Atactic Poly propylene

Figure 2 X-ray diffractograms recorded at room temperature, (a) Metallocene-synthesized isotactic poly(propylene), mmmm — 0.996 crystallized at 145°C. (b) Atactic poly(propylene). Reproduced with permission from Ref. [43], Copyright John Wiley Sons, Inc., 1999.

In one example, the Tics of the non-crystalline methyl, methine and methylene carbons of iPP, 70% crystalline, were compared at room temperature with those of model atactic poly(propylene), hydrogenated poly(2-methyl-l,3-pentadiene) [163]. It was found that, within the experimental error, the Tic values of each of the carbons were the same in both polymers. The conclusion can then be reached that the fast segmental motion, at or near the Larmor frequency of... 

MHz, which determine the Tics, are the same for the non-crystalline region of isotactic poly(propylene) and for atactic poly(propylene). This in turn indicates that the disordered chain structure is the same for the two cases. 

Fig. 5.12 Molecular structure of atactic poly(propylene oxide).

Figure 10-22. The glass transition temperature as a function of the number N of chain units for poly(o -methyl styrene), poly(methyl methacrylate), poly(vinyl chloride), iso- and atactic poly(propylene), and poly(dimethyl siloxane) (J. M. G. Cowie).

Atactic poly(propylenes) (APP) can also be produced directly. They are used in industry for paper laminates, carpet backings, mixing with bitumens, etc. 

Because of its high tensile strength and stress corrosion resistance, poly-(butene-1) is used for pipes and packaging film. Atactic poly(butene-l) (APB) is mostly produced by direct polymerization. It has similar properties to atactic poly (propylene). Syndiotactic poly (butene-1) is obtained by hydrogenating 1,2-poly (butadiene) however, it has no commercial significance. 

HCH3 HCH3H3CH HCH3 atactic poly (propylene)... 

Atactic poly(propylene)/Poly(butene) Polyurethane... 

FIGURE 12.2A An NIR wavelength spectrum of atactic poly(propylene) at low resolution (32 cm )-... 

Fig. 4. 220 MHz spectra of atactic poly propylenes prepared from (a) trans- and (b) cis-1,2,3,3,3-45-propylene (refs. 6—8)...

Fig. 5. Experimental spectrum of atactic poly(propylene) recorded at T = 260 K, below the calorimetric glass transition temperature. The various resonances are considerably broadened and partly structured...

In the central part (Sect. 3), the simulation technique will be explained in detail and illustrated by the example of atactic poly(propylene) (Sects. 3.1-3.3). Special sections are devoted to the simulation of the solid state spectrum (Sect. 3.4), the correlation of chemical shift and geometry (Sect. 3.5), a molecular orbital (MO) analysis (Sect. 3.6), the configurational splitting in solution (Sect. 3.7) and the role of the anisotropy of the chemical shift as a source of structural information (Sect. 3.8). 

Fig. 13. Experimental solid state spectrum of atactic poly(propylene) (top) and solution spectrum of configurational splitting in the methylene region (bottom). The broadening in the solid state spectrum is appreciably larger than the configurational splitting. Reprinted with minor changes from [63]...

Method of ab initio Simulation of Solid State NMR Spectra -The Example of Atactic Poly(propylene)... 

In this formula, pconfig is the experimental configurational statistics of the sample to be simulated it is fully determined by the synthetic conditions and is not subject to change. For ideally atactic poly (propylene), the configurational statistics is easily calculated, pco yig( i> 2> 3) = ( ) = 0.125, Xi 6 m, r. I x ) is the conditional conforma-... 

Table 5. Configurational splitting of the methyl carbons in atactic poly (propylene). Because of the small size of the model molecule, only triads can be resolved. The reference for the splitting is the mm configuration...

Experimental spectrum of the methylene region of glassy atactic poly(propylene) (b) recorded atT 240 K on a BRUKER MSL-300 with a DAS probehead. The two angles for evolution and detection, respectively, were =81.7° and = S m = 54.7°. The rotation frequency was 3000 Hz, and 128 fi-increments were recorded. The theoretical values (o) are superimposed on the experimental contour plot. The absolute positions were adjusted like in the ID spectrum. A qualitative agreement of theory and experiment is seen... 

The simulation was based on the 5-state RIS model mainly because it is, at the moment, the best statistical description of atactic poly(propylene). It should be borne in mind, however, that the ab initio simulation technique is not restricted to RIS models. Any model with sufficient predictive power may be used as a basis for the simulation The conformational (or more generally geometric) statistics may be replaced by the results of a molecular dynamics or Monte Carlo study, or any other method. Within computer time limitations, the relevant geometries may be fed into Eq. 3.15 and used as a basis for the quantum chemistry calculations. 

Using the capacity of IGLO to calculate the full chemical shift tensor, first tentative results on the chemical shift anisotropy in atactic poly(propylene) indicate that the tensorial character of the chemical shift may be used as source of structural information, too. 

The method may be used to discriminate between different statistical models by comparing the respective simulation result with experiment (poly(isobutylene)), to check the validity of otherwise established models on a local length scale (atactic poly(propylene)) and to draw conclusions from apparent deviations between experiment and simulation (poly(methyl methacrylate)). 

Kessairi, K., Napolitano, S., Cappacioli, S., Rolla, P., and Wiibbenhorst, M. (2007) Molecular dynamics of atactic poly (propylene) investigated by broadband dielectric spectroscopy. Macromolecules, 40, 1786. 

If the polymer host is structurally constrained from crystallizing, as is the case in atactic poly(propylene oxide) (PPO), the solutions of salts are also amorphous. Quite large concentrations of salt remain dissolved at low temperatures without crystallization occurring. Many conductivity studies have been made on solutions of salts in this polymer, but the conductivities obtained are lower than those obtained for amorphous varieties of PEO, and the range of salts dissolved is more restricted because of the steric hindrance to solvation. Also, steric hindrance to the backbone C—C bond rotation increases compared with the value for PEO. 

Insensitive to changes in crystallinity long chain motion in amorphous portion In atactic poly(propylene) hindered movement of C-CHj units... 

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