Infrared spectra polystyrene

In some cases crystalline polymers show additional absorption bands in the infrared spectrum, as in polyethylene ( crystalline band at 730 cm amorphous band at 1300 cm" ) and polystyrene (bands at 982,1318, and 1368 cm" ). By determining the intensity of these bands it is possible to follow in a simple way the changes of degree of crystallinity caused, for example, by heating or by changes in the conditions of preparation. 

TITLE=polystyrene (film 38.lMm) JCAMP-DX=4.24 Nicolet v. 1 DATATYPE=INFRARED SPECTRUM ORIGIN= OWNER=IUT Le Mans DATE=1999/12/16 TIME=13 09 20 DATA PROCESSING=Ratio against background XUNITS=1/CM YUNITS=TRANSMITTANCE... 

Figure 20-29 Fourier transform infrared spectrum of polystyrene film. The Fourier transform of the background interferogram gives a spectrum determined by the source intensity, beamsplitter efficiency, detector response, and absorption by traces of H20 and C02 in the atmosphere. The sample compartment is purged with dry N2 to reduce the levels of H20 and C02. The transform of the sample interferogram is a measure of all the instrumental factors, plus absorption by the sample. The transmission spectrum is obtained by dividing the sample transform by the background transform.

The infrared spectrum of a sample of atactic polystyrene is shown in Fig. 15 [Liang and Krimm (114)]. The band positions are given in Table 16, on the left-hand side of the "Infrared column. Raman data for atactic polystyrene [Signer and Weiler (198) Palm (163)] are also included in the table. Polarized spectra of oriented specimens of isotactic polystyrene have recently been published [Tadokoro, Nishiyama, Noza-kura, and Murahashi (227) Tadokoro, Nozakura, Kitazawa, Yasuhara, and Murahashi (222) Takeda, Iimura, Ya-mada, and Imamura (222a) Morero, Man-tica, Ciampelli, and Sianesi (140a)]. The spectrum of the isotactic polymer differs slightly from that of the atactic polymer, and these differences (above 500 cm-1) are shown... 

Although some aspects of the proposed assignments will require additional confirmation in order to be more certain that they are correct, it appears at present that the basic framework of a set of assignments for isotactic polystyrene exists. These assignments enable the use of the infrared spectrum of an oriented... 

The infrared spectrum of the precipitated polystyrene at this stage exhibited no absorption using thermally polymerized polystyrene in the reference beam. A 3.5% solution of dried Triton X-405 in chloroform showed intense adsorption at about 1100 cm. 1, characteristic of the ether linkage. 

The infrared spectrum (KBr disks) was recorded on a Perkin-Elmer 683 spectrometer (range 4000-200 cm 1, calibrated with polystyrene lines) and was found to be superimposable on that given in Ref. 26. This spectrum was used by Becke-Goehring and Boppel as evidence for the ANSA structure. It is demonstrated below how careful one has to be when assigning a certain molecular configuration on the bases of indirect structural techniques such as IR spectroscopy. 

Run the infrared spectrum of an unknown carbonyl compound obtained from the laboratory instructor. Be particularly careful that all apparatus and solvents are completely free of water, which will damage the sodium chloride cell plates. The spectrum can be calibrated by positioning the spectrometer pen at a wavelength of about 6.2 p without disturbing the paper, and rerunning the spectrum in the region from 6.2 to 6.4 p while holding the polystyrene calibration film in the sample beam. This will superimpose a sharp calibration peak at 6.246 p (1601 cm ) and a less intense peak at 6.317 p (1583 cm ) on the spectrum. Determine the frequency of the carbonyl peak and list the possible types of compounds that could correspond to this frequency (Table 2). 

It is good practice to check the accuracy of infrared spectrophotometers (including FT-IR spectrophotometers) at regular intervals by reference to the infrared spectrum of a standard. Conventionally polystyrene has been employed for the purpose (the bands at 1603 and 1028 cm being particularly useful). The frequency accuracy of a modem instrument is normally internally cahbrated automatically by the instrument. 

The infrared spectrum of the polystyrene sample investigated (Figure 1) was equivalent to that of published standards (33). 

The infrared spectrum of the SMA coplymer specimen exposed to hydrochloric acid is shown as Figure 8. The shifts in absorptions in the range of 665-910 cm l are again toward lower frequencies as are seen in the spectrum of polystyrene (Figure 7). The peaks at 1447 cm , 1496 cm l, 1601 cm and 1780 cm"l (Figure 3) are essentially unchanged by exposure to concentrated hydrochloric acid at 25°C wherein absorptions at 1452 cm , 1494 cm l, 1601 cm 1 and 1778 cm" are observed. Therefore, it was concluded that the SMA did not exhibit a significant increase in reactivity toward hydrochloric acid. 

The polystyrene specimen exposed to glacial acetic acid was removed from a bO C oven and the solution was quenched in an effort to slow diffusion of acetic acid out of the sample (Figure 10). The specimen was approximately 25% of its previous size and was severely crazed. The infrared spectrum shows the presence of acetic acid approximately three days after removal and cleaning. The absorption peaks at 1030" , 1050" , 1260"l, 1310 , 1420 l and at approximately 1735 cm l are indicative... 

Liang and Krimm(16) discussed the infrared spectrum of polystyrene, summarizing the frequency, relative intensity and origin of each... 

Determine the identity of the samples (probably either polyethylene or polystyrene) by comparing your unknown spectra to the known spectra that have been collected. Look for patterns in the unknown spectra that don t match up with the patterns in the known spectra. This would indicate a foreign material or a material other than polyethylene or polystyrene. If the spectra don t match up with those of polyethylene or polystyrene, attempt to identify the film or the nature of the foreign material based on your knowledge of infrared spectrum interpretation protocols. 

Figure 10.2 Mid-IR spectrum of a polystyrene film. The typical representation of an infrared spectrum with a linear scale abscissa in cm (see formula 10.1) for an easier observation of the right-hand section and with percentage transmittance along the ordinate. The transmittance is sometimes replaced by the absorbance A(A = — log T). The scale, in cm , (or kaysers) is linear in energy E = hc/X) and will decrease from left to right (i.e. from high to low energy).

The fields have advanced way beyond the simple determination of spectra and correlating particular bands with particular chemical groups. Today, specific motions are calculated. For an example, see Figure 2.1 (4). Here, two conformational displacements of polystyrene are shown—one near 550 cm" in the infrared spectrum, and one near 225 cm in the Raman spectrum. These motions illustrate a degree of coupling between the ring and backbone vibrations. 

Figure 7.11 The infrared spectrum of polystyrene shown in a 2D presentation. For details see text. Diagram due to Noda et al. [17]...

Albert [119] has compared determinations of butadiene in high-impact polystyrene (HIPS) by an infrared method and by the iodine monochloride method described by Crompton and Reid [113]. The infrared method is based on a characteristic absorbance in the infrared spectrum associated with the transconfiguration in polybutadiene ... 

These days, with modem instrumentation being so good, is not so essential to check the wavelength calibration of the spectrometer before running an infrared spectrum. This checking of the calibration may be done by examining a suitable reference substance (such as polystyrene film, ammonia gas, carbon dioxide gas, water vapour or indene) which has sharp bands, the positions of which are accurately known in the region of interest. 

FIGURE 1.2 The infrared spectrum of polystyrene. Note that the x-axis is plotted in wave-number and that the y-axis is in absorbance. 

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