Wettability of poly(ethylene terephthalate) film treated with low‐temperature plasma and their surface analysis by ESCA

The surface of poly(ethylene terephthalate) (PET) film was modified by low‐temperature plasma with O₂, N₂, He, Ar, H₂, and CH₄ gases, respectively. After being treated by low‐temperature plasma, their surface wettability and chemical composition were investigated by means of electron spectroscopy for chemical analysis (ESCA) and contact angle measurement. The result shows that the surface wettability of PET can be improved by low‐temperature plasma, and the effect of the modification is due mainly to the kind of the gases. Mainly because of the contribution of hydrogen bonding force γ[STACK]^c_S[ENDSTACK], the surface wettability of PET treated with O₂, N₂, He, and Ar plasma for a short time (3 min) increase sharply, and the surface wettability is also improved by H₂ plasma treatment; but the CH₄ plasma treatment does not improve the wettability of PET. ESCA shows that the effect of wettability of PET is tightly related to the presence of polar functional groups that reside in the outermost surface layer of PET. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1327–1333, 1999     

Surface Modification of Fluorinated Polymers by Microwave Plasmas

We developed a new plasma treating method, incorporating the use of microwaves generated by an electronic cooking range. Using this method, polytetrafluorethylene (PTFE) and a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP) were treated. Dialkylphthalates (DAP) were used as the standard liquids of contact angle measurements for evaluation of the wetting properties of plasma treated polymers. The components of surface tension (γ_L) due to the dispersion force (γ^d _L) and the polar force (γ^P _L) of DAP were calculated by Fowkes' equation from the contact angles (θ) on polypropylene. After plasma treatment cos θ of several standard liquids on PTFE and FEP increased. The linear relationship between γ_L(1 + cos θ)/(γ^d _L)^½ and (γ^P _L/γ^P _L)^½ was verified. γ_s and γ^d _s and γ^d _s of the plasma treated PTFE and FEP also increased. From the results of ESCA analysis, it was found that a significant amount of oxygen was introduced to the polymer surface by the plasma treatment. Peel strengths of a pressure sensitive adhesive bonded to PTFE and FEP increased approximately two-to threefold if the plasma treatment was used prior to bonding.     

A Reinterpretation of Organic Liquid-Polytetrafluoroethylene Surface Interactions

The wettability of polytetrafluoroethylene (PTFE) by organic liquids is reanalyzed in terms of dispersion-polar interactions across the liquid-solid interface. The analysis provides values of γ_s ^d = 19.6 dyne/cm, and γ_S ^D = 2.0 dyne/cm for the respective dispersion and polar parts of the surface tension γ_s = 21.6 for PTFE. The definition of a polar contribution to the surface tension of PTFE clarifies detailed aspects of the wettability of this polymer by different homologous liquid series. A modified analytical definition for work of adhesion is developed and applied to this discussion.     

New fluorinated polysiloxanes containing an ester function in the spacer—II. Surface tension studies

The surface tensions of fluorinated polysiloxanes prepared by hydrosilylation of unsaturated perfluoroalkyl esters derived from undecylenic acid [CH₂?CH? (CH₂)₈? COO? CH₂? CH₂? R_F, with R_F = C₆F₁₃, C₈F₁₇, and C₈F₁₇? (CH₂)₁₀COO? CH₂? CH₂? CH?CH₂] by methylhydrodimethylsiloxane copolymers of various Si? H contents have been measured. The critical surface tensions, γ_c, and the solid surface tensions, γ^D_s, were deduced from n-alkane and water contact angle data. They decrease as the perfluoroalkyl graft content of the copolymers increases. Some of them, which are in the range of the lowest surface tension fluoro polymers known, are observed when the fluorinated segments are self-organized at the interface, i.e. when the polymers are mesomorphous or crystalline at room temperature.     

Dispersion-Polar Surface Tension Properties of Organic Solids

A new definition for work of adhesion W_a is applied to computationally define the dispersion γ_s ^d and polar γ_s ^d components of the solid surface tension γ_s = γ_s ^d + γ_s ^d for twenty-five low energy substrates. These calculated surface properties are correlated with surface composition and structure. Surface dipole orientation and electron induction effects are respectively distinguished for chlorinated and partially fluorinated hydrocarbons. Published values for critical surface tension of wetting γ_c are correlated with both γ_s ^d and γ_s.     

