Hydrophobic polymer films plasma-polymerized from CF4/hydrocarbon and hexafluroacetone/hydrocarbon mixtures

Polymer films were deposited from the plasma polymerization of the mixtures of hydrocarbons, ethane, ethylene, and acetylene, and tetrafluoromethane (CF₄) or hexafluoroacetone (HFA). The surface properties, the advancing contact angle of water, and surface energy of the films deposited and the chemical composition at the outermost layer of the films are discussed from the data of the angular XPS measurements. The plasma polymers deposited from the CF₄/hydrocarbon and HFA/hydrocarbon mixtures contained fluorine atoms whose content depended on the CF₄ or HFA concentration of the mixtures. The hydrophobicity of the films deposited could not be determined by the fluorine content of the films but by the chemical composition of the fluorine moieties at the outermost layer of the films. The CF₃ moieties rather than the CF₂ and CF moieties contribute largely to the hydrophobicity of the films. The plasma polymer films deposited from the HFA/acetylene (87.5 mol % HFA) showed higher hydrophobicity (the surface energy is 9.7 mJ/m²) than those from the CF₄/acetylene mixture (87.5 mol % CF₄) (the surface energy is 13 mJ/m²).     

Preparation of thin films containing sulfonic acid and carboxylic acid groups by plasma polymerization of perfluorobenzene/sulfur dioxide and perfluorobenzene/carbon dioxide mixtures

Summary Plasma polymerizations of the mixture of perfluorobenzene (PFB) and sulfur dioxide (SO₂) or carbon dioxide (CO₂), and the mixture of benzene (BZ) and SO₂ or CO₂ were investigated to obtain plasma polymer films with ionic groups such as sulfonic or carboxylic acid groups. The plasma polymerization of the mixture of PFB or BZ and SO₂ gave plasma polymer films containing sulfonic acid groups. The plasma polymerization of the mixture of PFB and CO₂ deposited plasma polymer films with carboxylic acid groups but that of the BZ/CO₂ mixture deposited plasma films with no carboxylic acid groups.     

Sulfonic acid group-containing thin films prepared by plasma polymerization

Plasam polymerization of hydrocarbon/sulfure dioxide mixtures, C₂H/SO₂, C₂H₄/SO₂, and CH₄/SO₂ mixtures, was investigated to obtain thin films containing sulfonic acid groups. Plasma polymerization of C₂H₂/SO₂ and C₂H₂/SO₂ mixtures gave filmlike products but that of the CH₄/SO₂ mixtures did not. The plasma polymers possessed much amount of sulfur and oxygen moieties with hydrocarbon chains. The sulfur moieties involved thio, sulfite, and sulfonic acid groups. This groups was a main product and reached 70–80 mol % of the total sulfur moieties. The remains (20–30 mol %) were sulfonic acid and sulfite groups. The oxygen moieties were hydroxyl and carbonyl groups with small amount of carbonxyl groups. The plasma polymers showed and hydrophilicity (the surface energy was 54–56mN/m) and good antithrombogenity.     

Plasma polymerization of tetrafluoroethylene

The plasma polymerization of C₂F₄ was carried out in both continuous wave and pulsed rf discharges to establish the effects of reaction conditions on the kinetics of polymer deposition and the polymer structure. ESCA spectra of the polymer show evidence for ? CF₃, ? CF₂, and ? CH₂? groups. Under conditions favoring low deposition rates, the dominant functional group is ? CF₂? . At higher deposition rates the concentration of ? CF₂? groups is reduced and a more crosslinked polymer is produced. Both polymer deposition rates and polymer structures were essentially identical when using continuous wave and pulsed rf discharges.     

Pulsed plasma deposition from 1,1,2,2‐tetrafluoroethane by electron cyclotron resonance and conventional plasma enhanced chemical vapor deposition

