Relative Rates for Plasma Homo- and Copolymerizations of a Homologous Series of Fluorinated Ethylenes

The relative rates of plasma homo- and Copolymerizations of ethylene, vinyl fluoride, vinylidene fluoride, trifluoroethylene and tetrafluoroethylene (VF _x , x = 0–4, respectively) were determined in an rf, capacitively coupled, tubular reactor with external electrodes using identical plasma parameters. The deposition rates for VF _x (x = 1–3) and 20 different monomer blends, when plotted versus the F/C ratios of the monomers or monomer blends, followed a concave-downward curve situated above the straight-line joining the rates for VF₀ and VF₄. The deposition rates for VF _m /VF _n blends (m = 3 or 4; n = 0–2) likewise yielded concave-downward curves situated above the straight lines joining the rates for the respective monomers; the rates for VF _m /VF _n blends (m = 0 or 1; n = 1 or 2) yielded concave-upward curves situated below the straight lines joining the rates for the respective monomers; while the rates for VF₃/VF₄ blends fell along the straight line joining the rates for VF₃ and VF₄. The mechanisms for plasma (co) polymerizations of VF _x monomers responsible for the wide range of relative deposition rates remain to be elucidated.     

Plasma polymerization of fluoromethanes

Methane and fluoromethanes (CH_nF_4−n, 1 ≤ n ≤ 3) were subjected to an rf glow discharge plasma. All the fluoromethanes (including methane) polymerized in the plasma and formed thin films. The deposition rate of the fluoromethanes depended on their monomer structure: CH₂F₂, of which the F/H ratio is unity, showed the greatest deposition rate. The elimination of H and F atoms as H—F was found to be a key factor for the polymerization of fluoromethanes. The chemical composition of the polymerized film, measured with X-ray photoelectron spectroscopy and glow discharge emission spectroscopy, was also found to be strongly dependent on monomer structure. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2043–2050, 1998     

Emulsion copolymerization of tetrafluoroethylene and propylene with redox system containing tert-butylperbenzoate. II. Polymerization mechanism

Emulsion copolymerization of tetrafluoroethylene (TFE) and propylene (P) initiated by trilon-rongalite catalytic system containing tert-C₄H₉OH, initial monomer mixture, emulsifier (C₇F₁₅COONH₄) concentration, and monomer mixture/water ratio on the polymerization rate (R) and molecular weight (M?_n ) was investigated. Both R and M?_n increased considerably with TFE content in monomer mixture up to 75 mol %. Alternating rubber-like copolymers in a wide range of initial monomer mixture (from 55–85 mol %) were obtained. The reactivity ratio was found to be r_TFE = 0.005 ± 0.04 and r_p = 0.17 ± 0.07. Above the critical miscelle concentration, the effects of the initiating system Is and emulsifier Cs on R and M?_n were found to obey the following relations: according to which emulsion copolymerization proceeds by the I case of Smith-Ewart theory. Polymerization mechanism of the reaction studied was suggested. The copolymerization is mainly terminated by degradative chain transfer of the propagating radicals to propylene. © 1994 John Wiley & Sons, Inc.     

Radical homo- and copolymerizations of methyl α-trifluoroacetoxyacrylate

Radical homo- and copolymerizations of methyl α-trifluoroacetoxyacrylate (MTFAA) are studied by using azo initiators at 40 and 60°C. The rate of the homopolymerization of MTFAA was lower than that of methyl α-acetoxyacrylate. Monomer reactivity ratios (r), and Q and e values were estimated to be r₁ = 0.03, r₂ = 0.27, Q₁ = 0.65, and e₁ = 1.38 from the copolymerization of MTFAA (M₁) and styrene (M₂) at 60°C. Preferential crosspropagation was observed in particular in the copolymerization of MTFAA and α-methylstyrene. The influence of replacing the hydrogens of the acetoxy moiety of the acyloxyacrylate with the fluorines upon the copolymerization reactivity is discussed on the basis of the ¹³C-NMR chemical shift of various acyloxyacrylates. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3537–3541, 1997     

