Fourier Transform Infrared (FTIR) Kinetics Diagnostics Of Thin Film Polymerization Photoinitiated By Excimer Laser Pulses

David Klick; M Alfred Akerman; George L Paul; Darko Supurovic; Haruki Tsuda

doi:10.1117/12.951616

15 August 1989 Fourier Transform Infrared (FTIR) Kinetics Diagnostics Of Thin Film Polymerization Photoinitiated By Excimer Laser Pulses

David Klick, M Alfred Akerman, George L Paul, Darko Supurovic, Haruki Tsuda

Author Affiliations +

Proceedings Volume 1056, Photochemistry in Thin Films; (1989) https://doi.org/10.1117/12.951616
Event: OE/LASE '89, 1989, Los Angeles, CA, United States

Abstract

Rapid-scan Fourier transform infrared (FTIR) spectroscopy is becoming a useful method for monitoring reaction kinetics. The excimer laser has recently appeared as a source of intense UV radiation for laser-assisted photochemistry. These two tools are combined in this study of the polymerization rates of commercially useful transparent thin films. Liquid mixtures made up of 3 parts epoxy oligomer and 2 parts di- or tri-acrylate monomer, with 3-5% of various photoinitiators and 3% amine, were spread on NaCl plates in 7 μm layers. Transmission FTIR spectra were taken with the sample in an N2 atmosphere. Excimer laser pulses at either 308 or 351 nm and spanning a range of fluences from 10 -4 to 10 -2 J/cm 2 (below the damage level) illuminated the sample. The photoinitiator absorbed the UV light and initiated a chain reaction that led to full polymerization of the coating. FTIR scans of 4 cm -1 resolution were taken every 80 msec during the reaction. Extent of reaction was monitored by the disappearance of the acrylate C=C bond at 810 cm -1, with reference to the unchanging peak at 830 cm -1. Typical experiments at high fluence involved a pulse or fast series of pulses (sufficient to lead to complete polymerization) followed by rapid FTIR scanning as the reaction proceeded. At low fluence, many series of pulses were required to complete the reaction, and each series was followed by an FTIR scan. Kinetics data were taken with several fluences, wavelengths, and sample compositions. These and other simpler kinetics diagnostics measurements are discussed in the context of a search for an industrially useful laser-cured polymer coating process.

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David Klick, M Alfred Akerman, George L Paul, Darko Supurovic, and Haruki Tsuda "Fourier Transform Infrared (FTIR) Kinetics Diagnostics Of Thin Film Polymerization Photoinitiated By Excimer Laser Pulses", Proc. SPIE 1056, Photochemistry in Thin Films, (15 August 1989); https://doi.org/10.1117/12.951616

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