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

Abstract

ABSTRACT:The methodology described in the previous article was utilized to study the plasma chemistry of precursors related to methyl methacrylate (MMA). This article discusses the plasma chemistry of methyl crotonate (MC), methyl isobutyrate (MIB), ethyl methacrylate (EMA), vinyl acetate (VA), isopropanol (IA), and methanol. The monomer structure was found to have strong effects on the dissociation chemistry and product formation. For ␣,␤-unsaturated esters and VA, intramolecular rearrangement (the C-O bond cleavage reaction) and decarboxylations are two efficient dissociation pathways. The intramolecular rearrangement reaction yields a pair of ketene and aldehyde neutrals. Decarboxylations produce CO, CO 2 , and a number of radicals that subsequently stabilize to form neutrals. For example, the secondary propyl radicals generated from MMA and EMA decarboxylations form propylene and allene neutrals while the primary propyl radicals generated from MC decarboxylations form propylene and acetylene. The other monomers studied, such as MIB and IA, cannot dissociate via this intramolecular rearrangement mechanism. As a result, they decompose much slower in the plasma.

Functional Plasma Polymerized Surfaces for Biosensing

“…Nevertheless, the plasma conditions have to be carefully optimized due to reactive carboxylic groups that are lost through the CO 2 release during the deposition process . Methyl methacrylate is another widely used monomer, which also exhibits significant chemical degradation under plasma conditions. , To overcome this issue, the monomer structure has to be carefully examined prior to use. It was recently shown that the plasma polymerization of glycidyl methacrylate strongly favors a conventional pathway of the free radical polymerization process .…”