Immobilization of enzyme and antibody on ALD-HfO2-EIS structure by NH3 plasma treatment

Thin hafnium oxide layers deposited by an atomic layer deposition system were investigated as the sensing membrane of the electrolyte-insulator-semiconductor structure. Moreover, a post-remote NH₃ plasma treatment was proposed to replace the complicated silanization procedure for enzyme immobilization. Compared to conventional methods using chemical procedures, remote NH₃ plasma treatment reduces the processing steps and time. The results exhibited that urea and antigen can be successfully detected, which indicated that the immobilization process is correct.     

Fabrication of superhydrophobic transparent cyclic olefin copolymer (COC)-SiO2 nanocomposite surfaces

A superhydrophobic cyclic olefin copolymer (COC) nanocomposite coating was produced with a very simple and easy method. Self-cleaning superhydrophobic COC surfaces were obtained by only adding surface hydrophobized SiO₂ nanoparticles by dip coating method. The influence of concentration of SiO₂ and the coating temperatures on the wettability of the surfaces were investigated. The surface wettability of the coatings was examined with the contact angle measurements and the surface roughness and morphology were analyzed by using atomic force microscope and scanning electron microscopy analysis. Surfaces with certain amounts of COC and SiO₂ showed superhydrophobic character with high water contact angle of 169⁰. Also, the obtained superhydrophobic surfaces show superior water repellent, high transparency, and self-cleaning characteristics.     

Surface modification of poly(tetrafluoroethylene) film by plasma graft polymerization of sodium vinylsulfonate

Poly(tetrafluoroethylene) (PTFE) surface was modified by the graft polymerization of sodium vinylsulfonate, and the chemical composition of the graft-polymerized PTFE surface was analyzed by X-ray photoelectron spectroscopy. Peroxides were formed on the PTFE surface by a combination procedure of argon plasma irradiation and air exposure, and the graft polymerization of sodium vinylsulfonate was initiated by the peroxide groups at 65–80°C. The peroxide concentration is 3 × 10⁺¹³ to 5 × 10⁺¹³ numbers/cm². The average degree of polymerization of the graft polymers was 3.4 × 10³. The graft polymer is distributed over the PTFE surface, but part of the PTFE surface remains uncovered. The coverage with the graft polymer is 43%. The PTFE surface graft polymerized with sodium vinylsulfonate was somewhat hydrophilic, but the hydrophilicity was lower than that of the PTFE surface modified by plasma treatment. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 77–84, 1997     

Plasma assisted immobilization of poly(ethylene oxide) onto fluorocarbon surfaces

Different plasma-assisted procedures were compared with respect to the immobilization of poly(ethylene oxide) (PEO) and poly(ethylene-block-propylene) triblock copolymers (PEO-PPO-PEO) on top of thin plasma-deposited fluorocarbon layers. The fluorocarbon substrate was used as a model system for the common poly(tetrafluoroethylene) as it provides several advantages to apply surface-selective analytical methods. The fixation of pre-adsorbed PEO-PPO-PEO by argon plasma treatments on the fluorocarbon surface was found to produce less homogeneous coatings probably due to the insufficient adsorption of the triblock-copolymers on the substrate. More effective PEO coverage of the fluorocarbon surface was achieved by O₂-plasma initiated graft polymerization of PEO-dimethacrylate (M_w = 400 g/mol) and PEO-monoacrylate (M_w = 1000 g/mol) from solutions or melts. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were utilized for a detailed study of the modified surfaces. The efficiency of PEO-coatings with respect to the reduction of protein adsorption onto the hydrophobic fluorocarbon layer was demonstrated with the example of the adsorption of fibrinogen. The adsorbed amount of this protein was determined based on spectroscopic ellipsometry.     