Plasma modification of poly(oxybenzoate-co-oxynaphthoate) film surfaces for copper metallization

Poly(oxybenzoate-co-oxynaphthoate) (POCO) film surfaces were modified by four plasma gases, Ar, O₂, N₂ and NH₃, and the effects of the plasma modification were investigated in order to understand the adhesion with copper metal. The Ar, O₂, N₂ and NH₃ plasmas converted the POCO surfaces from hydrophobic to hydrophilic. The effect of the plasma on the hydrophilic modification was in the order: Ar plasma > O₂ plasma > N₂ plasma > NH₃ plasma. The plasma modification contributed to the adhesion between the deposited copper metal and the POCO film. The NH₃ plasma was most effective in improving the adhesion, and the Ar plasma was ineffective. The plasma-modified POCO film surfaces showed quite different C_ls spectra from that of the original POCO film. There were large differences in the C_ls and N_ls spectra between the NH₃ and Ar plasma modifications. The NH₃ plasma modification did not show C_ls component #5 due to π–π^* shake-up satellite, but the Ar plasma modification did show this component. Furthermore, NH₃ plasma modification led to a new N_ls spectrum. The plasmas caused etching of the POCO film surfaces, and the etch rate depended on what plasma was used and how much RF power was used. The NH₃ plasma-modified POCO film surface showed a larger R _a (25.5 nm) than the other plasma-modified surfaces (R _a = 16.4–19.0 nm), which were comparable to that of the original surface (R _a = 14.8 nm). The NH₃ plasma led to a highly-undulated surface, and the other plasmas did not alter the surface roughness. The roughened surfaces showed contribution to enhancement of the adhesion to the deposited copper metal.     

A relationship between the fracture mechanics and surface energetics failure criteria

The reversible part of the fracture mechanics (F-M) fracture energy γ_c is redefined in terms of current theory for surface energetics (S-E) interactions at regular interfaces. These new failure criteria are applied to the definition of surface energy criteria for spontaneous interfacial failure, where γ_c = 0, produced by selected conditions of liquid-phase immersion. For cases where γ_c > 0, the total fracture energy W = γ_c + W_p, where the irreversible plastic work of surface formation W_p ≈ W ? γ_c. A qualitative relation between γ_c^1/2 ∝ W_p is observed for the case of steady-state crack propagation in peeling. For adsorption bonds, the theory provides a new method of mapping the surface energy effects of the immersion phase upon the Griffith fracture energy γ_c. Essential factors which determine water sensitivity of interfacial bonds are incorporated into the analysis and experimentally verified.     

Plasma surface modification of poly(phenylene sulfide) films for copper metallization

Poly(phenylene sulfide) (PPS) films were modified by Ar, O₂, N₂ and NH₃ plasmas in order to improve their adhesion to copper metal. All four plasmas modified the PPS film surfaces, but the NH₃ plasma modification was the most effective in improving adhesion. The NH₃ plasma modification brought about large changes in the surface topography and chemical composition of the PPS film surfaces. The peel strength for the Cu/plasma-modified PPS film systems increased linearly with increasing surface roughness, R _a or R _rms, of the PPS film. The plasma modification also led to considerable changes in the chemical composition of the PPS film surfaces. A large fraction of phenylene units and a small fraction of sulfide groups in the PPS film surfaces were oxidized during the plasma modification process. Nitrogen functional groups also were formed on the PPS film surfaces. The NH₃ plasma modification formed S—H groups on the PPS film surfaces by reduction of S—C groups in the PPS film. Not only the mechanical interlocking effect but also the interaction of the S—H groups with the copper metal may contribute to the adhesion of the Cu/PPS film systems.     

Surface and printing properties of synthetic film papers

We studied the surfaces, including both the composition effects and the processing rates, of polypropylene (PP) composite films used for synthetic paper to determine the surface free energy (γ_s) and the irregularities on the film surfaces. We correlated these two characteristics to the printing quality by assessing the facility with which the offset ink was removed from the surface of the paper and also the ink absorption. Five films with different compositions were uniaxially oriented with a flat‐die extruder at two different stretching rates. The results of scanning electron microscopy (SEM) of the films showed good dispersion and distribution of the filler particles used in the compositions of the films and also of the polystyrene (PS) dispersed throughout the PP matrix. The SEM analysis also revealed slightly high surface irregularities on the film surfaces through a high concentration of CaCO₃, which thus increased the coefficients of static and kinetic friction and the γ_s values. These film properties created better printing quality and also more strongly fixed offset ink onto the film. However, the films with high relative quantities of PS in their composition showed a high polar component in their total γ_s when compared to films with less PS or no PS in their compositions. However, because of the apolar characteristic of the offset printing ink, the ink absorption worsened. The films underwent stretching at two different rates, which did not significantly affect the γ_s values or the friction coefficients; however, they did slightly change the printing quality and ink adhesion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2346–2355, 2003     