Pulsed electron cyclotron resonance (ECR) plasmas from 1,1,2,2‐C₂H₂F₄ are used to deposit fluorocarbon films. The deposited films have a F : C ratio of 1, with only slight variations in % CF_x as the deposition pressure is decreased. The optical emission (OES) spectra of the pulsed C₂H₂F₄ plasmas show high intensity peaks for H, C₂, and C₃, with lower intensity CF₂ and F peaks. The dominant OES peak shifts from H_α to C₂ when the pressure is reduced, most likely a result of the increased electron temperature at the lower pressure. Gas‐phase recombination reactions may be occurring between the OES sampling region and the deposition substrate (～ 8‐in. distance), producing fluorocarbon molecular deposition species, thus accounting for the high degree of fluorination in the deposited films. Parallel plate plasma deposited films from C₂H₂F₄ show less fluorination than their ECR counterparts, as well as vastly different OES spectra, with CF₂ peaks dominating the spectra versus H and C₂. The presence of ion bombardment in the parallel plate system tends to defluorinate the depositing films, and thus can account for the less fluorinated films deposited in the parallel plate versus ECR systems. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2084–2092, 2001     

XPS and IR analysis of thin barrier films polymerized from C2H4/CHF3 ECR-plasmas

Thin fluorocarbon polymer films are prepared on PE-foils in low-pressure electron cyclotron resonance plasmas using ethylene (C₂H₄) and trifluoromethane (CHF₃) as monomers. The thin fluorinated hydrocarbon layers strongly reduces the permeability of polyethylene to alkanes. For example, the permeation of toluene was decreased by a factor of about 100 by a single, thin fluorocarbon layer. A further reduction of the permeation down to a factor of 1600 can be obtained by a multilayer coating. X-ray photoelectron spectroscopy and Fourier transform IR spectroscopy are used to characterize the plasma polymerized films. It is shown that the addition of CHF₃ to a C₂H₄ plasma leads to an increase of CF₃—, CF₂—, and CF— groups and to a decrease of CH₃— and CH₂— groups in the film. The chemical composition of the polymer layers and their toluene permeabilities are discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 717–722, 1997     

Surface modifications of polymers with fluorine-containing plasmas: Deposition versus replacement reactions

Surfaces of polyethylene; poly(vinyl fluoride), poly(vinylidene fluoride), poly(tetrafluoroethylene), cellulose acetate butyrate, and polyoxymethylene were modified in various cold plasma reactions; feed gases to the plasma reactor were trifluoromethane, hexafluoroethane, and tetrafluoromethane. Using X-ray photoelectron spectroscopy (ESCA) to characterize the surfaces, it was established that the plasma reactions lead to fluorinated surfaces containing ? CF₃, ? CF₂, and ? CF groups, All of these fluorinated surfaces exhibit advancing contact angles (with water) larger than 900. However, differences in the ESCA spectra, weight-gain/-loss measurements and scanning-electron-microscopy (SEM) photographs reveal that the mechanisms of fluorination in the various plasma environments are markedly different. The CF₃H gas polymerizes in the gas phase of the plasma and deposits a smooth, fluorinated film on polymers and other substrates. The C₂F₆ plasma simultaneously etches polymers and polymerizes onto polymer surfaces. The CF₄ plasma etches and reacts with the polymer surface but does not polymerize. For polyoxymethylene, the combined roughening (by etching) and fluorination of the surfaces lead to completely non-wettable surfaces (water contact angle approximately 180°). The highly non-wettable surfaces of these two polymers are believed to result from the physical etching and roughening at a very fine scale (approximately five micrometers) while the outermost surfaces are reacting to become highly fluorinated.     

Synthesis and Properties of Fully Triphenylamine-based Polyamides Bearing 3,5-bis(Trifluoromethyl) and/or 3,5-dimethyl Substituents on the Pendent Phenyl Units

Four new fully triphenylamine-based polyamides coded as polyamide (CF₃,CF₃), polyamide (CF₃,CH₃), polyamide (CH₃,CF₃), and polyamide (CH₃,CH₃) were synthesized by the phosphorylation polyamidation reaction from various combinations of 3,5-bis(trifluoromethyl)-4′,4″-dicarboxytriphenylamine, 3,5-dimethyl-4′,4″-dicarboxytriphenylamine, 3,5-bis(trifluoromethyl)-4′,4″-diaminotriphenylamine, and 3,5-dimethyl-4′,4″-diaminotriphenylamine. All the polyamides were amorphous and readily soluble in many common organic solvents and could be solution-cast into transparent, flexible, and strong films with good mechanical properties. They had useful levels of thermal stability associated with high glass-transition temperatures of 268–287°C and 10?wt%-loss temperatures in excess of 500°C. Cyclic voltammograms of the film of polyamide (CH₃,CH₃) on the indium-tin oxide-coated glass substrates exhibited two oxidation redox couples with E_1/2 around 0.82 and 1.29?V vs. Ag/AgCl in tetrabutylammonium perchlorate/acetonitrile solution, accompanied by a color change from pale yellow neutral state to dark green oxidized state. The CF₃-substituted polyamides displayed a higher oxidation potential and less electrochemical stability as compared to the CH₃-substituted analogues.     