Analysis of annealed thin polymer films prepared from dichloro(methyl)phenylsilane by plasma polymerization

Thin plasma polymer films were deposited from a mixture of dichloro(methyl)phenylsilane (DCMPS) vapor and gaseous hydrogen in an rf (13.56 MHz) capacitive coupling deposition system on pieces of silicon wafers. Some of samples were annealed in a vacuum to temperatures ranging from 450 to 700°C. The chemical composition, structure, and surface morphology of the annealed samples and those stored in air at room temperature were studied by FTIR, XPS, SEM, and optical microscopy. The thermal stability and decomposition of the plasma polymer with increasing temperature were characterized using thermogravimetry together with mass spectrometry. The plasma polymer was stable to a temperature of 300°C. Above that temperature, the material started to decompose together with additional crosslinking due to the incorporation of extra oxygen atoms forming new siloxane bonds. The plasma polymer was tough at room temperature but much more brittle after annealing. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2106–2112, 2001     

Vinyl polymerization: 414. Polymerization of vinyl monomer initiated by poly(N,N,N-trimethyl-N-2-methacryloxyethyl)ammonium chloride

The polymerization of vinyl monomer initiated by an aqueous solution of poly(N,N,N-trimethyl-N-2-methacryloxyethyl)ammonium chloride (poly(Q-DMAEM-CI) has been carried out at 85°C. The effects of the amounts of vinyl monomer, poly(Q-DMAEM-CI) and water on the conversion of vinyl monomer have been studied. The overall activation energy in the polymerization of MMA is estimated as 41.9 kJ mol^?1. The polymerization proceeds through a radical mechanism. The location in which the polymerization occurs is discussed. The selectivity for vinyl monomer is explained by ‘the concept of hard and soft hydrophobic areas and monomers’.     

Electrochemical properties of polypropylene membranes modified by the plasma polymerization coating of SO2/acetylene

Polypropylene membranes were modified by the plasma etching of SO₂, SO₂? O₂, or SO₂? H₂O, followed by the plasma polymerization coating of SO₂/acetylene. The conditions for SO₂ plasma etching were optimized by the measurement of the ion‐exchange capacity (IEC) as a function of the plasma‐etching power (10–30 W), gas pressure (40–60 mTorr), and treatment time (15–120 s). For the plasma etching of SO₂? O₂ and SO₂? H₂O, only the pressure ratio (SO₂/O₂ and SO₂/H₂O) was optimized under the optimized conditions determined from SO₂ plasma etching. Plasma etching was then combined with the plasma polymerization coating of SO₂/acetylene, for which the conditions were again optimized by the measurement of the IEC as a function of the plasma power (10–40 W), chamber pressure (50–200 mTorr), SO₂/acetylene ratio (15/135–60/90), and treatment time (0–10 min). Next, the electrical resistance and water uptake were evaluated. The modified membranes were also analyzed with scanning electron microscopy, whereas plasma polymer coatings were characterized with Fourier transform infrared/attenuated total reflection. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3692–3699, 2006     

Grafting of poly(N‐isopropylacrylamide) onto nylon and polystyrene surfaces by atmospheric plasma treatment followed with free radical graft copolymerization

Stimuli‐responsive polymer materials (SRPs) have potential uses in drug delivery, tissue engineering, bioreactors, and cell‐surface adhesion control. Temperature‐responsive surfaces were fabricated by grafting poly(N‐isopropylacrylamide) (PNIPAM) onto nylon and polystyrene surfaces via a new procedure, i.e., He atmospheric plasma treatment followed by free radical graft copolymerization. The atmospheric plasma exhibits the activation capability to initiate graft copolymerization. The procedure is suitable for integration into a continuous manufacturing process. To reduce homopolymerization and enhance graft yield, Mohr's salt was added. The graft of PNIPAM was confirmed by Fourier transform infrared spectroscopy and atomic force microscopy. Dramatic water contact angle increase was found for PNIPAM‐grafted polymers at about 32°C, indicating the temperature sensitivity of the grafted surface, i.e., the change of surface from hydrophilic to hydrophobic when temperature increases above the lower critical solution temperature (LCST). The addition of Mohr's salt enhances the grafting reaction and the magnitude of temperature sensitivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3614–3621, 2007     

Plasma etching and plasma polymerization coating of carbon fibers. Part 2. Characterization of plasma polymer coated carbon fibers

