Polypropylene, deuterated

Polarized infrared spectra of oriented specimens of isotactic polypropylene are shown in Fig. 14 [Peraldo (167)]. The band positions, polarizations, and relative intensities are given in Table 14, together with Raman data [Tobin 231)] and information on the phase of origin of the bands [Natta [149) Pokrovsky and Volken-shtein 178) Abe and Yanagisawa (/)]. Some preliminary data on partially deuterated polypropylenes are available [Peraldo 167) Natta 130)], but no detailed spectra have as yet been published. 

It will be apparent from the above discussion that a satisfactory set of assignments has not yet been achieved for the polypropylene spectrum. In most cases this is because the basic nature of the mode is unknown. Studies on partially and fully deuterated polypropylenes would answer these questions, and will clearly have to be undertaken in order for the final results to be more certain. When this has been done it should then be possible to evaluate more meaningfully the significance of the deviations between the observed and calculated I Ie ratios. As we have noted, these ratios are determined by the structure, if we make simple assumptions about the group transition moment directions. The deviations imply that either these assumptions are not valid or that the structure requires... 

Drawn isotactic polypropylene (iPP) fibres have been studied by using deuterated n-decane as a 2H NMR probe of the chain deformation ratio in the amorphous regions. It is observed that the slope P=A/(X2-X 1) (defined in the limit of low deformations) indeed depends on the annealing temperature [82]. Thus, annealing above the melting temperature Tm of the crystallites allows chains to relax to some extent. Then, the local deformation ratio in the amorphous phase Xt becomes lower than the macroscopic one X and depends on the annealing temperature, i.e., on the amount of chain relaxation. Therefore, such systems have strongly non-affine deformation at the chain scale. 

Two examples are shown in Figs. 25 and 26, where Qc and Ojlhrij are plotted as a function of 2. In the first case we compare interfaces between an epoxy and either PS or high-impact PS, where both interfaces have been reinforced with the same deuterated end-grafted chain, while, in the second case, we compare interfaces between polyamide 6 (PA-6) and either polypropylene (PP) or a PP-based alloy with a PP matrix and 70% EPDM rubber particles, where both interfaces have been reinforced with the same type of grafted PP chains. Two observations can be made ... 

Temperature dependence of x for mixtures of polyisobutylene and deuterated head-to-head polypropylene and the calculated phase diagram from Flory-Huggins theory with... 

R. G. Snyder J.H. Schachtschneider (1964). Spectrochim. Acta, 20, 853-8610. Valence force calculation of the vibrational spectra of crystalline isotactic polypropylene and some deuterated polypropylenes. 

Figure 2.9. Temperature dependence of the binary interaction parameter, X12 blends of deuterated amorphous polypropylene (either head-to-tail or head-to-head, hh) with polyethylene copolymers. The values were determined by SANS. Data [Graessley etal, 1995].

Fig. 9.25 A static exchange experiment recorded for a sample of methyl-deuterated isotactic polypropylene (iPP) at T = 387 K. The observed elliptical ridges are characteristic of...

Notes The values of A, B, and C and thus of y are based on a reference volume Vre/ = 0.1 nm Polymer notation A d- label preceding the polymer acronym indicates a per-deuterated polymer partially deuterated polymers are labeled as dy, df, etc., for selective deuteration of 3, 4, etc., hydrogens. Numbers in subscripted parentheses after the polymer name indicate the primary comonomer fraction, e.g., SPB(6s) is a saturated polybutadiene with 66 mol% butadiene Polymer acronyms P2VP poly(2-vinyl pyridine), P4MS poly(4-methylstyrene), PBMA poly(n-butyl methacrylate), PCHA poly(cyclohexyl acrylate), PEB poly(ethyl butylene), PIB polyisobutylene, PI polyisoprene, PMMA poly(methyl methacrylate), PPMA poly(n-pentyl methacrylate), PP polypropylene, HHPP head-to-head polypropylene, PS polystyrene, PVME poly(vinyl methyl ether), PXE poly(2,6-dimethyl-l,4-phenylene oxide), SPB saturated polybutadiene, SPI saturated polyisoprene... 

