IR spectra of polymers

The resulting styrene/maleic acid copolymer is soluble in hot water, in contrast to the starting material the aqueous solution of the product gives a distinctly acid reaction. The disappearance of the anhydride moiety can be verified by IR or C-NMR spectroscopic methods.The IR spectra of polymers should be recorded from a film of the sample prepared on a KBr pellet (freshly made from KBr powder). For this, a drop of a solution of the polymer in a low-boiling solvent (e.g.,THF, methylene chloride) is placed on the pellet.The residual solvent can often be removed directly in the IR beam.The resulting spectra are characterized by their sharp bands. 

On the other hand, the study of the effect of temperature on LC polymers allows to trace changes in structural ordering of individual macromolecular fragments. From polarized IR spectra of polymers IX and X 74,89)... 

Figure 3. IR-spectra of polymer films without high wave number 1645 Cm. nanoparticles (a), Ag-Au was added to PEPC solution (b) At the Same time, changes in and Ag-Au was synthesized in polymer mediate). band at 1328 cm 1...

Many digital spectral libraries have been transformed from printed spectra collections. Well known printed collections are the Aldrich spectra collection [1], the Sadder spectra collection [2-4], the Schrader-Meyer Adas of IR and Raman spectra [5], the Hummel collection of IR spectra of polymers [6], the Merck IR Adas [7] and the Buback collection of NIR spectra [8]. IR spectra have the largest share of digital optical spectra, followed at a clear distance by Raman spectra. Larger collections of UV/VIS spectra have not been estabhshed due to their missing fingerprint capability and to the strong sensitivity of the UV/VIS spectra to solvent interactions. A variety of dedicated spectra collections have been created in industrial laboratories without access to the public. 

Modern commercial IR spectrometers operating with the aid of a Michelson interferometer produce interferograms, which, upon mathematical decoding by means of the Fourier transformation, deliver absorption spectra commonly referred to as Fourier-transform infrared (FTIR) spectra [50]. Comprehensive collections of IR spectra of polymers, monomers, and additives are available [51]. Moreover, the reader s attention is directed to several books [52-58]. 

Figure 4.4 shows some internal reflectance IR spectra of polymer films obtained using a Perkin Elmer 1760 FT-IR spectrometer. Using a room temperature detector, spectra measurements were made for two minutes at 4 cm" resolution. Two different reflection accessories were used. Pellets, powders, and fibres were measnred with a Spectra-Tech Collector accessory. This is well suited to measuring snrface reflection from small samples. Larger samples such as moulded products are measured with a Harrick specular reflection accessory with an horizontal sample stage. 

Particular studies of the IR spectra of polymers include isotactic poly(l-pentane), poly(4-methyl-l-pentene), and atactic poly(4-methyl-pentene) [18], chlorinated PE [19], aromatic polymers including styrene, terephthalic acid, isophthalic acid [20], PS [21, 22], styrene-glycidyl-p-isopropenylphenyl ether copolymers [23], styrene-isobutylene copolymers [24], vinyl chloride-vinyl acetate-vinyl fluoride terpolymers [25], vinyl chloride-vinyl acetate copolymers [26], styrene copolymers [27], ethylene-vinyl acetate copolymers, graft copolymers, and butadiene-styrene [28] and acrylonitrile-styrene copolymers [29]. 

Figure 2. IR Spectra of Polymer Synthesized from Di(p-iso-cyanatophenyl) Methane (Spectrum 1), and the Polymer after Being Thermally Degraded for 20 Minutes (Spectrum 2) at 118 C and for Additional 25 Minutes at 148°C (Spectrum 3)...

On standing, a solution of TCNQ and carbazole polymer in dioxane (polymer TCNQ mole ratio was 1 2) gave a black crystalline precipitate. The complex had Tm=193 C and Tg=114 C (which is almost the same as that of homopolymer). The elemental analysis of the complex showed C, 74.22% H, 5.60%, N, 14.35%. This indicates the mole % of pol3nner, TCNQ and dioxane in the complex are 52.89%, 31.16% and 15.95% respectively. The IR spectra of polymer-TCNQ mixture (polymer TCNQ mole ratio was 55 45) and the complex are shown in Figure 8. The intensities as well as the positions of TCNQ bands are changed when TCNQ was complexed with polymer. C=N stretch bands of the complex appear at 2218 and 2179 cm which were shifted 6 and 45 wavenumbers from 2224 cm which is the C=N stretch band of pure TCNQ. The 2218 cm band is due to the charge transfer complex. 

An extensive literature on the infrared (ir) spectra of polymers exists (Zbinden, 1964 Henniker, 1967). Fortunately the ir spectra of functional groups anchored on polymers do not differ appreciably from those in small molecules, and the technique of taking the spectra of polymeric solids (film, mull, or KBr pellet) is well-developed. The sensitivity attained is approximately the same as that with the small molecules. Infrared spectroscopy has been particularly useful in following polymeric transformations. The characteristic absorption due to a particular functional group often disappears completely on chemical transformation, with a simultaneous appearance of the characteristic absorption of the new group(s). Thus, the completion of a reaction can be easily followed by scanning the ir spectra of reactant and product. Letsinger er aL (1964), Blackburn et aL (1969), and Farrall and Frechet (1976) have made extensive use of ir spectra to follow chemical transformations in polymers. 

