Poly crystalline bands

I. R. spectra of polymers of optically active and racemic monomers (12) having similar stereoregularity are identical in the case of poly-5-methyl-l-heptene, but slightly different in the case of poly-3-methyl-l-pentene and poly-4-methyl- 1-hexene. A very characteristic crystallinity band has been found in the I. R. spectrum of poly-5-methyl-l-heptene at 12.06 fi bands which seem connected with stereoregularity have been found in the I. R, spectrum of poly-4-methyl-l-hexene at 10.06 fi the nature of these bands has been proved when preparing a practically atactic sample by hydrogenation of poly-4-methyl-l-hexyne (24). 

Investigations were made on the I. R. spectra of poly-[(S)-l-methyl-propylj-vinyl-ether and poly-[(S)-2-methyl-butyl]-vinyl-ether (65) a band at 911 cm-1 related to stereoregularity was detected in the spectrum of the former while a crystallinity band at 827 cm-1 was found in the latter. The spectra of polymers obtained from an optically active or a racemic monomer did not reveal any remarkable difference. 

Iqbal et al (Ref 56) measured the transmission infrared and laser excited Raman spectra of poly crystalline RDX in the range of 40 to 4000/cm. To aid assignments in the spectral region of 400 to 4000/cm, the spectra of two types of N15-labeled samples and the soln spectra in different solvents were also recorded. From these data it was possible to assign many of the observed bands to intramolecular modes of the RDX molecule. The Raman-active lattice modes also were resolved and found to be comparable to the lattice mode frequencies in solid cyclohexane... 

In conclusion, the deformation behavior of poly(hexamethylene sebacate), HMS, can be altered from ductile to brittle by variation of crystallization conditions without significant variation of percent crystallinity. Banded and nonbanded spherulitic morphology samples crystallized at 52°C and 60°C fail at a strain of 0.01 in./in. whereas ice-water-quenched HMS does not fail at a strain of 1.40 in./in. The change in deformation behavior is attributed primarily to an increased population of tie molecules and/or tie fibrils with decreasing crystallization temperature which is related to variation of lamellar and spherulitic dimensions. This ductile-brittle transformation is not caused by volume or enthalpy relaxation as reported for glassy amorphous polymers. Nor is a series of molecular weights, temperatures, strain rates, etc. required to observe this transition. Also, the quenched HMS is transformed from the normal creamy white opaque appearance of HMS to a translucent appearance after deformation. 

Polymerization of Cyclic Ethers and Formats by Poly-THF Dioxolenium Salt. The polymerization of cyclic ethers and formals by PTHF-dioxolenium salt was carried out to clarify the presence of termination or transfer reactions. The results are shown in Table IV. In the polymerization of 3,3-bischloromethyloxetane (BCMO), block copolymer soluble in chloroform and having the expected molecular weight was formed the homopolymer of BCMO insoluble in chloroform was not observed. The block copolymer showed crystalline bands of BCMO at 700, 860, and 890 cm 1, suggesting the formation of ABA block. 

The structure of the electrochemical double layer in the presence of adsorbed molecules can be investigated with ERS. In a typical study, Schmidt and Pli-eth [100] have investigated the adsorption of p-nitroaniline on a poly crystalline platinum electrode from sulfuric acid solution. The ER spectrum as displayed in Fig. 5.19 shows two distinct bands when light polarized parallel to the plane of reflection is used (with light polarized perpendicular, only a flat baseline was found). 

An example of this is syndiotactic poly(propylene). The ir spectrum has a pronounced crystalline band at 868 cm" for the stablest crystalline state. According to theoretical considerations, this band, (see Figure 4-10), is practically entirely due to helical (TTGG) conformations. The band disappears on melting. 

Figure 4-12. Variation with temperature of the ratio of the absorption at 868 cm" ( crystalline bands) to that at 972 cm" (reference band) of a ( 4 X 10" g/ cm ) solution of st-poly(propylene) in benzene (O) and in carbon tetrachloride ( ) solution (After B. Stofer and H.-G. Elias).