Plasma etching treatment for surface modification of boron-doped diamond electrodes

Boron-doped diamond (BDD) thin film surfaces were modified by brief plasma treatment using various source gases such as Cl₂, CF₄, Ar and CH₄, and the electrochemical properties of the surfaces were subsequently investigated. From X-ray photoelectron spectroscopy analysis, Cl and F atoms were detected on the BDD surfaces after 3 min of Cl₂ and CF₄ plasma treatments, respectively. From the results of cyclic voltammetry and electrochemical AC impedance measurements, the electron-transfer rate for Fe(CN)₆^3−/4− and Fe^2+/3+ at the BDD electrodes was found to decrease after Cl₂ and CF₄ plasma treatments. However, the electron-transfer rate for Ru(NH₃)₆^2+/3+ showed almost no change after these treatments. This may have been related to the specific interactions of surface halogen (C-Cl and C-F) moieties with the redox species because no electrical passivation was observed after the treatments. In addition, Raman spectroscopy showed that CH₄ plasma treatment of diamond surfaces formed an insulating diamond-like carbon thin layer on the surfaces. Thus, by an appropriate choice of plasma source, short-duration plasma treatments can be an effective way to functionalize diamond surfaces in various ways while maintaining a wide potential window and a low background current.     

Surface characterization and study of Langmuir films of poly(4‐vinylpyridine) quaternized with n‐alkylbromide

The surface behaviour of poly(4‐vinylpyridine)s (P4VP) quaternized with four different alkyl chains (pentyl, hexyl, octyl and decy bromide) were studied. Surface pressure–area isotherms (π–A) at the air–water interface were determined. Depending on the length of the side‐chains, the π–A isotherms show a plateau region. An extensive plateau is observed for n > 6. The plateau pressures are similar for n = 8 and n = 10. The monolayers are stable and exhibit hysteresis phenomena. Brewster angle microscopy (BAM) is used to monitor the monolayer topography of the polymer on water subphase. To obtain information about the surface energy (SE) and the degree of hydrophobicity of these systems, we have estimated the critical surface tension, γ_c, and the dispersion force and polar contributions to SE, γ_D and γ_P, respectively, by measurements of the contact angle (CA) of water and bromobenzene on the polymer surface. The results obtained are depend on the length of the alkyl lateral chain of the functionalized polymers. © 2001 Society of Chemical Industry     

Role of polymer chain end groups in plasma modification for surface metallization of polymeric materials

How to improve adhesion between poly(oxybenzoate‐co‐oxynaphthoate) (Vecstar OC and FA films) and copper metal by Ar, O₂, N₂ and NH₃ plasma modification was investigated. The mechanism of adhesion improvement is discussed from the viewpoint of chemical and physical interactions at the interface between the Vecstar film and copper metal layer. The adhesion between Vecstar OC film and copper metal was improved by chemical rather than physical interactions. Polymer chain end groups that occur at Vecstar OC film surfaces contribute effectively to adhesion. This improvement in adhesion is due to interactions between copper metal and O?C groups formed by plasma modification. Aggregation of the O?C groups to the copper metal/Vecstar OC film interface is a key factor for good adhesion. From this aspect, heat treatment of plasma‐modified Vecstar OC films on glass plates is effective in the aggregation, and the peel strength for the copper metal/Vecstar OC film system reached 1.21 N (5 mm)^?1. Copyright © 2009 Society of Chemical Industry     

Effect of the length of branches on the critical surface tension of poly(n-alkyl methacrylates) and copolymers of stearyl methacrylate with methacrylonitrile

