Poly infrared spectrum

Fig. 10.14. The transition of the a- to -poly-L-lysine, infrared spectra. Poly-L-lysine in D2O (0.24 %) at pD 12.3. Spectra were recorded at 15°C (spectrum 1), 34°C (spectrum 2), and 47°C (spectrum 3). (The dashed portion of curve 3 extended beyond the ordinate scale and has been estimated.) A jacketed CaFj cell of 0.05-mm optical path length was used. (Davidson and Fasman, 1967.)...

Successive 1,4 units in the synthetic polyisoprene chain evidently are preponderantly arranged in head-to-tail sequence, although an appreciable proportion of head-to-head and tail-to-tail junctions appears to be present as well. Apparently the growing radical adds preferentially to one of the two ends of the monomer. Which of the reactions (6) or (7) is the preferred process cannot be decided from these results alone, however. Positive identification of both 1,2 and 3,4 units in the infrared spectrum shows that both addition reactions take place during the polymerization of isoprene. The relative contributions of the alternative addition processes cannot be ascertained from the proportions of these two units, however, inasmuch as the product radicals formed in reactions (6) and (7), may differ markedly in their preference for addition in one or the other of the two resonance forms available to each. We may conclude merely that structural evidence indicates a preference for oriented (i.e., head-to-tail) additions but that the 1,4 units of synthetic polyisoprene are by no means as consistently arranged in head-to-tail sequence as in the naturally occurring poly-isoprenes. 

Pyridine was found to polymerize on a Pt electrode from a solution of 1 M pyridine in 1 M LiC104/CH3CN at potentials above 0.8 V vs Ag/AgCl. A colorless film was formed, but it could be oxidized and reduced when placed in plain electrolyte solution. The infrared spectrum of the electrochemically formed poly(pyridine) film is shown in Figure 5. It displays a very intense, narrow band at 1500 cm indicative of C=C stretches that are perpendicular to the surface. 3,5 Lutidine also was polymerized on a platinum electrode under the same conditions, and its infrared spectrum is similar to that for the surface catalyzed poly(lutidine). The C=C stretching band for the poly(lutidine)... 

A poly(pyrrole) film was deposited on a Pt electrode from potentiostatic conditions at 0.8 V vs Ag/AgCl. The film was colorless, its presence was verified by oxidation and reduction of the film in plain electrolyte solution. The infrared spectrum of the electrochemically prepared poly(pyrrole) is similar to the catalytically prepared films indicating the two films are structurally similar. 

Fig. 14.5 Infrared spectrum of poly(vinyl chloride) (a) transmittance and (b) absorbance.

Figure 3. Infrared spectrum of poly(p-formyloxystyrene) (a) unexposed...

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.

Coleman et al. 2471 reported the spectra of different proportions of poly(vinylidene fluoride) PVDF and atactic poly(methyl methacrylate) PMMA. At a level of 75/25 PVDF/PMMA the blend is incompatible and the spectra of the blend can be synthesized by addition of the spectra of the pure components in the appropriate amounts. On the other hand, a blend composition of 39 61 had an infrared spectrum which could not be approximated by absorbance addition of the two pure spectra. A carbonyl band at 1718cm-1 was observed and indicates a distinct interaction involving the carbonyl groups. The spectra of the PVDF shows that a conformational change has been induced in the compatible blend but only a fraction of the PVDF is involved in the conformational change. Allara M9 250 251) cautioned that some of these spectroscopic effects in polymer blends may arise from dispersion effects in the difference spectra rather than chemical effects. Refractive index differences between the pure component and the blend can alter the band shapes and lead to frequency shifts to lower frequencies and in general the frequency shifts are to lower frequencies. 

There are advantages in the Raman field over its absorption counterpart. Thus, many of the functional groups which, due to their very high (dfijdq) values, tend to obscure the infrared spectrum (e.g. vC-O-, vC-F, vO-H and <50-H) rarely give any trouble in this respect in the Raman effect. Those familiar with the infrared spectrum of poly-(tetra-fluoro ethylene) or of polyoxymethylene will confirm this when they compare their data with Fig. 10 and 11, respectively. In addition, all the spectra given in this review were recorded on readily available samples — with no sample preparation. 