Unsized AS-4 carbon fibers were subjected to RF plasma etching and/or plasma polymerization coating in order to enhance their adhesion to vinyl ester resin. Ar, N₂ and O₂ were utilized for plasma etching, and acetylene, butadiene and acrylonitrile were used for plasma polymerization coating. Etching and coating conditions were optimized in terms of plasma power, treatment time, and gas (or monomer) pressure by measuring the interfacial adhesion strength. Interfacial adhesion was evaluated using micro-droplet specimens prepared with vinyl ester resin and plasma etched and/or plasma polymer coated carbon fibers. Surface modified fibers were characterized by SEM, XPS, FT-IR, α-Step, dynamic contact angle analyzer (DCA) and tensile strength measurements. Interfacial adhesion between plasma etched and/or plasma polymer coated carbon fibers and vinyl ester resin was reported previously (Part 1), and characterization results are discussed is this paper (Part 2). Gas plasma etching resulted in preferential etching of the fiber surface along the draw direction and decreased the tensile strength, while plasma polymer coatings altered neither the surface topography of fibers nor the tensile strength. Water contact angle decreased with plasma etching, as well as with acrylonitrile and acetylene plasma polymer coatings, but did not change with butadiene plasma polymer coating. FT-IR and XPS analyses revealed the presence of functional groups in plasma polymer coatings.     

Surface modification of polyester and polyamide fabrics by low frequency plasma polymerization of acrylic acid

In this study, the surface characteristics of polyester and polyamide fabrics were changed by plasma polymerization technique utilizing acrylic acid as precursor. This monomer was used to produce hydrophilic materials with extended absorbency. The hydrophilicity, total wrinkle recovery angle (WRA°) and breaking strength of the fabrics were determined prior and after plasma polymerization treatment. The modification of surfaces was carried out at low pressure (<100 Pa) and low temperature (<50°C) plasma conditions. The effects of exposure time and discharge power parameters were optimized by comparing properties of the fabrics before and after plasma polymerization treatments. It was shown that two sides of polyester fabric samples were treated equally and homogeneously in plasma reactor. For polyester fabrics, the minimum wetting time, 0.5 s, was observed at two plasma processing parameters of 10 W–45 min and 10 W–20 min, where untreated fabric has a wetting time of 6 s. For polyester fabrics, the maximum value was obtained at 60 W–5 min with the wrinkle recovery angle of 306° where the untreated fabric has 290°. The optimum plasma conditions for polyamide fabrics were determined as 30 W–45 min where 2 s wetting time was observed. Wrinkle recovery angle of untreated polyamide fabric was 264°. In this study, after plasma polymerization of acrylic acid, wrinkle recovery angle values were increased by 13%. No significant change was observed in breaking strength of both fabrics after plasma treatment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2318–2322, 2007     

Synthesis,microstructure and property characterization of Mo4Y2Al3B6 ceramic fabricated by spark plasma sintering

Polycrystalline Mo₄Y₂Al₃B₆ ceramic (92.84 wt% Mo₄Y₂Al₃B₆ and 7.16 wt% MoB) was prepared by spark plasma sintering at 1250 ℃ under 30 MPa using Mo, Y, Al, and B as starting materials. The dense sample obtained has a high relative density of 96.6 %. The average thermal expansion coefficient is 8.38 × 10^?6 K^?1 in the range of 25–1000 ℃. The thermal diffusivity decreases from 6.50 mm²/s at 25 °C to 4.33 mm²/s at 800 °C. The heat capacity, thermal conductivity, and electrical conductivity are 0.30 J·g^?1·K^?1, 11.73 W·m^?1·K^?1, and 0.66 × 10⁶ Ω^?1·m^?1 at 25 °C, respectively. Vickers hardness with increasing load in the range of 10–300 N at room temperature decreases from 10.82 to 9.49 GPa, and the fracture toughness, compressive strength, and flexural strength are 5.14 MPa·m^1/2, 1255.14 MPa, and 384.82 MPa, respectively, showing the promising applications as structural-functional ceramics.     

Atom transfer radical polymerization of styrene initiated by 2-(4-chloromethyl-phenyl)-benzoxazole with high activity and fluorescent property

Functionalized polystyrene (PSt) was synthesized utilizing atom transfer radical polymerization (ATRP), which was conducted by using 2-(4-chloromethyl-phenyl)-benzoxazole (CMPB) as initiator, CuCl/PMDETA as catalyst, and cyclohexanone as solvent. The mechanism of ATRP was proved by characterizing the structure of PSt via ¹H NMR and preparing of PSt-b-PMMA block copolymer. The polymerization showed first order with respect to monomer concentration and relatively narrow polydispersity (M_w/M_n range from 1.30 to 1.50). Factors such as different reaction temperatures, mole ratio of monomer to initiator and so on, which can affect the ATRP system, were discussed in the paper. Moreover, CMPB showed high activity and could initiate styrene polymerization even at ambient temperature. The optical property of initiator was well preserved in the obtained PSt, and the end-functionalized PSt exhibited strong fluorescent emission at 351 nm.     