Synthesis and characterization of epoxy functionalized cooligomers based on chlorotrifluoroethylene and allyl glycidyl ether

The synthesis of functionalized fluorocooligomers based on chlorotrifluoroethylene (CTFE) and allyl glycidyl ether (AGE) under radical copolymerization is presented. The compositions of comonomers in the cooligomers were determined by three different analyses viz: from ¹H and ¹⁹F NMR spectroscopy by using 1,3‐bis(trifluoromethyl) benzene as the external standard, epoxy equivalent weight value, and elemental analyses. The compositions determined by three methods were matching reasonably well and showed that the resulting poly(CTFE‐co‐AGE) cooligomers exhibit a tendency for alternation. The distribution of the monomers in the cooligomers was proposed based on the assessment of the reactivity ratios, r_i, of both comonomers. These values were determined from the kinetics of radical copolymerization of CTFE with AGE from Fineman‐Ross, Kelen‐Tudos, and extended Kelen‐Tudos methods which led to the assessment of the average reactivity ratios as: r_CTFE = 0.20 ± 0.03 and r_AGE = 0.15 ± 0.08 at 74 °C. The lower M_n values substantiated the formation of cooligomers rather than copolymers. The formation of cooligomers was attributed to the chain transfer to AGE (by hydrogen abstraction from AGE) from the allylic transfer. The poly(CTFE‐co‐AGE) cooligomers were soluble in most of the common organic polar solvents. An optimization of cooligomer yields was investigated by using ethyl vinyl ether as a third comonomer and from different initiators. The thermal stabilities of the cooligomers, obtained by thermal gravimetric analysis, showed a 5% weight loss at temperatures over 225 °C under air. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3587–3595, 2010     

Analysis of PPMMA films from oxygen plasma using X-ray photoelectron spectroscopy

Plasma polymerized methyl methacrylate (PPMMA) films have been synthesised on silicon substrates in RF glow discharge using oxygen plasma. The electron beam delineation sensitivity of the PPMMA films has been studied systematically by varying oxygen and monomer flow rates. X-ray photoelectron spectroscopy (XPS) analysis clearly illustrates how C/O ratio in the films determines the properties of PPMMA films as electron beam resist. © 1994 John Wiley & Sons, Inc.     

氩等离子体后辉光区对聚四氟乙烯膜表面的优化改性

在理想管式反应器中, 采用Langmuir双电子探针和电子自旋共振(ESR)诊断技术分别定量测定了氩等离子体场中各活性物种的轴向分布, 并利用氩等离子体放电区及后辉光区对聚四氟乙烯(PTFE)进行了表面改性. 通过接触角测量、扫描电子显微镜和X 射线光电子能谱分析比较了改性前后常规及后辉光氩等离子体对PTFE表面结构及性能的影响. 结果表明, 氩等离子体中电子及离子浓度随轴向距离的增大迅速降低, 30 cm后接近于0, 而自由基浓度则降低缓慢, 40 cm处仍为初始浓度的96%. 氩等离子体放电功率、处理时间和气体流量强烈影响着PTFE表面润湿性的改善效果. 后辉光区因抑制电子和离子的刻蚀作用, 强化自由基反应, 使改性效果远优于常规氩等离子体. 经氩等离子体后辉光区短时间(30 s)处理后, PTFE表面化学成分发生了变化, F/C原子比从3.27降至2.30, O/C原子比从0.02增至0.09. 脱氟作用和含氧基团(如CO)的引入是有效改善PTFE表面润湿性的关键因素.     

