A large research reactor for performingdielectric barrier discharge (DBD) experiments at atmospheric pressure (AP) has been used with argon (Ar) carrier gas under constant plasma conditions (f ¼ 20 kHz, V a (f) ¼ 8 kV p-p ¼ 2.8 kV rms ). Various permanent gases (H 2 , O 2 , N 2 , light hydrocarbons) and some heavier organic molecules were introduced as reactive ''dopant'' flows, F d , at ‰ concentrations in the F ¼ 10 standard liters per minute (slm) flow of argon. We have earlier perfected and reported a method for measuring E g , the energy dissipated per cycle of the applied a.c. voltage, and DE g , the energy difference with and without reactive dopant in the Ar flow. The latter and F d permit calculation of E m , the energy absorbed from the plasma by each dopant molecule. Plots of E m versus F d and 1/F d yield much valuable information about excitation, fragmentation, and polymerization in the DBD plasma environment. Optical emission (OES) and Fourier-transform infrared (FTIR) spectroscopies help to further enhance and complement interpretation of measured data.

We report experiments at atmospheric pressure (AP) using a dielectric barrier discharge (DBD) reactor designed for plasma polymerization (PP) with "monomers" at ‰ concentrations in ca.10 standard liters per minute of argon (Ar) carrier gas. We have perfected a method for measuring Eg, the energy dissipated per cycle of the applied a.c. high voltage, Va(f), but the focus here is on ΔEg, the energy difference with and without a flow, Fd, of monomer in the Ar flow, with the plasma being sustained at Va(f) = 2.8 kVrms, f = 20 kHz. From ΔEg and Fd, we derive a characteristic energy per molecule, Em (in eV), and investigate plots of Em versus Fd and 1/Fd for three model "monomers": formic, acetic, and acrylic acid. These data, along with those for lighter or heavier organic compounds, reveal novel information about energy absorption from the plasma and ensuing polymerization reactions.

No abstract

In the plasma polymerization literature, there has been an interest since at least the 1970s to correlate the structure of plasma polymer (PP) deposits with plasma parameters during deposition, most particularly with the energy input per monomer molecule, E m . In our two laboratories, we have developed methods for measuring E m (or somewhat equivalent, E a ) in low-(LP) and atmospheric-pressure (AP) discharge plasmas. In this article we propose a new parameter, the so-called energy conversion efficiency, ECE, which permits direct comparison of LP and AP experiments. This is done for the case of three model monomer compounds, ethane, acetylene, and acrylic acid (AAc). ''Critical'' energy values that demarcate ECE regimes separating different fragmentation/reaction mechanisms agree remarkably well for all three monomers examined; resulting E m (or E a ) values are correlated with specific mechanisms, and the numerical results are convincingly supported by data from the chemical literature. Figure 6. FTIR spectra of (a) LP PP-AAc, and of (b) AP PP-AAc thin film deposits. Numbers in brackets represent values of energy per monomer molecule (in eV). Also shown are spectral assignments of the various observed absorption bands. Energy Conversion Efficiency in Plasma Polymerization.

A large research reactor for dielectric barrier discharge (DBD) experiments at atmospheric pressure (AP) has been used with argon (Ar) carrier gas under constant plasma conditions (f = 20 kHz, Va(f) = 8 kVp‐p = 2.8 kVrms). Five esters, acrylates with differing number of unsaturations were used as “monomers”; monomer flows, Fd, were at ‰ concentrations in the F = 10 standard liters per minute (slm) of argon. We earlier perfected and reported a method for measuring Eg, the energy dissipated per cycle of the applied a.c. voltage, and ΔEg, the energy difference with and without monomer in the Ar flow. The latter, combined with Fd enable calculation of Em, the average energy absorbed from the plasma per monomer molecule. Plots of Em versus Fd and 1/Fd yield much valuable information, for example about the role of CC and CC bonds in fragmentation and polymerization reactions. Fourier‐transform infrared (FTIR) spectroscopy, spectroscopic ellipsometry (SE), and scanning electron microscopy (FEG‐SEM) further enhance and complement data interpretation.

The electrical discharge characteristics of a large-area experimental dielectric barrier discharge in argon-hexamethyldisiloxane mixtures containing up to about 1,600 ppm of the monomer is analysed by means of electrical measurements and numerical modelling. A time-dependent, spatially onedimensional fluid model is employed, taking into account the spatial variation of the discharge plasma between the two plane-parallel dielectrics covering the electrodes. Reasonable agreement between electrical measurements and modelling results is generally found for the gap voltages and discharge currents. Remaining differences between the measured and calculated electrical energy dissipated in the plasma per period are discussed.

We report dielectric barrier discharge (DBD)‐based atmospheric pressure (AP) plasma enhanced chemical vapor deposition (PECVD) experiments using argon carrier gas and ethyl lactate (EL) as the precursor molecule (“monomer”). As in our preceding research with other monomers, unprecedented precision and reproducibility is again demonstrated, here to create plasma polymerized (PP‐EL) deposits. PP‐EL is thought to be an excellent candidate for bio‐medical applications on account of the non‐toxic nature of resulting PP‐EL deposits. We have shown that a narrow range of energy values absorbed from the plasma, Em, between roughly 21 and 42 eV/molecule, lead to PP‐EL coatings of widely varying structural and physical properties, ones with controlled retention of chemical features of the EL monomer, and a predictable rate of degradation in aqueous media.

We report dielectric barrier discharge (DBD)‐based atmospheric pressure (AP) plasma polymerization (PP) experiments using argon carrier gas and a wide variety of hydrocarbon molecules as the precursors (“monomers”). As in our preceding research with other reagents, unprecedented precision and reproducibility in energy measurements is again demonstrated. Measurements based on various aliphatic and aromatic hydrocarbon compounds have yielded values of Em, the energy absorbed from the plasma by each monomer molecule. Systematic differences among families of compounds enabled us to draw several important conclusions about fragmentation and polymerization in the DBD plasma environment, observations which are in fair qualitative agreement with low‐pressure radio‐frequency PP data by Yasuda and Hirotsu from the 1970s.