Polarized infrared spectrum

Figure 5 Polarized infrared spectra (s on top, p on bottom) recorded for an oriented 80/20 PS/PPO miscible blend using normal incidence transmission. Reproduced with permission from Lefebvre et al. [23]. Copyright Elsevier 1981.

The polarized infrared spectra of crystalline q3-C3HsFe(CO)2(NO) and n3C3H5Co(CO)3... 

Spectra. Infrared, Raman, and NMR spectra of PTHF have been reported. Imada et al. (84) have reported the Raman and polarized infrared spectra (Fig. 33). They made a tentative assignment of the bands. 

Fig. 33. (a) Raman spectrum and (b) polarized infrared spectra of PTHF. The solid (or broken) line in (b) represents the spectrum measured with the electric vector perpendicular (or parallel) to the orientation... 

Polarized infrared spectra of oriented specimens of isotactic polypropylene are shown in Fig. 14 [Peraldo (167)]. The band positions, polarizations, and relative intensities are given in Table 14, together with Raman data [Tobin 231)] and information on the phase of origin of the bands [Natta [149) Pokrovsky and Volken-shtein 178) Abe and Yanagisawa (/)]. Some preliminary data on partially deuterated polypropylenes are available [Peraldo 167) Natta 130)], but no detailed spectra have as yet been published. 

Figure 9 shows the change of the polarized infrared spectra by adsorption of diethyl ketone. Several bands appear by crystallization especially at 858 cm-. The bands due to diethyl ketone itself are not observed. The essential features of the x-ray diagrams and infrared spectra are the same irrespective of the kinds of solvents. From these results it may be considered that formation of a complex of syndiotactic PMMA and solvent molecules is not reasonable, and the adsorbed molecules contribute to the stabilization of crystallites of syndiotactic PMMA. 

Furthermore, the conformation and orientation of the hydrocarbon chains of MS in the MS-C20 binary and MS-C2o-AL18 ternary systems were investigated by using infrared absorption spectroscopy. In this respect, deuterated arachidic acid (C2o-d) and deuterated n-octadecane AL %-d) were utilized to separate infrared bands due to the hydrocarbon chains of MS from those arising from C2o and AL18. Fig. 26 shows polarized infrared spectra A of 10-layer LB films of pure cadmium arachidate (CdC20), MS-C20- binary and MS-C20-t/-AL18-t/... 

Fig. 28. (a) Surface pressure (rc) area (A) isotherms of mixed monolayers of the MS-C2o binary and MS-C20-AL18 ternary systems with the molar mixing ratios of [MS] [C2o] [ALi8] = 1 2 x (x — 0 and 1.0) on a subphase with Cd2+ ions. (Reproduced with permission from Ref. [78]. Copyright (1999) The Japan Society of Applied Physics.) (b) Polarized infrared spectra Ay of LB films of CdC20-d, MS-C2o binary and MS-C2o-AL18-J ternary systems with the molar mixing ratios of [MS] [C20] [AL... 

Figure 4.7-3 Polarized infrared spectra of salmon sperm DNA films. Top 98% RH. B form bottom 58% RH, A form. Electric field of incident radiation directed perpendicularly (full line) or parallelly (dotted line) to the preferential orientation of the sample.

This technique was employed to monitor the B —> A transition of DNA as a function of the relative humidity (Pilet and Brahms, 1973 Pohle et al., 1984). The investigated bands are those which reflect the vibrations of the phosphate groups. As shown by Fig. 4.7-3, which presents the polarized infrared spectra of a salmon sperm DNA hydrated film with 93% RH (top, B form) and 58% RH (bottom, A form), the dichroism of the two phosphate bands changes. The B form of the antisymmetric PO2 stretching vibration around 1230 cm is non-dichroic, while that of the A form is perpendicular. The B form of the symmetric PO2 stretching vibration around 1090 cm is perpendicular, while that of the A form is parallel. A simple computation, for instance for the latter band, shows that the value of the angle between the transition dipole moment of this vibration and the double helical axis varies between 68 ° (B form) and 49 ° (A form). This parameter is an extremely sensitive indicator of a B A transition and may also be employed to show the inhibition of a B —> A transition by various classes of molecules, such as proteins (Liquier et al., 1977 Taillandier et al., 1979) or drugs (Fritzsche and Rupprecht, 1990). 

Raman data are beginning to appear more frequently (see for example 1, 3, 4, 8, 9, 12, 14, 16, 17, 18, 26) thus making assignments much more convincing. The value of polarized infrared spectra has been long realized but only recently (7) has the first example of the polarized infrared spectrum of a carbonyl complex appeared Mn2(CO)io and Re2(CO)io were studied in a nematic liquid crystal. The value of Cotton-Kraihanzel force constants has been further discussed (10,15) and a reasonably complete assignment of the vibrational spectrum of the cation Re(CO)e has been published (1). A number of isotopically substituted species have been studied (5, 6, 16, 23, 25). As a result of one of these studies Bor (5) reassigned the spectrum of Mn2(CO)io. 