Modification of poly(tetrafluoroethylene) and copper foil surfaces by graft polymerization for adhesion improvement

Thermal graft polymerization-induced lamination of surface-modified copper foil to surface-modified poly(tetrafluoroethylene) (PTFE) film was achieved in the presence of an epoxy resin adhesive and glycidyl methacrylate (GMA) monomer, or in the presence of GMA and hexamethylenediamine (HEDA). The copper foil surfaces were pretreated with an organosilane coupling agent (SCA), such as (3-mercaptopropyl)trimethoxysiane, 3-(trimethoxysilyl)propyl methacrylate, or N¹-[3-(trimethoxysilyl)propyl]diethylene-triamine. The silanized copper foils were subjected to brief Ar plasma treatment and subsequently to UV-induced graft polymerization with GMA (the Cu-SCA-g-GMA surface). Surface modification of PTFE film included Ar plasma treatment alone, or Ar plasma pretreatment followed by UV-induced graft polymerization with GMA (the GMA-g-PTFE surface). The modified surfaces and interfaces were characterized by X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. The Cu-SCA-g-GMA/epoxy resin-GMA/PTFE or Cu-SCA-g-GMA/GMA–HEDA/GMA-g-PTFE laminates exhibited T-peel adhesion strengths in excess of 9 N/cm and the joints delaminated by cohesive failure inside the bulk of the PTFE film. The strong adhesion in these Cu foil-PTFE laminates is attributable to the fact that the GMA chains are covalently tethered on both the PTFE and the silanized Cu surfaces, as well the fact that these grafted GMA chains are covalently incorporated into the highly crosslinked network structure of the adhesive at the interphase.     

Gel-casting of transparent magnesium aluminate spinel ceramics fabricated by spark plasma sintering (SPS)

In this paper, a transparent magnesium aluminate spinel ceramic was fabricated through the newest colloidal gel casting method, using a synthetic powder with the average particle size of 90 nm and Isobutylene-Maleic Anhydride (ISOBAM) additive. ISOBAM served as both a dispersant and a gelation agent to achieve a dense body. Also, the suspension rheological behavior was optimized by the solid loading of 85 wt%, the additive content of 0.7 wt%, and the gelation time of 350 s. This led to a green body with a density equal to 65% of theoretical density and the green strength of 14.48 MPa. The results revealed that the reduction of porosity and the uniform distribution of pores in the green body (smaller than half of the initial powder particle size, 35 nm), as accompanied by spark plasma sintering (SPS), resulted in the final body density of 99.97%, as well as the high in-line transmittance of 86.7% at the wavelength of 1100 nm.     

Densification,microstructures, and mechanical properties of (Zr,Ti)(C,N) ceramics fabricated by spark plasma sintering

Dense (Zr, Ti) (C, N) ceramics were fabricated by spark plasma sintering (SPS) at 1900–2000 °C using ZrC, TiCN and ZrH₂ powders as raw materials. A single Zr-rich (Zr, Ti)(C, N) solid solution was formed in Zr_0.95Ti_0.05C_0.975N_0.025 and Zr_0.80Ti_0.20C_0.90N_0.10 ceramics (nominal composition). A Ti-rich solid solution appears in Zr_0.50Ti_0.50C_0.75N_0.25 ceramics. The coaddition of TiCN and ZrH₂ promoted the densification of (Zr, Ti) (C, N) ceramics by forming solid solutions and carbon vacancies, which could reduce critical resolved shear stress (CRSS) and promote carbon and metal atom diffusion. ZrC-45 mol% TiCN-10 mol% ZrH₂ (raw powder composition) possesses good comprehensive mechanical properties (Vickers hardness of 24.5 ± 0.9 GPa, flexural strength of 503 ± 51 MPa, and fracture toughness of 4.3 ± 0.2 MPa·m^1/2), which reach or exceed most ZrC-based (Zr, Ti) C and (Zr, Ti) (C, N) ceramics in previous reports.     