Molecular Engineering of Surfaces by Plasma Copolymerization and Enhanced Cell Attachment and Spreading

The plasma copolymerization of acrylic acid and methyl vinyl ketone with 1,7-octadiene is reported. A range of surfaces including hydrocarbon plasma polymer, carbonyl-containing plasma copolymer and carboxyl-containing plasma copolymers have been prepared and characterized by means of X-ray photoelectron spectroscopy. The stability of these surfaces in water has been assessed at 37°C. The influence of their functional group chemistries on the attachment and spreading of osteoblast-like (ROS 17/2.8) and bone marrow stromal cells (BMSC) has been explored. The data reported show a strong correlation between the carboxyl group and the attachment and spreading of both ROS cells and BMSC. This relationship has been explored in some detail with the ROS cells. Actin-staining by direct immunofluorescence was used to visualize changes in cytoskeleton of ROS cells with substratum chemistry. As the concentration of the carboxyl groups increased cell number and cell spreading were notably enhanced. As few as 5 carboxyls per 100 carbons were sufficient to support good attachment and with cells showing well-defined polygonal cell morphology. Although cells attached to a hydrocarbon plasma polymer surface these cells had failed to spread. The attachment and spreading of BMSC were compared on a carboxyl-containing surface and on a hydrocarbon surface. There was a more marked difference in the number of cells that had attached to these two surfaces (cf. ROS cells). The spreading on the carboxyl surface was much more typical of BMSC. Results from an extended culture using primary cultures of bone marrow cells (BMC) are reported. These cells were not trypsinized and appear to be less sensitive to differences in surface chemistry (cf. BMSC). Even so, the results at 10 days indicate much greater biosynthetic activity on the carboxyl-containing surface.     

XPS Analysis of the Aging of Thin,Adhesion Promoting,Fluorocarbon Treatments of DC Plasma Polymers

Plasma polymer treatment of aluminum alloys has recently been shown to improve adhesion of primer coatings, thereby reducing the corrosion of thusly protected panels to the levels afforded by conventional chromate conversion coating. One particular plasma polymer system, comprised of a 50 nm trimethylsilane DC plasma polymer capped by an ultrathin layer modified by DC hexafluoroethane plasma treatment, has shown tremendous adhesion increases to a wide variety of primers, yielding a coating that is virtually unremovable with conventional stripping applications. An application window was empirically deduced regarding this improved adhesion, indicating that the primer needed to be applied within 5 days of plasma treatment to display the tenacious adhesion to panels. In an effort to elucidate the differences between fresh and aged panels, an X-ray photoelectron spectroscopy (XPS) time study of this system was undertaken. Some direct correlation to this time frame was observed in the XPS data, indicating that a particular fluorocarbon structure in the films modified upon continued atmospheric exposure, rearranging the local bonding environment by introducing additional C—C bonding with an increase in oxygen incorporation.     

Fluorinated-plasma coating on polyhydroxyalcanoate PHBV: Effect on the biodegradation

Poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) was covered with an hydrophobic layer from plasma polymerization of tetradecafluorohexane, octadecafluorooctane, 3,3,4,4,5,5,6,6,6-nonafluoro-hex-1-ene and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-oct-1-ene. The water contact angle increased from 74° for untreated films to 98° for the treated films and the surface energy decreased from 40.9 to 18.8 mJ m⁻². XPS analysis showed the introduction of 54% fluorine and 3-7% oxygen, the binding energies were assigned to chemically differently bonded carbon atoms. CF₂/CF₃ molar ratio in plasma layers was lower than that in the monomers due to molecular fragmentation, however the extent of monomer structure retention in PFH, PFO saturated chains is higher than in NFH, TDFO unsaturated chains. Biodegradation tests under aerobic conditions showed that the fluorinated plasma layer inhibited the biodegradation of the PHBV film underneath.     

