Spectra polyacrylonitrile

The initial radicals formed from the Ce(IV) ion redox system can initiate a monomer to polymerize and form an end group of the resulting polymer. When the reductant exhibits a carbonyl group, the amide group can be conveniently detected by the FT-IR spectrum of the polymer, such as polyacrylonitrile (PAN). The FT-... 

Exceptions do exist as shown in the spectrum of polyacrylonitrile in Figure 6. The methine resonances show a distinct triplet with very little splitting exhibited by the methylene resonances. The greatest sensitivity toward configuration occurs for the nitrile resonances where an almost ideal Bemoulllan distribution is observed. ... 

Figure 4 shows the off-resonance proton decoupled C NMR spectrum of the cellulose acetate-polyacrylonitrile graft polymer. The spectrum of the graft polymer showed a) the carbonyl carbon of the acetate at 172 ppm, b) the nitrile carbon at 120, c) the carbon of the sugar at 101 ppm, d) the C2 -carbons of the sugar between 60-80 ppm, and e) the aliphatic carbons in the 10-20 ppm region. 

The formation of rings in the pdymer chain by the pdymerization of nitrile groups has also been observed in the bulk pd3rmerization of acrylonitrile by Trifonov and Shopov. In this study of the electroinitiated pdymerization of acrylonitrile with tetraethylammonium perchlorate as supporting electrolyte, the polymer was formed on a germanium prism which was part of an internal reflection spectroscopy device. The appearance of the absorption band at 1570 cm" in the spectrum of Ae yellow colored polymer indicated the presence of conjugated multiple bonds idiich was also supported by uv absorption at a lot r wavelength 304 tun, compared to 271 nm for white polyacrylonitrile prepared by free-radical initiation. 

Infrared spectra of the zeolite/polymer inclusions and of PAN extracted from the zeolites show also peaks characteristic of the bulk polymer,including methylenic C-H stretching vibrations of the backbone (2940 cm l and at 2869 cm"l), and a band at 2240 cm l due to the pendant nitrile group. The spectra of the extracted intrazeolite polymers are indistinguishable from the spectrum of the bulk polymer. We conclude that the polymer formed in the zeolites is polyacrylonitrile. 

The most important band in the spectrum is the 2248 cm band that is assigned to the unconjugated nitrile stretch. The most likely simple polymer containing a nitrile group is polyacrylonitrile, and by referring to reference spectra, this identification is confirmed. The bands at 3632 and 3539 cm may present some confusion unless it is known that this polymer was prepared by an emulsion polymerization process. The assignment of these bands is to the presence of some residual water and a trace of an antioxidant. The answer is polyacrylonitrile. 

FIGURE 26.19 IR spectrum of an acrylic fiber. Note the CN triple-bond absorption at 2243 cm- and the carbonyl absorption at 1733 cm-. If you recall the chapter on polymers, pure polyacrylonitrile is very difficult to process, and usable fibers usually contain other acrylic materials, including esters and amides. Like most fibers, this absorbs some moisture from the atmosphere, so an OH as well as an NH peak is also observed. 

---