Correlation between <sup>13</sup>C NMR Chemical Shifts and Conformation of Polymers. 3. Hexad Sequence Assignments of Methylene Spectra of Polypropylene

Zambelli, Adolfo; Locatelli, Paolo; Provasoli, Augusto; Ferro, Dino R.

doi:10.1021/ma60074a012

Cited by 93 publications

(47 citation statements)

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“…The PP spectrum can be interpreted well from our results calculated for the model compound (NMND) as well as the calculation for atactic PP by TonellP and Zambelli et a/. 6 In the following, attention is focused primarily on the chemical shifts of 13 C NMR spectra of the methylene carbon of the side chain of isotactic PB and the methyl carbon of atactic PP at 100°C. Stick spectra calculated at 100°C at the pentad level for the C10 methylene carbon ofNEND and C10 methyl carbon of NMND appear below.…”

Section: Resultssupporting

confidence: 78%

“…14 Next, -3.7 ppm was taken as the y value for the methine carbons and methyl side chain carbons on the methylene backbone carbons and for the methylene backbone carbons on the methyl side chain carbons in order to reproduce the spread of these carbon chemical shifts, with r* =0.6. The use of different y values depending on the species of carbon atom is also supported by Zambelli et al 6 in the chemical shift calculation of PP.…”

Section: Calculation Ofmentioning

confidence: 71%

“…The chemical shifts were calculated for diastereomers of 2, 4,6,8,10,12,14,16,, in which the methylene C9 and methine C10 of the backbone chain and methylene C10 and methyl C10 of the side chain serve as models of (;H2 (backbone), <;;;H, (;H2 (side chain), and (;H3 of poly(l-butene) (PB), respectively. The so-called y effect and Suter-Flory rotational isomeric model were taken into account in the calculation.…”

Section: Introductionmentioning

confidence: 99%

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The Carbon-13 NMR Chemical Shift of Poly(1-butene) Referring to that of 2,4,6,8,10,12,14,16,18-Nonaethylnonadecane and a Comparison of the Chemical Shifts between Poly(1-butene) and Polypropylene

Asakura

Ômaki

Zhu

et al. 1984

Polym J

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ABSTRACT:The chemical shifts were calculated for diastereomers of 2, 4,6,8,10,12,14,16,, in which the methylene C9 and methine C10 of the backbone chain and methylene C10 and methyl C10 of the side chain serve as models of (;H2 (backbone), <;;;H, (;H2 (side chain), and (;H3 of poly(l-butene) (PB), respectively. The so-called y effect and Suter-Flory rotational isomeric model were taken into account in the calculation. Additional repulsive interaction, r* = 0.6 between the ethyl group of the side chain and backbone was also considered when both adjacent backbone bonds were trims. The y interaction was clarified to be important between the methylene carbons of the backbone chain and methyl carbons of the side chain. The methylene (tetrad) and methine (pentad) carbons of the backbone chain and the methylene (pentad) and methyl (pentad) carbons of the side chain of isotactic "PB were successfully assigned to stereosequences by a comparison with the calculated spectra of NEND. A similar calculation was done for the chemical shifts of the methylene C9 , methine C10, and methyl C 10 of 2, 4,6,8,10,12,14,16,18-nonamethyl The y effect is recognized in 13 C NMR studies of paraffinic hydrocarbons as an upfield shift of ca. -5 ppm in the guache arrangement of carbon atoms separated by three bonds (y substituents) relative to their trans arrangement. 8 -10 The actual magnitude of the y effect should depend on the probability of bond conformation. For the case of PP and corresponding model compounds such a "bond rotation probability" can be calculated using the Suter-Flory rotational isomeric state (RIS) modelY The 13 C NMR chemical shift observed for PP is therefore directly related to its conformational characteristics, (bond rotation probability).In a previous paper, 12 one of the authors reported the 13 C NMR spectrum of isotactic poly(l-butene), (PB) along with the tentative assignment and chain dynamics. The spread of

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Section: Resultssupporting

confidence: 78%

Section: Calculation Ofmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

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The Carbon-13 NMR Chemical Shift of Poly(1-butene) Referring to that of 2,4,6,8,10,12,14,16,18-Nonaethylnonadecane and a Comparison of the Chemical Shifts between Poly(1-butene) and Polypropylene

Asakura

Ômaki

Zhu

et al. 1984

Polym J

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“…4,5,30 It is important to examine both the average microstructures and microstructural distributions of Ziegler-Natta poly(propylenes) in light of their crystallization behavior. Therefore, in a separate part of this work, 31 13 C NMR data will be analyzed utilizing all of the current as well as some newly modified two state and three state statistical models.…”

