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Proceedings Paper

Fourier Transform Infrared (FTIR) Kinetics Diagnostics Of Thin Film Polymerization Photoinitiated By Excimer Laser Pulses
Author(s): David Klick; M Alfred Akerman; George L Paul; Darko Supurovic; Haruki Tsuda
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Paper 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.

Paper Details

Date Published: 15 August 1989
PDF: 10 pages
Proc. SPIE 1056, Photochemistry in Thin Films, (15 August 1989); doi: 10.1117/12.951616
Show Author Affiliations
David Klick, Massachusetts Institute of Technology (United States)
M Alfred Akerman, OAK Ridge National Laboratory (United States)
George L Paul, University of New South Wales (Australia)
Darko Supurovic, University of New South Wales (Australia)
Haruki Tsuda, Macquarie University (Australia)

Published in SPIE Proceedings Vol. 1056:
Photochemistry in Thin Films
Thomas F. George, Editor(s)

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