Quench method, isopentane

After observation, this film was placed in a vacuum oven at 100° C for 10 hr. This sample history will be referred to as annealed. An additional sample was quenched and subsequently was annealed by the same method, but using ice water as the quenching medium. Although this sample was not studied cryogenically with IR, it allowed a comparison with the isopentane quenching method. 

When the isopentane-quenched sample is annealed at 100 °C for 10 hr, only a 10% decrease in amorphous structures is observed (Figure 12). The crystalline vibrations show only a slight increase. The difference spectra at 78 K show the same behavior (Figure 13). A sample was also quenched in ice water for comparison with the isopentane quench method. The subtractions of the spectra of the two quenched specimens from the low-crystallized one are shown in Figure 14. Each technique produces a similar amount of amorphous conformations. The decreases in amorphous content by annealing are the same for both systems (Figure 15). 

The method of digitally subtracting spectra is illustrated in Figure 10. This subtraction shows that the isopentane-quenched sample has twice as much amorphous material as the one which was slow-crystallized. The expansion factor for plotting of the difiFerence spectrum rela-... 

Additional information is available by subtracting spectra taken at different temperatures for the same sample. Since the position of the film was not altered as the temperatures varied, a 1 1 subtraction is a systematic method to illustrate the thermal eflFects. The spectra at the two temperature extremes for a slow-crystallized sample are subtracted in Figure 20. The 909 and 990 cm vinyl bands narrow in width, increase in intensity, and shift to slightly higher frequency as the temperature is decreased. The crystalline absorptions at 1050 and 1176 cm shift to lower frequency and sharpen considerably. The 1303 cm amorphous absorption shifts its maximum to 1300 cm and possibly increases in intensity. The 1353 cm" band remains fixed in position. The most intense amorphous band, 1369 cmmoves to 1371 cm at 78 K and has an intensity increase. These results are shown clearly in the difference spectrum. Similar results are obtained for the isopentane-quenched sample before and after annealing. 

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