to the fluorine content of the “monomer.” The polymers prepared in nonglow regions are also studied and shown to be high in C F₂ derived species. The results are compared with those for perfluorobenzene and perfluorocyclohexane, and the polymerization rates are in the order C₆F₆ > C₆F₈ 1,3 ～ 1,4 > C₆F₁₀ ～ C₆F₁₂. The variations in composition of the plasma polymer as revealed by ESCA as a function of the polymerization conditions are discussed.     

锂在共轭双键高分子中的电化学嵌入反应I.锂在聚吡咯中嵌入过程的电子能谱研究

通过电子能谱(AES 和ESCA)研究了锂-聚吡咯电池的放电反应,认为该电池的放电是锂在聚吡咯的嵌入过程,嵌入的锂主要是以Li[+]存在,其1s电子的结合能为56.0eV.Li[+]在嵌合物中的扩散系数D为10[-12]一10[-13]cm[2].s[-1]数量级。