Butadiene, infrared absorption

Chemical methods for structure determination in diene pol3 mers have in large measure been superseded by infrared absorption techniques. By comparing the infrared absorption spectra of polybutadiene and of the olefins chosen as models whose ethylenic structures correspond to the respective structural units, it has been possible to show that the bands occurring at 910.5, 966.5, and 724 cm. are characteristic of the 1,2, the mns-1,4, and the m-1,4 units, respectively. Moreover, the proportion of each unit may be determined within 1 or 2 percent from measurements of the absorption intensity in each band. The extinction coefficients characteristic of each structure must, of course, be known these may be assigned from intensity measurements on model compounds. Since the proportions of the various units depend on the rates of competitive reactions, their percentages may be expected to vary with the polymerization temperature. The 1,2 unit occurs to the extent of 18 to 22 percent of the total, almost independent of the temperature, in free-radical-polymerized (emulsion or mass) poly butadiene. The ratio of trans-1,4 to cfs-1,4, however,... 

The butadiene (80%)-acrylonitrile(17%)-aerylamidoxime(3%) terpolymer was prepared by reacting 2.5g butadiene 80%)-acrylo-nitrile(20%) copolymer (Aldrich) in 150 ml xylene with 1.61g hydro-xylamine hydrochloride in 12 ml n-butanol (freed of HC1 immediately before addition by method of Hurd (4) by dropwise addition under nitrogen. Reaction time and temperature were 23 hr. and 90-95°C. The polymer product was worked up by slowly adding the reaction mixture to 500 ml ether with rapid stirring. The precipitated polymer was allowed to settle, the supernate decanted and the polymer resuspended and washed with two 100 ml portions of ether followed by vacuum drying. Yield 2.04g (81%). Conversion of nitrile functional groups to amidoxime groups was 15% by infrared absorption. 

Identification Identify emulsion-polymerized Butadiene-Styrene Rubber latex and solid by comparing their infrared absorption spectra with the respective four typical spectra as shown in the section on Infrared Spectra. Prepare latex samples by first drying them at 105° for 4 h, then by dissolving them in hot toluene and evaporating on a potassium bromide plate. Prepare solid samples by dissolving them in hot toluene and evaporating on a potassium bromide plate. 

Figure 3.4-3 a Infrared absorption spectrum of butadiene at a pressure of 107 mbar at room temperature, thickness 10 cm b infrared emission spectrum of the same sample at T = 800 K compared to the emission spectrum of a black body of 800 K, recorded with Lcitz prism spectrometer (Gutberlet, 1978). 

One polymer was acrylonitrile-butadiene-styrene, ABS, pigmented with different colors blue, green, orange, yellow, and red. Studies of the effect of carbon black on infrared absorption were made by making mixtures of polyethylene with different levels of carbon black. 

Absorption spectra, 23 3 of fats and oils, 10 822-823 of polymethine dyes, 20 506-512 Absorption spectroscopy, infrared reflection, 24 114-116 Absorption towers, in sulfuric acid manufacture, 23 779 Absorptive probes, 11 150 ABS polymers, 10 205-207. See also ABS (acrylonitrile-butadiene-styrene) materials... 

Slade and Jonassen (192) treated ethyleneplatinous chloride, [Pt2Cl4-(C2H4)2], with butadiene, and obtained an unstable complex to which they ascribed the chlorine-bridged structure (XXXIV), on the evidence that its infrared spectrum showed a weak absorption at 1608 cm-1 due to the free double bond of each butadiene molecule. 

Studies by Teplyakov et al. provided the experimental evidence for the formation of the Diels-Alder reaction product at the Si(100)-2 x 1 surface [239,240]. A combination of surface-sensitive techniques was applied to make the assignment, including surface infrared (vibrational) spectroscopy, thermal desorption studies, and synchrotron-based X-ray absorption spectroscopy. Vibrational spectroscopy in particular provides a molecular fingerprint and is useful in identifying bonding and structure in the adsorbed molecules. An analysis of the vibrational spectra of adsorbed butadiene on Si(100)-2 x 1 in which several isotopic forms of butadiene (i.e., some of the H atoms were substituted with D atoms) were compared showed that the majority of butadiene molecules formed the Diels-Alder reaction product at the surface. Very good agreement was also found between the experimental vibrational spectra obtained by Teplyakov et al. [239,240] and frequencies calculated for the Diels-Alder surface adduct by Konecny and Doren [237,238]. 

Fig. 3.4-3 shows the infrared emission spectrum (the spectral radiance) of a sample of butadiene gas alp = 107 mbar in a cuvette v, th a thickness of 10 cm at 800 K, compared to the emi.ssion spectrum of a black body at the same temperature. It is interesting to note that - as theory predicts - the percentage emission of butadiene compared to that of a black body almost equals the percentage absorption of the same gas at room temperature as recorded with an ordinary spectrometer. 

