Spectra polybutadiene

FIGURE 30.7 Typical (averaged) torque traces as recorded when a gum polybutadiene sample is submitted to high strain the Fourier transform (FT) spectrum exhibits accordingly significant harmonic contributions the inset table gives the results of the automatic analysis of torque and strain signals. 

Figure 19. The predicted low T heat conductivity. The no coupling case neglects phonon coupling effects on the ripplon spectrum. The (scaled) experimental data are taken from Smith [112] for a-Si02 (AsTj/ScOd 4.4) and from Freeman and Anderson [19] for polybutadiene (ksTg/Hcao — 2.5). The empirical universal lower T ratio l /l 150 [19], used explicitly here to superimpose our results on the experiment, was predicted by the present theory earlier within a factor of order unity, as explained in Section lllB. The effects of nonuniversaUty due to the phonon coupling are explained in Section IVF.

This most simple model for the relaxation time spectrum of materials near the liquid-solid transition is good for relating critical exponents (see Eq. 1-9), but it cannot be considered quantitatively correct. A detailed study of the evolution of the relaxation time spectrum from liquid to solid state is in progress [70], Preliminary results on vulcanizing polybutadienes indicate that the relaxation spectrum near the gel point is more complex than the simple spectrum presented in Eq. 3-6. In particular, the relation exponent n is not independent of the extent of reaction but decreases with increasing p. 

Fig. B8.2.1. Temperature dependence of the fluorescence spectrum of DIPHANTdispersed in polybutadiene. Insert temperature evolution of the fluorescence intensity of monomer and excimer (reproduced with permission from Bokobza and Monnerie3 ).

Figure 9. Change in IR spectrum of 12-polybutadiene film containing 4,4 -di-azidodiphenyl with UV irradiation in vacuum, before (--) and after (---) irra-...

Figure 10 shows a spectrum of butyl rubber gum stock obtained on the solid at 80°C using normal pulsed FT techniques. Clearly it could be identified as a component in fabricated materials by direct nmr spectral analysis. Figure 11 shows spectra obtained from various portions of typical rubber products. These samples were cut from the rubber product, placed in an nmr tube without solvent, and spectra obtained at an elevated temperature. The data show how polyisoprene, a polyisoprene/polybutadiene blend and a polyisobutylene/polyisoprene/polybutadiene rubber blend are quickly identified in the materials. Figure 11a shows processing oil was present, and which was confirmed by solvent extraction. 

Compared to the NMR spectrum,of the polybutadiene (80% 1,2) initiator, new bands appear on the spectra of block polymers for each fraction (Figure 9). These bands correspond to the acrolein blocks attached to the polybutadiene chains. In particular we can observe the presence of ... 

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). 

Calculations. The spectrum of a typical high cis-1,4 polymer sample is shown before and after irradiation in Figure 1 and that of a trans-1,4 polymer film in Figure 2. The significant infrared bands are listed in Table II for all of the polybutadienes, with the assignments to the various modes of molecular oscillation as developed by Binder (2). The bands used to estimate quantitative changes in the olefin groups were those at 740 cm."1 for the cis isomer, 967 cm."1 for the trans isomer, and 910 cm."1... 

Spectra have been recorded of the following polymers Poly isobutylene. Schaufele has reported a spectrum of a non-turbid specimen of this material complete with depolarization data (18). Bands at Av - 2919 and 720 cm 1 are clearly polarized and must result from symmetrical modes. Schaufele was also able to show that the short chain hydrocarbon CH3(CH2)12CH3 could be examined satisfactorily but the results were very much sharpened by cooling to liquid air temperatures. Polyisoprene and Polybutadiene. Both of these in the cis form have also been examined at Southampton very recently. The trans isomers gave no spectra due to fluorescence but no interpretation has been attempted as yet. Spectra are shown in Fig. 7 and 8. 

The system Cl-buty 1-natural rubber (or cw-polyisoprene) could not be resolved by differential solvent techniques because the polymeric solubility parameters were too similar. At one end of the spectrum—i.e., with styrene at — 25 °C—natural rubber could be highly swollen while restricting the chlorobutyl swell, but the reverse was not possible, as indicated by the swelling volumes in the trimethylpentane. As displayed in Table II, attempts to use a highly symmetrically branched hydrocarbon with a very low solubility parameter, served only to reduce both the swelling of natural rubber and chlorobutyl. (Neopentane is a gas above 10°C and a solid below — 20°C). Therefore, for this report the use of differential solvents in the study of interfacial bonding in blends was limited to systems of Cl-butyl and cw-polybutadiene or SBR. 