Oxygen plasma modification of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) film surfaces for tissue engineering purposes

Plasma glow‐discharge application is known as a technique to coat or modify the surfaces of various materials. In this study, the influence of oxygen rf‐plasma treatment on surface and bulk properties of a biological polyester, poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), were studied by determining water content and water contact angle, and by using X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The plasma‐treated films absorbed more water than the untreated film, and the absorbance increased with the total power applied. The water contact angles decreased and O/C atomic ratio increased on treatment, indicating that the material became more hydrophilic due to increases in the oxygen‐containing functional groups on the surface of the polymer. A direct relation could be observed when the O/C ratio was plotted against the total power applied (treatment duration × treatment power). SEM revealed a visual record of surface modification, the extent of which increased with increased total power. It was thus possible to alter the surface chemistry and relevant properties of the polymer film using oxygen plasma as a tool. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1285–1289, 2003     

Propylene polymerization by using TiCl4 catalyst supported on solvent‐activated Mg(OEt)2

Solvent activation of Mg(OEt)₂ in ethanol with carbon dioxide was carried out in a 1‐L three‐neck flask under nitrogen atmosphere, to investigate structural changes of Mg(OEt)₂ support. During activation of Mg(OEt)₂ by ethanol and CO₂, a suspension mixture was converted to a clear solution and CO₂ was inserted into the Mg? O bond of Mg(OEt)₂, to form magnesium ethyl carbonate. The solid supports were obtained from the removal of solvents by heating, during which CO₂ split off from the magnesium ethyl carbonate between 100 and 150°C. The structural changes of the obtained supports and the corresponding catalysts were checked by IR and TGA. The polymerization behavior of propylene with the catalyst and morphology of the obtained polymer were also examined. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 460–467, 2001     

Surface modification of polyethylene by plasma pretreatment and UV‐induced graft polymerization for improvement of antithrombogenicity

The purpose of this study was to enhance blood compatibility of polyethylene (PE) films. Glycidyl methacrylate (GMA) was grafted onto the surface of PE by Ar plasma pretreatment and UV‐induced graft polymerization without photo‐initiator, then heparin was immobilized onto the poly (glycidyl methacrylate) segments. The surface compositions and microstructure of GMA graft polymerized PE films were studied by X‐ray photoelectron spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transfer Infrared (ATR‐FTIR) spectroscopy. It was confirmed that heparin was successfully immobilized onto the surface of PE films by XPS analysis. The antithrombogenicity of the samples was determined by the activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), and plasma recalcification time (PRT) tests and platelet adhesion experiment. Results indicated that the antithrombogenicity of modified PE was improved remarkably. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2014–2018, 2004     

Encapsulation of TiO2 by emulsion polymerization with methyl metacrylate (MMA)

Summary This paper presents a methodology of encapsulation of TiO₂ (Titanium dioxide) by emulsion polymerization on the proposal to modify the physical-chemical properties of the pigment surface. In the proposed methodology the TiO₂ was previously modified by isopropoxy-titanium-tri-isostearate, before being encapsulated by emulsion polymerization using Methyl Methacrylate as monomer. The effects of the polymerization process, type of initiator and monomer concentration in the efficiency of encapsulation were studied. The encapsulated pigment was characterized by Thermogravimetric Analysis (TGA), Light Scattering (LS) and Transmission Electron Microscopy (TEM).     

Microstructure and properties of Al2O3-TiC-Ti3SiC2 composites fabricated by spark plasma sintering

Abstract

Abstract

Highly densified Al₂O₃-TiC-Ti₃SiC₂ composites were fabricated by spark plasma sintering technique and subsequently characterised. From fracture surface observation, it is found that Al₂O₃ is 0·2-0·4?μm, TiC is 1-1·5?μm and Ti₃SiC₂ is 1·5-5?μm in grain size. With the increase in Ti₃SiC₂ volume contents, Vickers hardness of the composites decreases because of the low hardness of monolithic Ti₃SiC₂. The fracture toughness rises remarkably when the contents of Ti₃SiC₂ increase, which is attributed to the pullout and microplastic deformation of Ti₃SiC₂ grains. At the same time, the flexural strength of the composites shows a considerable improvement as well. The electrical conductivity rises significantly as the Ti₃SiC₂ contents increase because of the formation of Ti₃SiC₂ network and the increase in conductive phase contents.