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The infrared absorption of trifluoroacetic acid vapor in the region between 2 and 24 μ has been studied as a function of temperature. At room temperature both monomer and dimer molecules are present, while at 100°C the vapor is predominantly monomeric. On the basis of the resulting intensity changes it has been possible to conclusively identify the bands due to the two species. A partial assignment of the fundamental modes of vibration has been made using these data and the previously published spectrum of the deuterated acid. The heat of dissociation (ΔH) for the dimer-monomer reaction has been determined from the temperature dependence of the OH stretching bands and found to be 13.7±0.4 kcal/mole.

Thin films of poly(methyl acrylate) at room temperature have been photodegraded in air and in vacuum by radiation from a low‐pressure mercury source. Changes in intrinsic viscosities, ultraviolet absorption, and volatile products were followed as a function of the energy absorbed. Crosslinking occurs in both air and vacuum, but at a slower rate in air. The apparent quantum yield for random scission in air was 0.013 scissions per quantum absorbed. In air, carbonyl groups are formed along the backbone chain. Most of the volatile products studied appear to orginate from the ester groups in the polymer; formaldehyde, methanol, and methyl formate evolved at a constant rate for doses up to at least 2 × 1020 quanta/g.; quantum yields for each were determined. Carbon dioxide forms in amounts increasing exponentially with dose. Small amounts of carbon monoxide, methane, and hydrogen were detected qualitatively, but monomer was not observed. A mechanism compatible with these findings is suggested.

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