Search

The method we have developed for understanding energetic exchanges between precursor molecules and argon (Ar) carrier gas in a dielectric barrier discharge (DBD) has much‐proven merit. The present article focuses on hydrofluoromethanes, CHxFy. The precursors (‰ concentrations) were mixed with Ar in a 20 kHz, 8 kV (peak‐to‐peak) DBD. For each compound, Em, the energy absorbed per molecule, was plotted as a function of precursor flow rate. Besides the determination of Em, we have used optical emission spectroscopy as a diagnostic of the plasma physicochemistry. The influence of chemical structure has been investigated by depositing thin plasma polymer coatings; we have measured their deposition rates and water contact angles, which have been correlated with Em values and X‐ray photoelectron spectroscopy measurements. [ABSTRACT FROM AUTHOR]

We have studied “PEG‐like” plasma‐deposited coatings of poly(ethylene glycol), some of which prevent protein adsorption and cellular adhesion. This enables inhibition of possible inflammatory reactions or rejection of an implant following its insertion into living tissue. Our approach, based on electrical measurements in atmospheric pressure Ar dielectric barrier discharges, enables precise measurements of E m, the energy absorbed per monomer molecule. Here, we demonstrate the importance of E m in preparing PEG‐like coatings for biomedical applications, for example by highlighting the great importance of molecular weight of monoglyme (1G) or diglyme (2G) monomers, and by obtaining anti‐fouling layers, “PP‐2G,” only with the diglyme. We demonstrate resistance to protein adsorption and cell adhesion of PP‐2G surfaces prepared with optimized F d (and E m) values. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 Δ Eg, 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. [ABSTRACT FROM AUTHOR]

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 = 20 kHz, Va( f) = 8 kVp-p = 2.8 kVrms). Various permanent gases (H2, O2, N2, light hydrocarbons) and some heavier organic molecules were introduced as reactive 'dopant' flows, Fd, at ‰ concentrations in the F = 10 standard liters per minute (slm) flow of argon. We have earlier perfected and reported a method for measuring Eg, the energy dissipated per cycle of the applied a.c. voltage, and Δ Eg, the energy difference with and without reactive dopant in the Ar flow. The latter and Fd permit calculation of Em, the energy absorbed from the plasma by each dopant molecule. Plots of Em versus Fd and 1/ Fd 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. [ABSTRACT FROM AUTHOR]

The method developed for fundamental understanding of energetic exchanges between monomer molecules and argon carrier gas in a dielectric barrier discharge (DBD) has previously proven merit. In this seventh article related to this methodology, research has been extended to a new family of precursors: anhydrides. Monomers (typically ‰) were mixed with 10 slm of Ar in a 20 kHz, 8 kV (peak‐to‐peak) DBD corresponding to an energy per cycle of 1600 μJ for pure Ar. For each of the investigated monomers Em, the energy absorbed per molecule was plotted as a function of precursor flow rate. The influence of chemical structure (C/O ratio, unsaturation) has been investigated and compared with previous data for other types of precursors. Thin plasma polymer coatings were deposited; in addition to measuring deposition rates, we also present relationships between Em values, spectro‐ellipsometric and FTIR measurements. [ABSTRACT FROM AUTHOR]