Critical surface tension values γ_c were measured for poly(n-alkyl methacrylates) and copolymers of stearyl methacrylate with methacrylonitrile. Surface tension values γ_L of n-alkyl methacrylate increase with increasing side chain length: γ_L = 23.2 dynes/cm for methyl methacrylate to 33.2 dynes/cm for stearyl methacrylate, but γ_c values of poly(n-alkyl methacrylate) decrease with increasing side chain length: γ_c = 36.3 dynes/cm for poly(methyl methacrylate) to 20.8 dynes/cm for poly(stearyl methacrylate). The decrease in γ_c is attributed to a tighter packing of the alkyl chain with a greater concentration of the pendent ? CH₃ group at the air/solid interface. Values of γ_c of copolymers hardly depended on the methacrylonitrile content in copolymers and did not satisfy the equation γ_c = N₁γ_c1 + N₂γ_c2 proposed by Lee. The difference in γ_c values for casting, annealing, and quenching films of poly(stearyl methacrylate) and the surface structure of copolymers were discussed using electron microscopy and measurement of melting point, heat of melting, and γ_c.     

Surface modification of PTFE by 60Co γ-ray irradiation

Surface carboxyl groups were formed during the ⁶⁰Co γ-ray irradiation of poly(tetrafluoroethylene) (PTFE) in air. Fourier transform infrared spectroscopy enables the detection of surface carboxyl groups. The contact angles were used to calculate the dispersive and polar components of the surface free energy according to a two-liquid method. The γ-ray irradiation of PTFE mainly caused degradation of the polymer. The concentration of carboxyl groups, the wettability, the friction, and the dispersive and polar components of the surface energy and the crystallinity on PTFE surface were increased, while the particle size of PTFE decreased with increasing irradiation dose. A highly modified PTFE was used to reduce the aqueous liquid repellent properties of PTFE. A 20 kGy dose for modified PTFE surface was suitable in air additivity in antifriction, anticorrosion, antifouling, lubrication, and noise reduction coatings. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 435–441, 1998     

Improved adhesion property and electromagnetic interference shielding effectiveness of electroless Cu‐plated layer on poly(ethylene terephthalate) by plasma treatment

To develop high‐quality electromagnetic interference (EMI) shielding materials, the effect of plasma pretreatment with various gases prior to Cu plating was investigated. Plasma treatment increased the surface roughness in the decreasing order of Ar > O₂ > NH₃, but adhesion of the Cu layer on poly(ethylene terephthalate) (PET) film increased in the following order of O₂ < Ar < NH₃, indicating that the appropriate surface roughness and introduction of an affinitive functional group to Pd on the surface of the PET film were key factors for improving adhesion of the Cu layer. As investigated by XPS analysis, plasma treatment with NH₃ produced N atoms on the PET film, which enhances the chemisorption of Pd²⁺ on PET film, resulting in improved adhesion and shielding effectiveness of the Cu layer deposited on the Pd‐catalyzed surface, because of the high affinity of Pd²⁺ for nitrogen. Comparatively, O₂ plasma treatment allowed the chemisorption of more Sn²⁺ than of Pd²⁺ due to a lack in the affinity of Pd²⁺ for oxygen, resulting in the lowest Pd_3d/Sn_3d ratio; thereby, the lowest EMI–shielding effectiveness (SE) value was obtained. In addition, fairly low adhesion was obtained with Ar plasma‐treated PET, even though the PET surface was significantly etched with Ar plasma, due to introduced oxygen groups on the PET surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1369–1379, 2002; DOI 10.1002/app.10272     

Synthesis, structure, and photovoltaic property of a nanocrystalline 2H perovskite-type novel sensitizer (CH3CH2NH3)PbI3

A new nanocrystalline sensitizer with the chemical formula (CH₃CH₂NH₃)PbI₃ is synthesized by reacting ethylammonium iodide with lead iodide, and its crystal structure and photovoltaic property are investigated. X-ray diffraction analysis confirms orthorhombic crystal phase with a = 8.7419(2) Å, b = 8.14745(10) Å, and c = 30.3096(6) Å, which can be described as 2 H perovskite structure. Ultraviolet photoelectron spectroscopy and UV-visible spectroscopy determine the valence band position at 5.6 eV versus vacuum and the optical bandgap of ca. 2.2 eV. A spin coating of the CH₃CH₂NH₃I and PbI₂ mixed solution on a TiO₂ film yields ca. 1.8-nm-diameter (CH₃CH₂NH₃)PbI₃ dots on the TiO₂ surface. The (CH₃CH₂NH₃)PbI₃-sensitized solar cell with iodide-based redox electrolyte demonstrates the conversion efficiency of 2.4% under AM 1.5 G one sun (100 mW/cm²) illumination.     

