Syndiotactic polystyrene spectra

On the other hand, the spectrum of the THF-insol. (spectrum (C) of Figure 3) was quite different from that of the THF-sol. The peaks at 145.6, 45.0, and 41.6 ppm were coincident with those of syndiotactic polystyrene. These findings indicate that the copolymer obtained is a mixture of ES alternating copolymer and syndiotactic polystyrene, suggesting that the active center producing ES alternating copolymer is different from that producing syndiotactic polystyrene. 

Table 8.2 Vibrational assignments for syndiotactic polystyrene and model compounds within 600-800 cm region of Raman spectrum ...

The tacticity of anionically prepared polystyrenes has been the subject of extensive study by a number of groups of workers, mostly by means of 13C-NMR spectroscopy. From a study of the aromatic Cl resonances, Matsuzaki and coworkers found 234) that there is a tendency towards syndiotacticity when using -butyl-Iithium in toluene as initiator. From the sensitivity of the CMR spectrum to the nature of the solvent employed it was concluded that the polymerization did not conform to Bernoullian statistics. Randall examined the methylene resonances in the CMR spectrum and concluded that butyllithium initiated polystyrene is essentially atactic 235) and that propagation is Bernouillian. Uryu et al.236) examined polystyrene... 

Figure 9.36 Raman spectra of polybutadiene-polystyrene copolymer in the C=Cstretching region showing three distinct bands of polybutadiene isomers cis-1,4 at 1650 cm-1, trans-1,4 at 1665 cm-1 and syndiotactic-1,2 at 1655 cm-1 (a) spectrum from the center of sample and (b) spectrum from the edge of sample. (Reproduced with permission from G. Turrell and J. Corset, Raman Microscopy, Developments and Applications, Academic Press, Harcourt Brace Company, London. 1996 Elsevier B.V.)...

Stereoregularity We have already discussed the stereoregularity of the IR spectrum of polystyrene. Figure 17.23 shows three IR spectra of polypropene. The spectra of atactic, syndiotactic, and isotactic polypropene are virtually the same at wave numbers of 1000cm and above. Remarkable spectral differences are observed, however, in the spectra at wave numbers below 1000 cm . This is consistent with our observations on the IR spectra of atactic, syndiotactic, and isotactic polystyrene as mentioned previously. 

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