Biofouling-resistance expanded poly(tetrafluoroethylene) membrane with a hydrogel-like layer of surface-immobilized poly(ethylene glycol) methacrylate for human plasma protein repulsions

In general, it is a challenge to control the highly polar material grafting from the chemically inert Teflon-based membrane surface. This work describes the surface modification and characterization of expanded poly(tetrafluoroethylene) (ePTFE) membranes grafted with poly(ethylene glycol) methacrylate (PEGMA) macromonomer via surface-activated plasma treatment and thermally induced graft copolymerization. The chemical composition and microstructure of the surface-modified ePTFE membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), contact angle, and bio-atomic force microscopy (bio-AFM) measurements. Biofouling property of the modified membranes was evaluated by the measurements of the plasma protein (γ-globulin, fibrinogen, or albumin) adsorption determined using an enzyme-linked immunosorbent assay (ELISA). In general, the hydrophilicity of the surface of ePTFE membranes increases with increasing the grafting degree of the copolymerized PEGMA. The highly hydrated PEGMA chain on the resulting ePTFE membranes was found to form a surface hydrogel-like layer with regulated coverage in aqueous state, which can be controlled by the content of PEGMA macromonomer in the reaction solution. The relative protein adsorption was effectively reduced with increasing capacity of the hydration for the PEGMA chain grafted on the ePTFE membrane surface. From both results of protein adsorption and platelet adhesion test in vitro, it is concluded that the PEGMA-grafted hydrophilic ePTFE membranes could provide good biofouling resistance to substantially reduce plasma protein and blood platelet fouling on the membrane surface in human body temperature.     

Plasma reactions of self-assembled monolayers to model oxygen atom effects on polymers

The plasma treatment of self-assembled monolayers of octadecyl mercaptan on gold substrates has been investigated as a model for oxygen atom effects on polymers. Both O₂ and H₂O low pressure gas plasmas have been used. X-ray photoelectron spectroscopy has revealed that the two plasma treatments differ from each other in the extent of oxidation and etch rate with O₂ being the more aggressive plasma. The results have confirmed that the plasma modification of organic surfaces involves a balance between surface oxidation and surface etching. The well-defined structure of the monolayer enables quantitation of these atom-substrate reactions. © 1998 John Wiley & Sons, Ltd.     

Emulsion copolymerization of tetrafluoroethylene and propylene with redox system containing tert-butylperbenzoate. I. Polymerization conditions and components

Emulsion polymerization of tetrafluoroethylene and propylene with ammonium perfluorooctanoate, initiated by a redox system containing tert-butylperbenzoate (TBPB) was carried out. The effect of the components of the redox system Is (TBPB, FeSO₄.7H₂O, ethylenediamine tetraacetic acid (EDTA), and CH₂(OH)SO₂Na.2H₂O) on the polymerization rate (R) and molecular weight () was studied. Among redox system components, Fe²⁺ concentration exerts the most significant effect (by power of 0.54) on the polymerization rate. It was found that R ∝ [Is]^0.2–0.54 and M_n ∝ [Is]^0.0–0.1 and polymerization reaction scheme was suggested for the action of the initiating system. The influence of the copolymerization conditions (pressure, temperature, stirring speed, and pH) is also discussed. The apparent activation energy of the reaction was found to be 46.0 kJ/mol. © 1994 John Wiley & Sons, Inc.     

Surface Modification of Poly(tetrafluoroethylene) Films by Plasma Pre-Activation and Plasma Polymerization of Glycidyl Methacrylate

Surface modification of poly(tetrafuoroethylene) (PTFE) film by plasma polymerzation and deposition of glycidyl methacrylate (GMA), in the presence and absence of Ar or O₂ plasma pre-activation, was carried out to enhance the adhesion with polyimides (PI) film in the presence of an epoxy adhesive. For deposition carried out at low RF power, a high epoxide concentration was preserved in the plasma-polymerized GMA (pp-GMA) layer on PTFE (pp-GMA-PTFE). However, high adhesion strength of the PI/pp-GMA-PTFE laminate was obtained only in the presence of O₂ plasma pre-activation of the PTFE substrates prior to plasma polymerization and deposition of GMA. In the absence of any plasma pre-activation or in the presence of Ar plasma pre-activation, the deposited pp-GMA layer on the PTFE surface could be readily removed by solvent extraction. The adhesion enhancement of the PI/pp-GMA-PTFE laminates in the presence of O₂ plasma pre-activation was attributed to the preservation of the epoxide functional groups in the pp-GMA layer, the curing of the GMA chains into the matrix of the epoxy adhesive, and the covalent bonding of the pp-GMA layer on the PTFE surface.     