Figure 1. IR Spectra of polymer-glass composite at different reaction times.

Today polymers scientists rely on many different methods of instrumental analysis to develop, test, and classify macromolecules. Infrared (IR) spectroscopy, one of the most important analytical tools in research as well as in manufacturing, is used to test the quality of incoming monomers, to control processes, to control quality control, and to confirm quality of intermediates and final products. IR is even used to troubleshoot processing problems and to analyze the competitor s products. IR spectroscopy has value in structure elucidation and quantitative analysis of polymers. Hausdorff [6] and Kagarese and Weinberger [7] were the first to publish collections of IR spectra of polymers. 

Ciampelli and co-workers [14] developed two methods based on IR spectroscopy of carbon tetrachloride solutions of polymers at 7.25, 8.65 and 2.32 pm for the analysis of ethylene-propylene copolymers containing >30% propylene. One method can be applied to copolymers soluble in solvents for IR analysis, the other can be applied to solvent-insoluble polymer films. The absorption band at 7.25 pm due to methyl groups is used in the former case, whereas the ratio of the band at 8.6 pm to the band at 2.32 pm is used in the latter. IR spectra of polymers containing 55.5 and 85.5% ethylene are shown in Figure 4.1. 

Kossler and Vodchnal [47] concluded that the IR spectra of polymers containing cis-1,4, trans-l,A and 3,4 or cyclic structural units are not additively composed of the spectra of stereoregular polymers containing only one of these structures. 

Very recently, a tuneable CO2 laser has been combined with an AFM to form an aperture-less nearfield imaging system to obtain contrast in infrared absorption on a scale of about 100 nm [299]. However, the tuneable range of the CO2 laser is limited to a region of the IR spectrum that is not particularly informative for most IR chromophores ( 2300 cm ). For many applications coupling of a tuneable IR diode laser to an infrared microscope [300] is more attractive. Hammiche et al. [301] have used a Wollaston resistive thermometer as a photothermal probe to record IR spectra of polymers. Anderson [302] has indicated that an AFM/FTIR microscope without specialised tips can provide surface topography and chemical mapping at high spatial resolution. Direct infrared detection at a surface with the use of an AFM was tested both with filter and FTIR spectrometers (Fig. 5.6). Nowadays, IR spectroscopy at... 

There are two general ways of doing this (1) to study the IR spectra of polymer solutions at low temperatures (54,63,65) (2) to study the IR spectra of carefully crystallized products (11,44,65). 

IR spectra of polymers were obtained by a diffraction grating infrared spectrophotometer (Jasco, Model DS-701G). 

The IR spectra of polymers [3] and [6J, taken in a nujoi mull, exhibit a band at about 1730 The absence of the band due to the olefinic double bond is indicative of the form.ation of the target polymers. 

The subject of this review is the IR spectra of polymers in the frequency range situated between the radio and the mid-infrared regions, usually called by molecular spectroscopist the far infrared region. 

Fig. 8.11. IR spectra of polymer I in an unoriented state (1) and in an elearic field with a strength of 20 kV/cm (2) [38].

Sample handling is the same for both types of spectrometer and use is made of salts such as potassium bromide and sodium chloride which do not absorb in the IR region. Solid polymers usually are analysed in the form of either (i) discs pressed from finely powdered dilute (1-2 per cent) dispersions of polymer in potassium bromide, or (ii) melt-pressed or solution-cast thin films. Liquid polymers are analysed as thin films between the polished faces of two blocks (known as plates) of sodium chloride. Analysis of polymers in solution tends to be avoided where possible because a significant proportion of the IR spectrum of the polymer is obscured by the IR absorptions of the solvent. IR spectra of polymer surfaces can be recorded using techniques such as attenuated total reflectance and specular reflectance, and their use has grown with the increasing importance of polymer surface chemistry. 

These IR spectra of polymer 3c-e on silicon wafer in the presence of triphenylsulfonium triflate during irradiation at 250 tun indicated tautomeric change of the alko Q pyrimidine to uracil. From the results of IR spectra, sensitivities of these pofymers were calculated (Figure 10). The highest sensitivity was obtained for the pofymer 3e. For the complete reaction of the polymer 3e, the UV dose of 10 mJ/cm and a post-bake at 60 C are suffident. Polymer 3d from the secondary diol shows a sensitivity of 100 mJ/cm. However, the sensitivity of polymer 3c, prepared from the primary diol was very low even after postbaking at 100 °C. 

Figure 7. IR spectra of polymer 3c with triphenylsulfonium trifluoromethanesul> fonate (10 wt%) in solid film. E qiosure 250 nm.

A final twist to the interpretation of the IR spectra of polymers is that apparently conformational isomerism is also present in these materials. Thus,... 

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