Homoepitaxial diamond film with an atomically flat surface over a large area

Homoepitaxial diamond films with atomically flat surface were grown using the microwave plasma chemical vapor deposition method at a low CH₄ concentration of less than 0.05% in a CH₄ and H₂ mixed gas system. In Ib (001) diamond substrates having misorientation angles of 0.5°, atomic force microscope image on the surface of film grown at 0.025% CH₄ concentration showed that the films had atomically flat surface with mean roughness of 0.04 nm in area as large as 4×4 mm² (the whole region of the substrate).     

Effect of surface polarity on self-adhesion of polymers

The work of detachment, W, of two attached polymers has been determined experimentally for systems consisting of unoxidized and chemically oxidized low density polyethylene (PE) film. The surface density of polar, mainly carbonyl, sites at the surfaces of oxidized polyethylene has been measured by adsorption of calcium ions. Independent measurements of the wettability of these surfaces by pure liquids allows the establishment of a relation between the thermodynamic free energy of adhesion, W_A, the polar contribution, γ^p_s, of the polymer to this energy and the surface density of polar sites. An attempt to correlate these parameters with the adhesion energy, W, has been made. The importance of the surface polarity on the possible mechanism of polymer self-adhesion is discussed.     

Effects of specific surface area of electrode and different electrolyte on capacitance properties in nano porous-structure CrN thin film electrode for supercapacitor

Thickness and specific surface area of the film electrode are critical parameters for supercapacitors. The relationship between the thickness and the specific surface area of the film directly affects the capacitance and electrochemical stability performance of super supercapacitors, which virtually affects the contact chance of ion in the electrolyte on the surface of electrode and the ion transport path of electrode. In this paper, the CrN thin films with a thickness of 200–3500 nm are prepared using direct current magnetron sputtering. Atomic force microscopy (AFM) technique is introduced to investigate the relationship between thickness and the specific surface area of the CrN films. The electrochemical performances of CrN electrode with the nanoporousper structure is analyzed in different electrolytes H₂SO₄, Na₂SO₄ and NaCl aquous solutions. The specific surface area of the film increases linearly with the film thickness increases. The areal capacitance is also linearly related to the specific surface area. The spurtted CrN film with a thickness of 3370 nm has a specific surface of up to 43.59 cm² per cm² footprint area. Its areal and volume capacitances reache to 53.92 mF cm^?2 and 650 F cm^?3 at 5 mV s^?1, respectively. In addition, the areal capacitance of CrN film electrode with 655 nm possesses reaches to 40.53 mF cm^?2 for 0.5 M H₂SO₄ solution, 32.69 mF cm^?2 for 0.5 M Na₂SO₄ solution and 9.17 mF cm^?2 for NaCl solution at a scan rate of 5 mV s^?1. Furthermore, the CrN film electrode exhibits excellent capacitance retention of 95.3%, 93.8% and 89.9% in H₂SO₄, Na₂SO₄ and NaCl electrolytes, respectively, after 2000 cycles. Therefore, the sputtered CrN thin film is an potential electrode material for electrochemical supercapacitors.     

Contact angle,wetting, and adhesion: a critical review

The theory of the contact angle of pure liquids on solids, and of the determination of the surface free energy of solids, γ_s, is reviewed. The basis for the three components γ^LW _s, γ⊕_s, and γ?_s is developed, and an algebraic expression for these properties in terms of measured contact angles is presented. The inadequacy of the 'two-liquid' methodology (which yields a parameter, 'γ^p') is demonstrated. Attention is given to contact angle hysteresis and to the film pressure, π_e. Some recommendations are made with regard to contact angle measurements. A new treatment of hydrophilicity, and of the scale of hydrophobic/hydrophilic behavior, is proposed. It is shown that there are two kinds of hydrophilic behavior, one due to Lewis basicity (electron-donating or proton-accepting structures) and the other due to Lewis acidity (electron-accepting or proton-donating structures). The properties γ^? and γ^⊕ are the quantitative measures of these types of behavior and they are structurally independent of each other. A triangular diagram, with γ^LW at the hydrophobic corner, and γ^⊕ and γ^? at the two hydrophillic corners, is suggested.