Temporal evolution of an electron-free afterglow in the pulsed plasma polymerisation of acrylic acid.

By use of time and energy-resolved mass spectrometry, negative ions with masses ranging from m/z = 1-287 amu have been observed in the afterglow of a low-pressure (10 mTorr) pulsed acrylic acid polymerizing plasma. The most intense peaks, seen at m/z = 71, 143, 215, and 287, are assigned to the dehydrogenated oligomer of the form [nM-H](-) for n = 1, 2, 3, and 4, respectively. The results strongly suggest that both m/z = 71 and 143 ions are produced in the on period of the pulse cycle (0.

Detection of negative molecular ions in acrylic acid plasma: some implications for polymerization mechanisms.

There is much scientific and commercial interest in plasma polymers to modify surface chemistry. To date, only neutral and positively charged species have been detected in the commonly applied acrylic acid plasma. Using time-averaged negative ion mass spectrometry, we demonstrate that large, negatively charged species exist in the plasma, contrary to previous studies that detected only neutral and positive species.