Poly(a-phenylethyl isocyanide), however, yields complex products distinguishable from monomer upon thermal degradation at 20 mm Hg (13). At 300° C a viscous condensate is produced which is free of isocyanide absorption in its infrared spectrum and appears very similar to the recently synthesized oligo-isocyanides, a,co-dihydrotri(a-phenylethyl isocyanide) and a,co-dihydrohexa(a-phenylethyl isocyanide) (15). Pyrolysis at 500° C produces an intense broad infrared absorption band in the range about 3300 cm-1, which is the range of associated N il bonds. Pyrolysates obtained at 700° C reveal nitrile absorption at 2270 cm"1, that becomes more intense in pyrolysates produced at temperatures up to 1300° C. A slow pyrolysis at 200-300° C is indicated for the study of primary structural changes in poly(a-phenylethyl isocyanide). Pyrolysates of poly(<7-... 

The formation of block copolymers from styrene-maleic anhydride and acrylic monomers was also indicated by pyrolytic gas chromatography and infrared spectroscopy. A comparison of the pyrograms of the block copolymers in Figure 7 shows peaks comparable with those obtained when mixtures of the acrylate polymers and poly(styrene-co-maleic anhydride) were pyrolyzed. A characteristic infrared spectrum was observed for the product obtained when macroradicals were added to a solution of methyl methacrylate in benzene. The characteristic bands for methyl methacrylate (MM) are noted on this spectogram in Figure 8. 

Gel permeation chromatography (GPC) of poly(methyl methacrylate) and cellulose nitrate showed elution volume peaks at 62.5 ml for PMMA and at 87.5 for cellulose nitrate (Figure 5), due to their difference in molecular weight. A mixture of poly(methyl methacrylate) and cellulose nitrate of the same ratio as that of the graft copolymer was recorded and two peaks in elution volume at almost identical positions were observed. This shows that the constituent homopolymers retain their identity in a physical mixture. The isolated graft copolymer showed a single peak in elution volume at 80.0 ml. The second peak in elution volume is absent in spite of poly(methyl methacrylate) attached to cellulose nitrate as revealed by infrared spectrum. Hence, these results indicate that GPC can be used as a technique to differentiate between homopolymer, physical mixture, and graft copolymer. 

The Raman spectra of poly maleic acid are shown in Figure 3 for pH 8 (spectra A), pH 5 (spectra B), and pH 2 (spectra C). Changing the pH causes less change in these spectra than for the infrared spectra. The symmetric C=0 stretch at 1615 cm in acidic solution corresponds to the asymmetric stretch in the infrared spectrum at 1714 cm . The existence of this pair of bands in the infrared and Raman is unambiguous evidence for dimerization of the carboxyl (27), indicating internal hydrogen bonding between the maleic acid units within the polymer. The symmetric COO- stretch appears at 1388 cm and shifts to 1380 in the protonated acid form. 

Hydroxyethyl functionalities can be anchored to poly(styrene-DVB) by reacting lithiated resin with ethylene oxide (15). A THF suspension of lithiated resin (2 g in 50 ml) was cooled to -80°C, and 15 ml of ethylene oxide at -80°C were added with a transfer pipet. The mixture was brought to room temperature (in about 3 hr) and the beads were separated by filtration, washed successively with THF H20 (3 1), 10% HC1, H2O, THF, and ether, and then vacuum dried at 70°C. The infrared spectrum showed an OH absorption. 

Fig. io. Infrared spectrum of /3-poly(L-alanine). (a) Mid-infrared region. (-----------)... 

The photodegradation of poly(2,6-dimethyl-l,4-phenylene oxide), 1, has received considerable attention both in industrial and in academic laboratories. Workers have observed that when poly-(phenylene oxide) films are exposed to light of wavelengths greater than 300 nm in the presence of oxygen, considerable discoloration and crosslinking occur accompanied by the appearance of carbonyl and hydroxyl bands in the infrared spectrum (2-5). Most workers in the field have ascribed these results to a hydroperoxide-mediated free radical oxidation of the benzylic methyl groups (Scheme I). 

Preparation of poly(amlc acids). Prepared by mixing the dianhydrides with equimolar amounts of diamines for 5 hours at 50°C. A golden brown solid, recovered by precipitation into water showed the presence of both amide and acid functionality in the infrared spectrum. 

Increased absorption in the hydroxyl and carbonyl regions of the infrared spectrum has been observed on irradiation of poly-2,6 dimethyl-1,4-phenylene oxide ... 

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