Hexafluoropropylene plasmas: Polymerization rate–reaction parameter relationships

Plasma polymerization generates thin, pinhole-free, and highly adhering films and is often described by the ratio of power to mass flow rate (energy per mass). This research explores the relationships between plasma reactor parameters such as monomer flow rate, plasma power, and reactor pressure and the rates of polymerization, etching, and deposition. The chemical structure of the amorphous, crosslinked plasma polymerized hexafluoropropylene consists largely of similar amounts of C*-CF, CF, CF₂, and CF₃ groups and some C-C groups. A dimensionless plasma parameter (E) proportional to power and inversely proportional to flow rate cubed was derived. E, reflecting both plasma energy and residence time, was used to describe various aspects of the plasma reactions. A dimensionless exponential expression successfully described the dependence of pressure on E with a master curve. An expression for polymerization efficiency (polymer conversion) derived in part through a mass balance was also successfully related to E using an exponential master curve. The rate of deposition was described as the difference between the rates of polymerization and etching. The deposition efficiency maximum and plateau were successfully described by the difference between polymerization and etching efficiencies, each related exponentially to E. The technique used to derive parameters to describe the dependence of plasma reactions on plasma operating conditions can be applied to any monomer/reactor system.     

Plasma polymerization of hexafluoropropylene: Film deposition and structure

Thin, pinhole-free, highly adhering films for advanced technology applications can be deposited through plasma polymerization, a low temperature, solvent-free process. This research studies the influence of plasma environment (power, pressure, and monomer mass flow rate (F_m)) on the plasma polymerization of hexafluoropropylene (HFP) using a common industrial parallel-plate plasma reactor. The deposition and structure of the transparent, yellow, and highly adhering plasma polymerized HFP (PPHFP) film are investigated. The rate of polymerization (R_p) increases with power (W) and reaches a plateau when the plasma changes from energy starved to monomer starved while the rate of etching (R_e) continues to increase. The rate of deposition (R_d), the difference between R_p and R_e, increases with W, reaches a maximum, and then decreases. In a monomer starved plasma R_d increases with F_m or pressure through a more efficient utilization of the energy supplied at a given W or even at a given W/F_m. The abstraction of F and the preferential scission of the C? CF₃ bond can explain the F/C ratio of 1.5, the significant amount of double bonds, and the relative lack of CF₃ in a PPHFP that consists of CF₃, CF₂, and CF groups. A gas phase dominated polymerization produces submicrometer particles some of which agglomerate into spheres. Both the particles and the spheres deposit on the surface and are incorporated into the film with further polymerization. © 1995 John Wiley & Sons, Inc.     

Functionalization of HDPE powder by CF4 plasma surface treatment in a fluidized bed reactor

The surface of HDPE polymer powder was fluorinated by CF₄ plasma in a fluidized bed reactor. Plasma is generated by an inductively coupled electrode at 13.56 MHz (rf) frequency, connected to an auto matching network and an rf power generator. In plasma surface fluorination, the CF₄ gas is diluted with He gas. The experimental variables are treatment time and rf power. The chemical property of the modified powder has been determined by using ESCA and FTIR. Plasma surface fluorination with the powder in a fluidized bed reactor results from the formation of CHF-CF₂, CHF-CHF and CF₂ groups. These fluorine functionalities and the fluorine atomic ratio on the surface increase with the treatment time and rf power. It has been found that the composite parameter is a good measure for determining the effect of total energy input on the plasma surface treatment of polymer powder in a fluidized bed reactor.     

Plasma polymerization of fluorobenzenes/SO2 mixtures

Summary Plasma polymerization of mixtures of fluorobenzenes (perfluorobenzene (PFB), pentafluorobenzene (PnFB), and tetrafluorobenzene (TFB)) and sulfur dioxide (SO₂) is carried out for preparation of plasma polymers containing both fluorine and sulfur moieties. The chemical composition of the polymers is inspected by FT/IR and XPS, and the ion-exchange capacity and the electrical conductivity are measured. Plasma polymers prepared from these mixtures are fluro polymers with either of sulfonic acid or sulfinic acid groups. The ion-exchange capacity is 0.49 (for polymers from the PFB/SO₂ mixture), 0.94 (for those from the PnFB/SO₂ mixture), and 1.31 meq/g-polyer (for those from the TFB/SO₂ mixture). The electrical conductivity at a relative humidity of 70 %RH is 8.3 × 10^–9, 3.6 × 10^–7, and 4.3 × 10^–5 S/cm, respectively.     

