Papers by Keyword: Plasma Polymerization

Abstract: Surface modification of polytetrafluoroethylene (PTFE) fiber by plasma grafting polymerization with acrylamide (AAm) was studied to improve the compatibility between polyacetal (POM) and PTFE. The best modified PTFE manufactured by self-designed plasma polymerization was investigated and denoted as AAm (20wt%)-g (plasma 30min)-PTFE. The grafting polymerization is successful and shown by ESCA spectra of modified PTFE fibers. It is also proved by SEM photographs and the improvement of properties of the POM/PTFE composites. As a result, the friction coefficients, Taber wear factors, and impact strengths of composites with 85wt% of POM and 15wt% of a variety of PTFEs were investigated. The frictional coefficient of POM/ AAm (20wt%)-g (plasma 30min)-PTFE deceased to 0.162; while that of POM/PTFE was 0.174. Taber wear factor of the composite significantly decreased from 5.2 to 1.5 when the PTFE was replaced by AAm-g (plasma)-PTFE. Meanwhile, the impact strength increased from 6.1 kg-cm/cm (POM/PTFE) to 9.3kg-cm/cm (POM/ AAm-g (plasma)-PTFE). Besides, the multi-yield behaviors were found in the Stress-Strain curves of composites with modified PTFE fibers.

Abstract: The non-equilibrium atmospheric pressure Ar plasma was applied for the polymerization of maleic anhydride (MA). The deposited films were analyzed by using Fourier transform infrared spectroscopy (FT-IR) proving the monomer was successfully polymerized with retaining the functional groups. The intensity of optical emission spectroscopy (OES) of the plasma jet was found to become weaker when the monomer was introduced into the jet. This was interpreted as the result of the energy transfer from the metastable Ar to the monomer. It was proposed that the excited MA changed into π-π* transition state to produce dimer biradicals which initiate the polymerization.

Abstract: The technique of plasma polymerization was used in the preparation of the poly (cyanate ester) thin films using 4-methoxyphenol cyanate ester (MPCE), 4-Cumylphenol cyanate ester (CPCE) and 4-phenylphenol cyanate ester (PPCE) as precursors. Different from the conventional thermal polymerization of cyanate ester monomers, the plasma polymerization of three monomers proceeds mainly via the opening of π-bonds of the cyanate ester functional groups which are further formed into a large π-conjugated system. The dielectric properties of the resulting plasma thin films were evaluated and results show that the dielectric constant of the three polycyanurate thin films decreased with increasing frequency, while in contrast, the dielectric loss factor increased with the increasing frequency. The obtained poly (cyanate ester) thin films might be the potential new candidates to be used as intermetallic dielectrics in microelectronics.

Abstract: Hexamethyldisiloxane (HMDSO) thin films coated quartz crystal microbalance (QCM) electrodes have been characterized for the detection of volatile organic compounds (VOCs). The sensitive coatings were plasma polymerized in pure vapor of HMDSO at different flow rates. The QCM based sensors responses were found to be linearly correlated with the concentration of VOCs vapor. It was shown that it is possible to tune the chemical affinity of the sensor by changing the HMDSO flow rate. Contact angle measurements, Fourier transform infrared spectroscopy and scanning electron microscopy were used to study surface wettability, chemical composition and surface morphology of the coated QCM electrodes.

Abstract: A non-equilibrium atmospheric pressure plasma was applied for the polymerization of the methacrylic monomers such as (2-hydroxyethyl methacrylate (HEMA), methacrylic acid (MAA) and butyl methacrylate (BMA)). These monomers were successfully polymerized with retaining the functional groups of ester or acid. The polymerization mechanism was discussed on the basis of the optical emission spectroscopy (OES) of the plasma. It was strongly suggested that the functional groups could be retained in the polymerization proceeds when the HOMO-LUMO gap of the monomer is close to the energy of Ar metastable atom, which initiates the polymerization.