The existence of ordered conformational sequences can be directly identified experimentally with some solutions of macromolecules. For example, the IR spectrum of crystalline st-poly(propylene) possesses a so-called crystalline band at 868 cm which disappears on melting. Theoretical calculations show that this band results almost exclusively from the helix structure of the polymer. The band does not occur with poly(propylene) solutions in CCI4 but does occur with solutions in benzene. The intensity of the band decreases with increasing temperature of the solution The helices melt (Figure 4-8). 

The most frequently encountered acid is adipic, but others are also employed in polyurethanes. Polyurethanes prepared from poly(ethylene glycol) adipate and 1,5-naphthalene diisocyanate produce two strong absorptions at 750 cm and 735 cmwhile the urethane from poly(ethylene glycol) sebacate and 1,5-naphthalene diisocyanate shows crystallinity bands at 722, 729, 754, 860, 881 and 895cm" ... 

True crystallinity bands have been observed for only a few polymers and their origin experimentally verified by isotopic dilution studies [70]. We may quote the classical prototype case of orthorhombic polyethylene [68, 69], orthorhombic poly-oxymethylene [71], and-with caution-possibly a few others [72, 73]. 

The degree of crystallinity of swollen polyfvinyl alcohol) has been measured by laser Raman spectroscopy from the relative intensity of the amorphous band at 1124 cm . The crystalline band, at 1147 cm, was not considered quantitative. Polyacetylene,poly(vinylidene fluoride), polyfdiphenyl siloxane), poly-(butylene terephthalate), poly(decamethylene oxide), polypropylene and copolymers, poly(methyl methacrylate), poly(ethylene terephthalate), polystyrene, polycarbonate, polyalkylene, poly(oxymethylene), and poly (ethylene oxide) have all been studied either by WAXS or thermal analysis. 

FIGURE 17.24 Crystallinity band of poly(vinyl alcohol). H-V, IA3, and S-A are three different samples [Source Kennedy and Willcockson (1966). By permission of John Wiley Sons.]... 

Crystallinity Crystallinity bands are often assigned for polymer molecules in conjunction with the parameters of other techniques, such as density and x-ray diffraction. They describe the state of order in an investigated polymer molecule. In the spectmm of poly(vinyl alcohol), for example, the absorption band at 1141 cm is assigned to the crystallinity of the molecule. The degree of crystallinity is measured by the intensity of the band at 1141 cm which matches the density of the molecule. Figure 17.24 shows this phenomenon. 

Ozaki et al. [106] studied blends of poly(R)-3-hydroxybutyrate) (PHB) and PLLA using FTIR microspectroscopy, and showed that crystalline bands were observed due to PHB, whereas those due to PLLA were hardly observed for all PHB/PLLA blends investigated. On the other hand, some crystalline bands of PLLA were observed in the microinfrared spectra of some spots in the 20/80 PHB-co-HHx/ PLLA blend. Microinfrared spectra also showed a significant difference in the compatibility and crystalline structures between the PHB-co-HHx/PLLA and PHB/PLLA blends. Figure 20.25a and b show microinfrared spectra in the 2000-1000cm region of PHB/PLLA and PHB-co-HHx/PLLA blends with 80/20 and 20/80 blending ratios. The differences in the infrared spectra between neat PHB and PHB-co-HHx lie mainly in the intensities of the crystalline and amorphous bands. The ratios of peak intensities of PHB and PLLA bands were dependent on the measurement points in both blends. In the 80/20 PHB/PLLA blend, the spectra of many spots were similar to the crystalline PHB spectrum, but the main... 

Here m is the mode order (m — 1,3,5. .., usually 1 for polyethylenes), c the velocity of light, p the density of the vibrating sequence (density of pure crystal) and E the Young s modulus in the chain direction. The LAM band has been observed in many polymers and has been widely used in structural studies of polyethylenes [94—99,266], as well as other semi-crystalline polymers, such as poly (ethylene oxide) [267], poly(methylene oxide) [268,269] and isotactic poly(propylene) [270,271], The distribution of crystalline thickness can be obtained from the width of the LAM mode, corrected by temperature and frequency factors [272,273] as ... 

Due to the side chains this poiymer is amorphous with a glass transition temperature of 185 °C. In contrast, unsubstituted poly(arylene ether ketone)s are crystalline and high melting (T > 300 °C).The iR spectrum shows absorption bands at 3300 cm" and 1710-1730 cm" for the acid group in the side chain and at 1650 cm" for the keto group. 

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