Both polypropylene and poly(2-fi(i-propylene) displayed similar tacticities (r = 83.3% and 84.2%, respectively), but the deuterated monomer produced higher molecular weight polymer (Mn 32,840 versus 56,830, respectively). Based on these molecular weights, a k(f)-H)/k(f)-D) value of 1.6 can be calculated, suggesting that P-H elimination is the predominant chain termination pathway. This result is consistent with the expectation that P-H elimination would be slower for the polymerization of 2-di-propylene than for polypropylene. 

Stehling and Knox [5, 16] defined the stereochemical structure of PP from the PMR spectrum of normal deuterated and epimerised polypropylene. 

A majority of the data collected using this cell has been with a polypropylene (PP) - polyethylene (PE) system, using a combination of two PP tacticities and a number of PE s of varying densities from linear low density PE (LLDPE) to high density PE (HOPE) [18,20,21], Deuterated isotactic PP (diPP) is semi ciystalline with a melt temperature of 157 C, while deuterated atactic PP (daPP) is amorphous. The melt temperatures of the LLDPE and HDPE used are 102 and 131 C, respectively. Reflectivity profiles from all the systems were obtained at temperatures well above the melt and ass transition temperatures of the polymers. Data from the diPP-HDPE system have been collected at 175, 200 and 225 C and the interfhcial widths obtained. The fitting revealed that in some cases the diPP does not folly wet the silicon [21], but the diPP layer was sufficiently thick to prevent complete dewetting... 

A number of recent papers describe the use of high resolution NMR spectroscopy in identifying stereosequence distribution in polypropylene oxide (9-11,17-20). Using o -deuterated polypropylene oxide and 220 HMz NMR, Ogunl et al (19) have shown that the shift in methylene absorbtion can be used to identify the structures assigned to tail-to-tail linkages and to isotactic and syndiotactic triads. They showed that the crystalline fraction of polymer prepared with a dlethyl-zinc-water catalyst system did not contain a measurable amount of tail-to-tail linkages. 

Coupled HPLC-NMR measurements performed at slow flow rates in fully deuterated solvents and at room temperature have been made in several studies to determine polymer MWD, to analyze the end-groups and the copolymer chemical composition distribution, and to assess the chemical structure and the degree of polymerization of all oligomer species [176-178]. Gradient HPLC-NMR was used in the analysis of the chemical composition distribution of random poly (styrene-co-ethyl acrylate) copolymers [179]. A major drawback in most of these studies is that the measurements could only be conducted at ambient or slightly elevated temperatures, which limits the method applicability, since many polymers, such as polyethylene, polypropylene, and polyolefin copolymers are soluble at high temperatures. 

Figure 2. PMR Spectra of Partially Deuterated Isotactic Polypropylenes [12,14,15].

Figure 8.28 Ds (right axis) of ( ) 33.6 kDa polypropylene oxide chains in solutions of 32 kDa PPO chains in a 1 kDa PPO melt, based on measurements of Smith, et a/. (45). Ds (left axis) of 255 kDa deuterated polystyrene in mixtures of (O) 93, (0) 250, or ( ) 20 000 kDa polystyrene and molten 10 kDa polystyrene, using measurements by Tead and Kramer(46). Temperatures were 150, 150, and 175 °C, respectively for clarity, the 150" C data have been shifted upward by a factor of 100.

One area where SANS has greatly contributed to the understanding of phase behavior is that of polyolefin blends [75-77]. For these systems, one would expect to measure a positive x value but, contrary to these expectations, SANS experiments have revealed complex thermodynamic interactions of both attractive and repulsive type [75-77]. This is illustrated by the example in Figure 5.10 where the SANS data for a blend of saturated poly(ethylbutadiene) with elevated 3,4 content and deuterated polypropylene, at three different temperatures, are plotted and compared with the predicted intensity for the same blend without interactions (x = 0). The experimental... 

---