A polyamide imide and a polymeric precursor to polyimide have both been successfully transferred using resonant
infrared laser ablation. Additionally a random copolymer mixture, possessing structural features common to polyimide
and polyamide imide, was readily transferred using resonant infrared laser ablation. The materials are transferred with
local structure intact as evidenced by Fourier transform infrared spectroscopy studies. The deposition rates of the
polyimide precursor were examined at various wavelengths using a quartz crystal microbalance mounted in the
deposition chamber. The effect of target type on deposition rate was also examined using two different 20 wt%
polyamide imide solutions in N-methyl pyrrolidinone and dimethyl formamide and a solid pressed pellet target of
polyamide imide. Both wavelength and target form were found to have a discernible effect on deposition rate. The
deposited material was examined using a combination of profilometry and optical microscopy. The results show highly
rough films with large, dark, string-like polymeric moieties on the surface.
Experiments on pulsed laser vaporization of many different kinds of polymers have demonstrated that it is possible to
eject intact polymers into the ambient, whether air or vacuum, by resonant pulsed laser excitation, using both neat and
matrix targets. Two recent studies of resonant infrared ablation - one on polystyrene, the other on poly(amic acid), the
precursor for the thermoset polyimide - show moreover that the ablation process is both wavelength selective and
surprisingly non-energetic, especially compared to ultraviolet laser ablation. We propose a wavelength-selective photothermal
mechanism involving breaking of intermolecular hydrogen bonds that is consistent with these observations.
Poly(amic acid) (PAA), a precursor to polyimide, was successfully deposited on substrates without reaching curing temperature, by resonant infrared pulsed laser ablation. The PAA was prepared by dissolving pyromellitic dianhydride and 4, 4' oxidianiline in the polar solvent N-methyl pyrrolidinone (NMP). RIR-PLD transferred material showed two distinct geometries, droplets and string-like moieties. The unaltered nature of the deposited PAA was confirmed by Fourier transform infrared spectroscopy (FTIR). Thermal curing was achieved by heating for one hour on a 250°C hotplate, and the transformation to polyimide was demonstrated from changes in the FTIR spectrum following curing. Plume shadowgraphy showed very clear contrasts in the ablation mechanism between ablation of the solvent alone and the ablation of the PAA, with additional contrast shown between the various resonant frequencies used.