Plasma dissociation reaction kinetics. I. Methyl methacrylate

Abstract

Fourier transform infrared spectroscopy (FTIR) was utilized to study the plasma gas-phase reaction kinetics and reaction mechanisms in capacitively coupled glow discharges of methyl methacrylate (MMA) under zero monomer flow rate conditions. The gas-phase study shows two major electron-impact-induced dissociation pathways in MMA plasmas: the C-O bond cleavage reaction and decarboxylations. The C-O bond cleavage reaction accounts for approximately one-half of the MMA dissociation, and neutral formaldehyde and dimethyl ketene (DMK) are produced via intramolecular rearrangement. Decarboxylations produce CO, CO 2 , and a number of radicals that subsequently stabilize to form neutrals, including propylene, allene, and methanol. These intermediate species then further dissociate in the plasma to small hydrocarbons (methane, acetylene, and ethylene), CO, CO 2 , and H 2 . Plasma power and initial monomer pressure have only minor effects on the MMA fragmentation chemistry. However, the reaction rate increases at higher-power and lower initial monomer pressure conditions. The modeling also reveals the relative reactivities of the neutrals. A time-scale transformation technique based on the MMA decomposition half-life significantly reduces the effects of the reactor condition on the kinetics. In addition, mass balance ratios are utilized to calculate the portion of plasma species that have been accounted for by the in situ technique.

Effect of Substrate Temperature on Thermal Properties and Deposition Kinetics of Atmospheric Plasma Deposited Methyl(methacrylate) Films

“…Moreover, systematic research on the deposition kinetics and thermal properties of plasma deposited films at atmospheric pressure as a function of T substrate is completely lacking. In this work, MMA is selected as a precursor because in literature, extensive efforts have been put in the chemical characterization of pdMMA thin films produced at atmospheric pressure . Differential scanning calorimetry is used in this work to quantify the thermal properties of pdMMA films, systematically measured as‐deposited, and produced in a DBD reactor operating at atmospheric pressure.…”

Novel Polymeric Thin Films from Labile Lactic Acid by a Dry Process

“…Specific to the decease of oxygen‐containing functionalities associated with increased plasma powers, a corresponding increase of CO emission in OES spectra (as shown later in Figure 11a) were detected in the LLA plasma vapor phase. This indicates that, under high‐energy conditions, the carbonyl‐containing fragments tend to convert to gaseous CO or CO 2 molecules and escape to result in the oxygen deficiency in the film 36, 37. Moreover, the strong signal at 127 ppm indicates that formation of C=C bonds can arise from both bond‐rupture reaction routes and UV‐induced Norrish type II reactions, as will be discussed more in detail later.…”

Plasma dissociation reaction kinetics. II. Precursors related to methyl methacrylate: Methyl crotonate, methyl isobutyrate, ethyl methacrylate, and vinyl acetate

“…Closed (zero flow rate) MC plasmas were studied in a 2 2 full factorial designed experiment with the same pressure and power settings as those of the closed MMA plasma kinetics study ( pressure levels: 300 and 500 mT; power levels: 75 and 100 W) 2 . In situ FTIR was utilized to provide gas‐phase information at different plasma reaction times.…”

“…The same experimental setup and procedures from the previous article2 (“Plasma Dissociation Reaction Kinetics. I.…”

“…Alkyl ketene ions were found in the electron‐impact ionization of a number of α , β ‐unsaturated esters other than MMA 1. Thus, the plasma dissociation mechanisms of MMA2–5 may have applications toward other α , β ‐unsaturated esters, such as MC and EMA.…”