BiI3-nylon11纳米复合材料的XPS及ATR-IR分析

用X射线光电子能谱法（XPS）测定了BiI₃与nylon11作用生成纳米复合材料后聚合物中酰胺基团的N、O内层能级电子结合能变化,同时用衰减全反射红外光谱法（ATR-IR）研究了BiI₃-nylon11复合材料中BiI₃对尼龙酰胺基团之间氢键作用的影响.结果表明,与纯nylon11聚合物相比,BiI₃-nylon11纳米复合材料中N1s、O1s的结合能要稍高一些;N-H伸缩振动、酰胺I谱带、酰胺II谱带振动频率在X射线照射前均发生显著位移,而X射线照射后没有明显的变化,只是谱带变宽.另一方面,无论X射线照射与否,CH₂伸缩振动基本不变.实验所得结果对于理解聚合物中氢键相互作用及其对复合材料的结构和性能的影响有一定意义.     

Anode Magnetron Enhanced DC Glow Discharge Processes for Plasma Surface Cleaning and Polymerization

The objective of this study was to examine some fundamental factors involved in the design and construction of the anode magnetron dc glow discharge processes as well as its performance in plasma cleaning and polymerization. Those advantages of anode magnetron include the capability of the magnetron to operate at low pressure, as well as decreasing the thickness of cathode dark space, i.e., the negative glow which contains a higher concentration of ions and active species was more closely to the cathode surface, which makes the plasma surface cleaning and polymerization an effective and uniform processes. The deposition rate at a given discharge power is increased by the presence of anode magnetrons, and is also much higher relative to rf and af. The refractive index of dc plasma film at a given polymer thickness (such as TMS, 70 nm, RI: 2.4) is higher than rf, af, and cascade arc plasma (RI: 1.6–1.7).     

Stability and ageing of plasma treated poly(tetrafluoroethylene) surfaces

In this study CO₂, H₂/H₂O and H₂O low pressure plasma treatment of poly(tetrafluoroethylene) (PTFE) foils and of thin plasma deposited fluorocarbon polymer (PDFP) films with a structure close to PTFE was investigated. The properties of the plasma were analyzed by mass spectroscopy (MS) and optical emission spectroscopy (OES). The modified fluorocarbon surfaces were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), fourier transform infrared (FTIR) spectroscopy, spectroscopic ellipsometry, electrokinetic measurements and dynamic contact angle measurements in order to find optimized treatment conditions. The results of the surface modification were compared with respect to the efficiency of the plasma treatment and the stability of the modification effect at different ambient conditions. It was shown that the H₂O plasma treatment is the most effective process for the intended modification. The hydrophobic PTFE surface was converted into a more hydrophilic one. The introduced radicals after the H₂O plasma treatment can be utilized subsequently for post plasma reactions such as grafting processes.     

Effects of polymer architecture and composition on the adhesion of poly(tetrafluoroethylene).

Poly(glycidyl methacrylate), PGMA, chains in linear and arborescent structures were incorporated onto surfaces of poly(tetrafluoroethylene), PTFE, films by hydrogen plasma and ozone treatment and atom transfer radical polymerization. The epoxide groups of the PGMA chains were further reacted with acetic acid (AAc), oxalic acid (XAc), allyl amine (AA), and ethylenediamine (EDN) to introduce hydroxyl and amine groups to the surfaces of the PTFE films. Surface characterizations performed by Fourier Transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the surface modification and the chemical structure. The PGMA chains in arborescent structures show a high effectiveness for the enhancement of the adhesion of PTFE films. The adhesion of PTFE films was also significantly enhanced by ring-opening reactions of the PGMA epoxide groups with acetic acid and amine compounds. A high value of 9.5 N cm(-1) in the optimum 180 degrees peel strength test was observed with PTFE/copper assemblies.