Polystyrene solution transient absorption spectrum

Figure 8. Transient absorption spectrum obtained by pulse radiolysis of 200 mM polystyrene solution in cyclohexane.

The transient absorption spectrum obtained in the pulse radiolysis of polystyrene solution in CC1 is shown in Figure 13. The spectrum is very similar to the charge transfer radical complex (PS4+C14-) species. The lifetime is about 200 ns. Consideration of the absorption spectrum and the lifetime suggest that this species is (PS4+C14-)-. The processes leading to formation of this species in liquid CC14 can be written as follows (4,7). 

Reaction Scheme of CMS Resists. The transient absorption spectrum shown in Figure 6 and observed for irradiated CMS films is mainly composed of two components as based on pulse radiolysis data of solid films of CMS and polystyrene, and CMS and polystyrene solutions in cyclohexane, chloroform, and carbon tetrachloride. An absorption with a maxima at 320 nm and 500 nm as due to the charge transfer radical-complex of the phenyl ring of CMS and chlorine atom (see Figure 14) and an absorption with maxima at 312 and 324 nm is due to benzyl type radicals (see Figure 11). 

Fig. 1 shows the transient absorption spectra observed during photolysis of cyclohexane solutions of CMS. The absorption spectrum with the peak at 520 nm (spectrum a) is identical to that of the excimer of polystyrene (spectrum C) (22) and has a similar lifetime of 20 ns. The quenching rate of the absorption at 520 nm by O2 is comparable to what one would expect for the CMS excimer. 

On the basis of these results we consider that transient absorption spectral measurements of solids are possible with the two-photon excitation method. Here our recent experimental demonstration of two typical polymer systems is presented in order to confirm our idea. One example is the ps 355 nm photolysis of a polystyrene plate with a thickness of 1 mm (40). As in the case of benzenes, solid polystyrene gave an excimer absorption band whose peak position was the same as those of liquid toluene and cumene. Another system we examined is a very viscous, glass-like solution of poly(N-vinylcarbazole) in THF. This sample was used instead of a block of a solid polymer because the latter was very diffucult to prepare. The ps 532 nm photolysis of this sample gave the absorption spectrum shown in Fig.10... 

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