INFRARED STUDY OF THE AMIDE GROUP ISOLATED IN AN AMORPHOUS HYDROCARBON MATRIX AT LOW-TEMPERATURE - AGGREGATION AND REARRANGEMENT UPON ANNEALING

The amide group in a number of methyl N-alkyl and C-alkyl amides has b een isolated at low temperature in a hydrocarbon environment. The infr ared spectrum of the free amide group has been measured and its charac teristic bands assigned. The amide bands for some of the hydrogen bond ed n-mers have also been characterized: The isolation was achieved by the condensation of alkyl amide vapor onto the surface of a window at 8 K. Dilution with n-alkane vapor during the deposition was employed t o increase the degree of isolation. The as-deposited films at 8 K were completely amorphous. A series of major structural changes occurred w hile the as-deposited films were annealed. These were monitored by inf rared spectroscopy. With increasing temperature, the relative concentr ations of the various n-mer species change to favor the higher n-mers. In addition, the hydrocarbon chains undergo conformational ordering, accompanied by a transformation of the amorphous solid to a crystallin e solid. The triclinic subcell of the crystal changes to orthorhombic perpendicular with increasing temperature. The onset temperature and t he chain-length dependence of the onset temperature for the various so lid-solid transformations were compared to the corresponding values re ported previously for similarly prepared amorphous films of the n-alka nes.