The 13C-NMR spectrum of polybutadiene polymer made by this initiator shows characteristic resonance peaks at 110-114 ppm assigned to... 

Subsequently, several nonkinetic approaches (32) were directed toward determining the structure of the live chain ends (e.g., H-NMR and 13C-NMR). For example, Bywater and co-workers (58) studied the addition of r-butyllithium to 1,3-butadiene and obtained a complex PMR spectrum for the addition product. They examined the effect of catalyst concentration on the microstructure of the polybutadiene and found that at high catalyst levels, the vinyl content increased as shown in Table II. 

It should be noted that, unlike Ag nanocrystals of Ag-PPX nanocomposites with 2max of plasmon band in the range 430-445 nm, nanocrystals prepared by reduction of Ag+ ions in solution of poly (N-vinylpyrrolidone) [81] as well as nanocrystals formed by introducing Ag vapors into liquid polybutadiene [77] have plasmon band with 2max around 410 nm. As is specified in Ref. [81], the UV-vis spectrum of nanocrystals depends on their size and form as well as on the surrounding matrix. The plasmon band of Ag nanocrystals [77, 81] coincides with that of modeling spherical nanoparticles with a smooth ideal surface, which were theoretically treated from different points of view in Ref. [82, 83]. 

Baumgaertel M, De Rosa ME, Machado J, Masse M, Winter HH (1992) The relaxation time spectrum of nearly monodisperse polybutadiene melts. Rheol Acta 31(l) 75-82 Baumgarter A, Muthukumar M (1996) Polymers in disordered media. Adv Chem Phys 94 625-708. Eds I. Prigogine and S.A. Rice, Wiley, New York Berry GC, Fox TG (1968) The viscosity of polymers and their concentrated solutions. Adv Polym Sci 5 261—357... 

Since isomerically pure polymers were not available, three different kinds of BR, each relatively high in one of the three kinds of base units were used as standards [35]. The band near 1308 cm 1 was identified [38,39] with the cis isomer and used for analyses [43]. The 1308 cm 1 band is weak and relatively broad, with the appearance of an unresolved doublet (1306,1311 cm 1). The cis band at 730 cm 1 is more frequently used in spite of some difficulties. Relatively pure, crystalline stereoregular polymers have been prepared and structures were determined by X-ray diffraction for cis [44], trans [45] and syndiotactic vinyl [46] and isotactic vinyl [47]. Infrared spectra [48-50] have been published for the four stereoregular polybutadienes, with detailed analyses of the spectra and band assignments for cis [51], trans [51] and syndiotactic vinyl [51] polymers. For the spectrum of isotactic vinyl BR, bands at 1232, 1225, 1109, 943, 876, 807 and 695 cm"1... 

The determination of percentage of styrene and butadiene isomer distribution in copolymers is an extension of the methods for the analysis of polybutadiene. The styrene band at 700 cm 1 is largely independent of the sequence distribution and therefore useful in styrene content determination [76]. A series of bands in the IR spectrum of crystalline isotactic polystyrene at 758, 783, 898, 920, 1053, 1084, 1194, 1261, 1297, 1312 cm"1 have been attributed to the helical structure [77]. The absorption bands for butadiene in SBR are similar to BR structures (Table 3.2a). 

Network structure and reaction mechanisms in high pressure vulcanisation (HPV) and peroxide vulcanisation of BR was studied by 13C solid-state NMR [43]. Different samples of polybutadiene (51% trans, 38% cis, and 11 % vinyl) were peroxide cured with dicumyl peroxide on a silica carrier and by the HPV conditions of 250 °C and 293 MPa. The 13C NMR spectra from peroxide and HPV cures were compared to a control samples heated to 250 °C for 6 minutes under atmospheric pressure. Although no new isolated strong peaks were detected in either the peroxide or HPV vulcanisations, small increases in both spectra were observed at 29.5, 36.0, 46.5, and 48.0 ppm. These peaks compare favourably with calculated shifts from structures that arise from main chain radical addition to the pendent vinyl groups. These assignments are further reinforced by the observation that the vinyl carbon concentration is substantially reduced during vulcanisation in both peroxide and HPV curing. Two peaks at 39.5 and 42.5 ppm appear only in the peroxide spectrum. Cis-trans isomerisation was absent in both cures. 

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