Abstract: The thickness dependent direct current electrical conduction mechanism in plasma polymerized pyrrole (PPPy) monolayer thin films has been discussed in this paper. A parallel plate capacitively coupled glow discharge reactor was used to deposit PPPy thin films at room temperature onto glass substrates. The Fourier Transform Infrared (FTIR) analyses showed that the spectrum of PPPy is very much different than that of the pyrrole monomer and indicated that the monomer has undergone the re-organization during the plasma polymerization. The current density-voltage (J-V) characteristics of PPPy monolayer thin films of different thicknesses indicated an increase in electrical conductivity in the thin films of lower thickness. It is seen that in the low voltage region, the current conduction obeys Ohms law while the charge transport phenomenon appears to be the space charge limited conduction (SCLC) in the higher voltage region. The permittivity, free charge carrier density, and the mobility of the charges of the PPPy monolayer thin films have been calculated from the experimental data of J-V characteristics and found to be 1.07 × 10^-10 C²N^-1m^-2, (3.56 ± 0.01) × 10²² m^-3, (4.4 ± 0.01) × 10^-19 m² V^-1s^-1 respectively.

Abstract: In this work, we report the nanofabrication, optical characterization, and electromagnetic modeling of various nanostructure arrays for localized surface plasmon resonance (LSPR) based biosensing studies. Comparison of the experimental results and simulation outputs of various nanostructure arrays was made and a good correspondence was achieved.

Abstract: In this study, the multi-functional gradient pp-F:TMDSO coating had been successfully developed via power-modulated plasma polymerization. The plasma power and gas flow rate of tetramethyldisiloxane and tetrafluoromethane were well controlled to implement a gradient coating to achieve the mechanical property, transmittance, hydrophobic and oleophobic properties. The coating shows that the pencil hardness of 3H and Scotch tape adhesion of 5B demonstrating the protective function of the coating. The water and oil contact angle are 105° and 31.7° respectively. The coated specimen remains an optical transparency of 90% close to bare PC material. Comparing with the commercialized screen protectors, this coating shows superior protective and anti-fingerprint performance.

Abstract: Polymeric materials have been widely used as flexible substrates and housing parts of modern electronic wares. However, their low hardness and scratch resistance must be improved by additional protective surface coatings, which require not only mechanical durability but also additional functions such as surface hydrophobicity, oleophobicity as well as anti-fingerprint performance. To satisfy these, a power modulated plasma polymerization technique was designed to synthesize a transparent compositional gradient coating on polycarbonate (PC) substrate. Firstly, a constant flow rate of tetramethyldisiloxane (TMDSO) precursor was introduced where higher plasma power was employed to deposit a hard H-C-Si-O bottom layer. The plasma power was then decreased meanwhile admitting increased fluoromethane (CF₄) gas flow as the second precursor to obtain a top layer with low surface energy. The hard bottom layer acts as a strong mechanical support and the top layer gives additional hydrophobicity and oleophobicity. Ultimately, the coating shows that a pencil hardness of 3H and Scotch-tape adhesion of 5B improves its protective function. A water contact angle of 105° and oil contact angle of 31.7° can be obtained. The coated specimen remains an optical transparency of 90% close to bare PC material. Comparing with commercialized screen protectors, the developed coating shows superior protective and anti-fingerprint performance.

Abstract: Polyaniline was synthesized by pulsed plasma polymerization using a theta-pinch device. The process was done using oxygen plasma at a voltage of 20 kV, a pressure of 2 Pa and a discharging current of 125 kA. The number of the plasma shots was varied from 10, 15, 20, 25, to 30 shots. This parameter significantly affected the chemical structures of the synthesized polyanilines as revealed by FTIR spectra. While all synthesized polyaniline exhibited the characteristic peaks of quinoid ring and benzenoid group, the peaks corresponding to the formation of oxygen containing groups was found when high numbers of plasma shots were employed. This also caused the difference in UV-VIS absorption of these polyanilines. The highest conductivity of polyaniline was obtained when 20 shots of oxygen plasma were used. At this condition, polyaniline had a semi-crystalline structure and the thermal decomposition temperature at 262oC.