Polymers infrared spectra

Figure 6 Vibrational spectra of polymers, (a) Transmission infrared spectrum of polyethylene (b) electron-induced loss spectrum of polyethylene (c) transmission infrared spectrum of polypropylene. ...

All attempts to isolate efficient process giving a white solid polymer which appears to have repeating keteneimine units. This assignment is consistent with the very strong absorption at 2140 cm.-1 in the infrared spectrum. ... 

Plutonium(IV) polymer has been examined by infrared spectroscopy (26). One of the prominent features in the infrared spectrum of the polymer is an intense band in the OH stretching region at 3400 cm 1. Upon deuteration, this band shifts to 2400 cm 1. However, it could not be positively assigned to OH vibrations in the polymer due to absorption of water by the KBr pellet. In view of the broad band observed in this same region for I, it now seems likely that the bands observed previously for Pu(IV) polymer are actually due to OH in the polymer. Indeed, we have observed a similar shift in the sharp absorption of U(0H)2S0ir upon deuteration (28). This absorption shifts from 3500 cm 1 to 2600 cm 1. 

Many characteristic molecular vibrations occur at frequencies in the infrared portion of the electromagnetic spectrum. We routinely analyze polymers by measuring the infrared frequencies that are absorbed by these molecular vibrations. Given a suitable calibration method we can obtain both qualitative and quantitative information regarding copolymer composition from an infrared spectrum. We can often identify unknown polymers by comparing their infrared spectra with electronic libraries containing spectra of known materials. 

Figure 5 Infrared spectrum of block copolymer residue after Soxhlet extraction of PVA core polymer with acetonitrile.

The unique appearance of an infrared spectrum has resulted in the extensive use of infrared spectrometry to characterize such materials as natural products, polymers, detergents, lubricants, fats and resins. It is of particular value to the petroleum and polymer industries, to drug manufacturers and to producers of organic chemicals. Quantitative applications include the quality control of additives in fuel and lubricant blends and to assess the extent of chemical changes in various products due to ageing and use. Non-dispersive infrared analysers are used to monitor gas streams in industrial processes and atmospheric pollution. The instruments are generally portable and robust, consisting only of a radiation source, reference and sample cells and a detector filled with the gas which is to be monitored. 

Infrared Spectrum. The plasma polymerized organic film shows features distinctive from the conventional polymer. According to ESR measurements (31), the film contains a high concentration of residual free radicals, which showed a relatively long life time. The free radicals were oxidized in air and the oxidization is promoted significantly at elevated temperatures. The film is not soluble in usual solvents and it is more thermally stable than the conventional polymers. These properties are thought to be caused by the highly crosslinked structure of the film (32). 

Infrared spectra. An FT infrared spectrum of HTE liquid polymer (fan -500) is shown in Figure 2. All spectra of HTE polymers show characteristic absorptions a broad band at 3530 cm-1- for the hydroxyl stretching, three bands at 2958, 2913, and 2875 cm-1 assigned to the carbon-hydrogen stretching, an extremely strong... 

Experiments at high pressure have shown that the P-T phase diagram of butadiene is comparatively simple. The crystal phase I is separated from the liquid phase by an orientationally disordered phase II stable in a narrow range of pressure and temperature. The strucmre of phase I is not known, but the analyses of the infrared and Raman spectra have suggested a monoclinic structure with two molecules per unit cell as the most likely [428]. At room temperature, butadiene is stable in the liquid phase at pressures up to 0.7 GPa. At this pressure a reaction starts as revealed by the growth of new infrared bands (see the upper panel of Fig. 25). After several days a product is recovered, and the infrared spectrum identifies it as 4-vinylcyclohexene. No traces of the other dimers can be detected, and only traces of a polymer are present. If we increase the pressure to 1 GPa, the dimerization rate increases but the amount of polymer... 

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. 

Materials and Methods. The isomeric compositions of the four polybutadienes used are listed in Table I. Samples were prepared for infrared measurement from solutions of the polymer without further purification. Most films were cast from carbon disulfide solutions on mercury or on glass plates, but a few films were cast from hexane solutions to determine whether or not the solvent affected the radiation-induced behavior. No difference was observed for films cast from the different solvents. The films were cured by exposure to x-rays in vacuum. (Doses were below the level producing detectable radiation effects.) They were then mounted on aluminum frames for infrared measurements. The thicknesses of the films were controlled for desirable absorbance ranges and varied from 0.61 X 10 s to 2 X 10 3 cm. After measuring the infrared spectrum with a Perkin-Elmer 221 infrared spectrophotometer, the mounted films were evacuated to 3 microns and sealed in glass or quartz tubes (quartz tubes only were used for reactor irradiations). 

The carbonyl stretching band in the infrared spectrum of isotactic poly (a,a-dimethylbenzy 1 methacrylate) prebaked at 142°C for 1 hr indicated the formation of a small amount of acid group during the prebake, while the atactic polymer showed no change in the spectrum at this temperature. This may be the reason why the isotactic polymer showed a lower 7-value than the atactic polymer (Table III). 

Table VII the electron-beam exposure characteristics are given for the soluble poly (triphenylmethyl methacrylate-co-methyl methacrylate)s. The sensitivity on alkaline development was strongly influenced by the copolymer composition. The highest sensitivity was obtained on the copolymer containing 93.7 mol% methyl methacrylate. The copolymer of highest sensitivity showed the 7-value of 6.3, which was nearly twice as large as that for poly(methyl methacrylate). Formation of methacrylic acid units on exposure is obvious from the infrared spectrum. However, the mechanism of the occurrence should be different from the case of the a,a-dimethylbenzyl methacrylate polymer since there are no /3-hydrogen atoms in the triphenylmethyl group, and may be similar to the case of poly (methyl methacrylate). This will be explored in the near future.

We therefore studied the effect of temperature and of concentration on the position of the hydroxyl peak in simple alcohols (methanol, ethanol, etc.) in the pure state, and in carbon tetrachloride or chloroform solutions. Some of the results of this work have already been reported [1]. A plot of peak position against concentration gives curves such as that in Fig. la. Interpretation of this type of curve from the N.M.R. data alone is impossible. It is clear that several different species (monomer, dimer, polymers) are contributing their effect, but because of the averaging phenomenon only a single OH peak, representing the weighted mean of all these species, is observed. We have now used infrared spectral data to clarify the situation. A careful examination of the infrared spectrum of all normal aliphatic alcohols... 

Consequently we next searched for a molecule sufficiently hindered to prevent polymer formation but readily able to form dimer. Such a molecule is methyl ethyl tertiary butyl carbinol. The infrared spectrum makes it clear that this molecule forms only dimer. A comparison of the equilibrium constant for this substance with that for the... 

Propargyl alcohol HC = 0—CHgOH ako gives an infrared spectrum indicative of only a monomer dimer equilibrium, although since here there can be no steric hindrance there is no obvious reason why this should be the case. Its nuclear resonance shift with dilution is more akin to the kind shown by polymer-forming alcohols, and the anomaly... 

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