Atmospheric-Pressure Plasma Polymerization of Acrylic Acid: Gas-Phase Ion Chemistry

To improve understanding of atmospheric-pressure plasma polymerization processes, the gas-phase ion chemistry of acrylic acid produced in a microsecond pulsed atmospheric pressure plasma jet has been studied using ambient mass spectrometry. Acrylic acid monomer was introduced into the helium feed prior to entry into the active discharge region and the pulse duty cycle was varied from 10-90% for frequencies of 5 and 10kHz. The ionic mass spectra show a rich variety of species up to 450Da with prominent peaks at masses corresponding to both positive and negative oligomer ions, [nM+H](+) and [nM-H](-), with up to n=6 for positive ions and n=4 for negative ions. Through variation of the pulse voltage parameters, the mass distribution of the oligomer ions produced in the outflow can be manipulated.