New fluorine-containing polyorganosilsesquioxanes: Preparation and properties

It has been found that hydrolysis of three-functional alkoxysilanes, such as R^FOCH₂Si(OR^F)₃, R^F = CH₂CF₃, CH₂CF₂CF₃, CH₂CF₂CF₂CF₃, and CH₂CF₂CF₂CF₂CF₃, under mild conditions upon exposure to air moisture in the presence of ??-aminopropyltriethoxysilane results in the formation of hydrophobic coatings from fluorine-containing polyorganosilsesquioxanes directly on the substrate. Polymers have a layered ladder structure. The hydrophobicity and low values of refractive indices, surface energy, and its polar component, as well as the simplicity of the preparation, determine the possibility of using polyorganosilsesquioxane films as antireflection protective coatings for laser optics.     

Ta and TaN adhesion to high-temperature fluorinated polyimides. Surface and interface chemistry

The practical adhesion of Cu/Ta to high-temperature fluorinated polyimides (FPIs) was initially good but failed after the reliability test involving treatment under the FPI curing condition five times (T₅). But a thin layer (40 nm) of TaN greatly improved the reliability of the Cu/Ta-to-FPI adhesion. Both CF₄ and in situ Ar plasma treatments of FPIs prior to metal deposition enhanced the metal-to-FPI adhesion strength. CF₄ plasma enriches the FPI surface with fluorine atoms and most of fluorine is bound to carbon as CF₃, CF₂, and CF. Ar plasma first destroys CF₃ and then C=O groups of the FPIs to yield a polar surface. The locus of failure by a 90° peel test was found to be within the Ar-plasma-modified FPI layer but it moved toward the bulk of FPI, i.e. away from the metal-polymer interface, after the T₅ reliability test. The locus of failure in the case of weak adhesion where no plasma treatment was done on FPI films was in the near-interface region within the FPI layer, and the failure seemed to occur in the weak boundary layers of FPI surfaces. Plasma treatment removes weak boundary layers and also increases FPI surface roughness. These two effects combined improved the metal-to-FPI practical adhesion.     

Surface modification of UHSPE fibers through allylamine plasma deposition. I. Infrared and ESCA study of allylamine plasma formed polymers

Allylamine (CH₂?CH? CH₂? NH₂) was polymerized through rf generated plasma at varying powers and times. Chemical groups and elemental compositions in the polymers were studied using ESCA and infrared spectroscopy. It was observed that plasma derived polymers contained a significant number of primary amines, along with some secondary and tertiary amines, imines, and nitrile groups. Plasma derived polymers had a complex structure and contained unsaturated groups. A considerable amount of oxygen, primarily from residual air in the plasma reaction chamber, and possibly from atmosphere when plasma polymers were exposed to air, was responsible for carbonyl, amide, ether, and hydroxyl groups found in the polymer structure. Some silicon was also detected in the plasma deposited films.     

Plasma polymerization of copper phthalocyanines and application of the plasma polymer films to NO2 gas sensor device

Four copper phthalocyanines without substituent (CuPc) and with chlorine (CuPc-Cl), hydroxymethyl (CuPc-CH₂OH), and phthalimidomethyl substituents (CuPc-CH₂N-[C(O)]₂Ph) were plasma-polymerized to obtain amorphous and thin films having the extended π-electron system. The chemical composition of the plasma polymer films was discussed from the data of the electronic spectra, IR spectra, and XPS spectra. The application of the plasma polymer films was discussed with regard to the NO₂ sensitivity, the NO₂ selectivity, the response time, and the reversibility. Plasma polymerization of CuPc, CuPc-Cl, CuPc-CH₂OH, and CuPc-CH₂OH gives amorphous films having the extended π-electron system. In the plasma polymerization process, a part of the extended π-electron system is broken down. The CH₂OH and CuPc-CH₂N[C(O)]₂Ph substituents contribute to minimizing the degradation. The Cu atoms liberated from the chelation in the plasma polymerization process exist as CuO in the deposited films. The plasma polymer films of CuPc-CH₂OH and CuPc-CH₂N[C(O)]₂Ph show good sensitivity to NO₂ molecules. With regard to the sensitivity, the selectivity, the response time and the reversibility, the plasma polymer films are applicable materials to the NO₂ sensor device. © 1995 John Wiley & Sons, Inc.     