As mentioned earlier, conformational isomerization about the formal single bonds of polyene systems is facile in the ground state, where it occurs with activation barriers on the order of 2-4 kcalmol in acyclic systems". The process also occurs in acyclic dienes upon direct excitation, as was shown by SquiUacote and coworkers using low temperature matrix isolation techniques, at temperatures where thermal conformational reequilibration is suppressed (10-20 K) " . Thus, direct irradiation of tzaMi-l,3-butadiene in an argon matrix at 15 K results in the efficient formation of the cis -conformer, distinguishable from the irani-conformer by its distinct UV absorption and infrared... 

Poly butadiene rapidly becomes crosslinked when irradiated in vacuo at 253.7 nm [54]. A decrease amounting to 80% of the original unsaturation is observed by infrared spectroscopy. Since no new unsaturation has been detected this decrease has been accounted for by cyclization. However, the absence of absorption at 1020 cm-1 implies that formation of cyclopropyl groups does not occur. Formation of a ladder polymer is also unlikely since all attempts to accomplish the free radical post-polymerization of 1,2-poly butadiene have been unsuccessful namely,... 

I.r. emission has been seen from the vibrationally excited CO2 product of MPD of vinylacetic and pyruvic acids, from hydrogen halides formed by chemical reaction of CI2 with H atoms produced in the MPD of various hydrocarbons, and of HBr with F and Cl atoms formed in the MPD of CFjCl. Infrared fluorescence from CjFjCl following MPA shows emission from both discrete levels and the quasicontinuum, with efficient intramolecular vibrational redistribution out of the pumped mode evident after absorption of only 2—3 photons. Emission in the i.r. has been seen following MPA in N2p4, and has been used to study the interconversion of perfluorocyclobutene to perfluoro-butadiene isomers following MPA. Further isomerization reactions induced by CO2 lasers have been reported. 

Where the polymer material is a copolymer it is often possible to obtain a measurement of the relative amounts of the various monomer components from an infrared spectrum. For example, with an ethylene-vinyl acetate copolymer the relative heights of absorption bands from both the ethylene and vinyl acetate are measured and ratioed with the spectrum recorded in the absorbance mode. The most convenient absorbance bands are 720 cm for polyethylene and 1235 or 1740 cm for vinyl acetate. Copolymers of known composition are required for calibration. It is possible to obtain an assessment on the butadiene and acrylonitrile contents in styrene/ butadiene/acrylonitrile copolymers. The bands usually used are for styrene 1600 cm, for acrylonitrile 2240 cm and for butadiene 996 cm... 

Fraga [11] has also described an infrared thin-film area method for the analysis of styrene-butadiene copolymers. The integrated absorption area between 6.6 and 7.2 pm has been found to be essentially proportional to total bound butadiene, and is independent of the isomeric type of butadiene structure present. This method can be calibrated for bound styrene contents ranging from 25 to 100%. 

C/5-2,6 octadiene would be the most appropriate small molecular model for the repeat unit in m-poly(butadiene). However, in light of the fact that FeCCO) catalyzes double bond migration and isomerization any isomeric octadiene monomer should serve as an appropriate model for the polymer reaction. We reacted 1,7-octadiene with FeCCO) and obtained a simple infrared spectrum which was nearly identical to that for the reaction product of c/5-poly (butadiene) with Fe(C0)5, i.e., both materials displayed two discrete peaks in the carbonyl region, a sharp peak at 2050 cm and a broad absorption ( "30 cm HWHH) centered at 198O cm" (See Fig. 2). The broad unresolved character of the 1980 cm" band, as compared to that in rj -butadiene iron tricarbonyl which shows discrete sharp peaks at 1980 and 1990 cm in addition to the sharp peak at 2056 cm", can be understood in terms of the variety of isomeric diene iron tricarbonyls which can be formed in the reaction of FeCCO) with either c/5-poly(butadiene) or 1,7-octadiene. 

The adhesion of RFL-coated tire cords to rubber can be adversely affected if the dipped cords are exposed to ozone, UV light, nitrogen oxides, sulfur dioxide, or air before vulcanization into rubber. lyengar proposed that ozone exposure of RFL reduces adhesion because ozone attacks the double bonds of the butadiene component of the rubber latex and impairs its cocuring with the solid rubber compound. Infrared studies by Solomon reinforced this argument. When typical RFL films were exposed to ozone, the IR spectrum showed an increase in IR absorption at 1720 cm corresponding to an increase in the carbonyl content in the exposed film. An RFL film with no ozone exposure did not show this absorption at 1720 cm The increased carbonyl content is due to the reaction of some double bonds in the rubber with ozone and therefore, would leave fewer unsaturation sites for rubber crosslinking and adhesion. 

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