Neither of the two earlier reviews on the infrared spectroscopy of carbohydrates " dealt with the uses of plane-polarized radiation. This is, no doubt, attributable to the fact that both reviews were principally concerned with crystalline sugars, for which few such spectra are available. However, the polarized infrared spectra of such polysaccharides as cellulose, chitin, and xylans, in the form of oriented films, have been measured " and have provided information that other techniques could not give. It is, therefore, desirable that a brief discussion should be here provided of both the experimental and the interpretational aspects (see p. 28) for a detailed discussion, the reader is referred elsewhere. The commonest method of obtaining polarized infrared radiation is with a transmission polarizer (rather than a reflection polarizer). Selenium film and silver chloride sheet have both been used of these, the latter is the more popular because it is the more robust. A stack of about six sheets, each about 50-100 m thick, is... 

The above description serves to give an idea of the basic measurements that are involved in this technique and the nature of the information that can be obtained. It leaves out many complicating factors that, in practice, have to be considered in the interpretation - of polarized infrared spectra, and it is to be emphasized that considerable caution is necessary in the use of this technique. 

Polarized Raman spectra provide more information about the symmetry properties of normal vibrations than do polarized infrared spectra [143]. Again consider a single... 

Figure 6. Percent transmission (r)-vs.-frequency traces (a) of the polarized infrared spectra of single-crystal ot-PbNg in the symmetric stretching mode region, at 90 K. The dotted curve indicates polarization parallel to the a axis and the solid-line curve indicates polarization parallel to the c axis (b) Raman Spectrum of a-Pb(N3)2 in the v region.

As is shown in Table III-26, normal coordinate analysis predicts that the highest-frequency CO stretching band belongs to the species in the unidentate and the A, species in the bidentate complex. Elliott and Hathaway studied the polarized infrared spectra of single crystals of [Co(NHj)4C03]Br and confirmed these symmetry properties. As will be shown later for nitrafo complexes, Raman polarization studies are also useful for this purpose. 

Bradbury et al. (1961) have described in detail the experimental techniques used in a study of films of DNA polymers and have recorded polarized infrared spectra of oriented sheets of the sodium and lithium salts of DNA, in both undeuterated and deuterated states, over a range of humidities between 0 and 94% relative humidity (r.h.). They found two forms of sodium DNA, one at humidities greater than 90% r.h. where the bases are perpendicular to the helix axis (B-form) and the other at humidities between 70 and 80% r.h. where the bases have tilted by an angle not less than 13° to the normal to the helix axis (A-form). Lithium DNA exists in the B-form for humidities greater than 66 % r.h., and in a second form, different from the A-form of sodium DNA, between 44 and 56% r.h. where the bases are tilted by about 4° from the perpendicular (C-form). These workers have discussed the orientation of the phosphate groups, which they inferred from dichroic effects. 

Fig. 3 Polarized infrared spectra of stretched polyacetylene films prepared by a mixture catalyst of Trihexyl aluminium and Tetradecyl titanate (a)perpendicular (b) parallel.

POLARIZED INFRARED SPECTRA OF TCNQ AND PERDEUTERO SINGLE CRYSTALS. 

Fig. 14 Polarized infrared spectra of sPS crystallized at lower temperatures (A) and at 260 °C (B). (a) represents the bulk, (b) nanorods prepared inside AAO with Dp = 200 nm, and (c) nanorods prepared inside AAO with Dp = 80 nm. Polarization perpendicular to nanorod axes solid lines polarization parallel to nanorod axes dashed lines. Reproduced from [101]. (2007) American Chemical Society...

Fig. 26. Polarized infrared spectra of polyethylene (a) CH2 rocking region (b) CH2 wagging and bending regions top is spectra with polarization parallel to the draw direction and bottom with polarization perpendicular to draw direction.

Figure 1.70. (c-d) Polarized infrared spectra of stretched polyacetylene samples with different stretching ratios, (c) draw ratio = 3.5 and (d) draw ratio = 4.5. (Reprinted with permission from ref 172)... 

By measuring the polarized infrared spectra of oriented semicrystalline polymers, information about both the molecular and crystal structure can be obtained. Both uniaxially and biaxiaUy oriented samples can be studied. 

Fig. 17a, b. Polarized infrared spectra (absorbance a vs. wavenumber v) of a salmon sperm DNA in (a) the A form and (b) the B form. The incident electric field is oriented perpendicular (solid line) and parallel (dotted line) to the DNA axis [85T1]. 

The polarized infrared spectra of polyoxymethylene and deuterated polyoxymethylene were measured by Tadokoro, Kobayashi, Kawaguchi, Kobayashi, and Murahashi (1963) and the Raman spectra were measured by Matsui, Kubota, Tadokoro, and Yoshihara (1965) with mercury source. The normal vibrations were calculated for the Ai,A2 and Ej species by Tadokoro, Kobayashi, Kawaguchi, Kobayashi, and Murahashi (1963). 

Fukushima,K., ldeguchi,Y. Molecular vibrations and structure of high polymers. III. Polarized infrared spectra, normal vibrations, and helical conformation polyethylene glycol. J. Chem. Phys. 12, 2764—2776 (1962). 

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