Preparation of plasma-polymerized membranes from I-(trimethylsilyl)-I-propyne and gas permeability through the membranes

Summary Plasma-polymerized membranes for gas separation were prepared from 1-(trimethylsilyl)-1-propyne. The permeation data of He, H₂ 0₂, N₂, CO₂, and CH₄ through the membranes showed plasma-polymerized 1-(trimethylsilyl)-1-propyne had high permselectivity but low permeability compared with poly[l-(trimethylsilyl)-1-propyne]. This behavior is considered to be due to the crosslinking structure of the plasma-polymerized membrane. The correlation between plasma polymerization conditions and the membrane performance was studied. The optimum condition at which the deposition rate of the plasma polymer is maximized agreed with the optimum value to yield maximum separation factor of gases through the membrane.     

Carbon molecular sieve membranes derived from Matrimid® polyimide for nitrogen/methane separation

A commercial polyimide, Matrimid® 5218, was pyrolyzed under an inert argon atmosphere to produce carbon molecular sieve (CMS) dense film membranes for nitrogen/methane separation. The resulting CMS dense film separation performance was evaluated using both pure and mixed N₂/CH₄ permeation tests. The effects of final pyrolysis temperature on N₂/CH₄ separation are reported. The separation performance of all CMS dense films significantly exceeds the polymer precursor dense film. The CMS dense film pyrolyzed at 800 °C shows very attractive separation performance that surpasses the polymer membrane upper bound line, with N₂ permeability of 6.8 Barrers and N₂/CH₄ permselectivity of 7.7 from pure gas permeation, and N₂ permeability of 5.2 Barrers and N₂/CH₄ permselectivity of 6.0 from mixed gas permeation. The temperature dependences of permeabilities, sorption coefficients, and diffusion coefficients of the membrane were studied, and the activation energy for permeation and diffusion, as well as the apparent heats of sorption are reported. The high permselectivity of this dense film is shown to arise from a significant entropic contribution in the diffusion selectivity. The study shows that the rigid ‘slit-shaped’ CMS pore structure can enable a strong molecular sieving effect to effectively distinguish the size and shape difference between N₂ and CH₄.     

Synthesis and polymerization of fluorinated,chlorinated and deuterated vinyl carbonates

The present paper deals essentially with the synthesis of new fluorinated and chlorinated poly(vinylcarbonates). Vinyl carbonates, CH₂=CH-O-CO₂R (where R=CH₂CCl₃, CH₂CF₃, C₂H₄C₆F₁₃ and CD₃) were first prepared by reacting vinyl chloroformate with the corresponding alcohols. Their structures were identified by¹³C NMR. The action of ultraviolet light on these monomers resulted in the corresponding polycarbonates, the refractive indexes and Tg of which were measured. Polycarbonates possess Tg values between those of polyacrylates and polymethacrylates which contain the same substituents.     

Growth and characterization of fluorocarbon thin films grown from trifluoromethane (CHF3) using pulsed‐plasma enhanced CVD

Trifluoromethane (CHF₃) was used as a precursor gas in pulsed‐plasma enhanced CVD to deposit fluorocarbon films onto Si substrates. The film composition, as measured by X‐ray photoelectron spectroscopy (XPS) of the C1s peak, was observed to change as the plasma duty cycle was changed by varying the plasma off‐time; this offers a route to control the molecular architecture of deposited films. FTIR results indicate that the film is primarily composed of CF_x components, with little or no C H incorporation into the film. The rms roughness of the films is extremely low, approaching that of the Si substrate; the low growth rate and consequent high‐power input/thickness is believed to be partly responsible. CHF₃ produces films with higher % CF₂ compared to other hydrofluorocompound (HFC) monomers (CH₂F₂ and C₂H₂F₄). However, the deposition kinetics for all three HFC gases display similar trends. In particular, at a fixed on‐time of 10 ms, the deposition rate per pulse cycle reaches a maximum at an off‐time of approximately 100 ms. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 842–849, 2000