Section: Introductionmentioning

confidence: 99%

Crystallization Rates of Matched Fractions of MgCl₂-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

et al. 2003

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The microstructures of two poly(propylene)s with matched molar masses and overall defect concentrations are inferred from the crystallization behavior of their narrow molar mass fractions. One poly(propylene) was produced with a MgCl2-supported Ziegler-Natta catalyst and the other with a metallocene catalyst. The fractions obtained from the metallocene isotactic poly(propylene) display a range in molar masses but each has the same defect concentration indicating a uniform intermolecular concentration of defects in the parent metallocene isotactic poly(propylene). These fractions provide direct evidence of the "single site" character of the metallocene catalyst. The variations of crystallization rates with molar mass reflect different chain diffusion/transport phenomena that are governed by the remnant entanglement state of the melt during crystallization. The molar mass fractions obtained from the ZN-iPP confirm that the interchain distribution of the nonisotactic content is broad in this polymer. The stereodefects are more concentrated in the low molar mass fractions. Furthermore, the invariance of the linear growth rates among the ZN fractions and the lack of formation of any significant content of the γ polymorph, even in the most defected fraction, is consistent with a nonrandom, blocky intramolecular distribution of defects in the ZN-iPP molecules. In contrast to the growth rates, the overall crystallization rates are a direct function of the primary nucleation density, which varies among the fractions and the unfractionated iPPs. Hence, the measured overall crystallization rates would be correlated with nucleation density and not necessarily with the microstructure of the iPP molecules. The crystallization data are also interpreted in light of results from pentad/heptad distributions predicted by two-state and threestate statistical models. Parameters from the models allow the prediction of sequence distribution curves that could be used to evaluate each of the models as to their consistency with the crystallization rate data.

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“…Evidence for the self‐correcting propagation would be given by the signal mrrm. The population ratio of the isolated racemic pentads in this case will be around21 The sensitivity of the polymer microstructure to reaction conditions61 can be depicted by an evaluation of the isotactic pentad content [mmmm]. Increasing propylene pressure and decreasing polymerization temperature always increase the isotactic pentad content, probably because of the effect of the monomer concentration on the rate of monomer enchantment at either site of the catalyst, with the rate of catalyst isomerization independent of the monomer concentration.…”

Section: Introductionmentioning

confidence: 99%

Mesoscopic modeling of the polymerization, morphology, and crystallization of stereoblock and stereoregular polypropylenes

Madkour

Mark

2002

J Polym Sci B Polym Phys

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Thermoplastic elastomers require domains that act as physical crosslinks, and these can be either glassy regions or crystallites. For crystallites in a polymer such as polypropylene (PP), the challenge is to develop polymerizations that form the long stereoregular chain sequences required to produce crystallites large enough to act as stable temporary crosslinks but not so many of them that the material becomes a significantly crystalline thermoplastic rather than an elastomer. For PP, the requirement is for long isotactic sequences within predominantly elastomeric atactic chains, and catalysts required to achieve such an unusual stereoblock structure are now available. This provided encouragement for the simulations described herein that illustrate some relationships between polymerization mechanisms and distributions of isotactic sequences (particularly those long enough to crystallize). A Windle‐type Monte Carlo algorithm was then applied to arrays of the representative PP chains in searches for matches of crystallizable sequences. This approach provided estimates of degrees of crystallinity, melting points, interfacial free energies, standard free energies of fusion, and Young's moduli at small extensions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 840–853, 2002

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Correlation between ¹³C NMR Chemical Shifts and Conformation of Polymers. 3. Hexad Sequence Assignments of Methylene Spectra of Polypropylene

Cited by 93 publications

References 1 publication

The Carbon-13 NMR Chemical Shift of Poly(1-butene) Referring to that of 2,4,6,8,10,12,14,16,18-Nonaethylnonadecane and a Comparison of the Chemical Shifts between Poly(1-butene) and Polypropylene

The Carbon-13 NMR Chemical Shift of Poly(1-butene) Referring to that of 2,4,6,8,10,12,14,16,18-Nonaethylnonadecane and a Comparison of the Chemical Shifts between Poly(1-butene) and Polypropylene

Crystallization Rates of Matched Fractions of MgCl₂-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

Mesoscopic modeling of the polymerization, morphology, and crystallization of stereoblock and stereoregular polypropylenes

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Correlation between 13C NMR Chemical Shifts and Conformation of Polymers. 3. Hexad Sequence Assignments of Methylene Spectra of Polypropylene

Cited by 93 publications

References 1 publication

The Carbon-13 NMR Chemical Shift of Poly(1-butene) Referring to that of 2,4,6,8,10,12,14,16,18-Nonaethylnonadecane and a Comparison of the Chemical Shifts between Poly(1-butene) and Polypropylene

The Carbon-13 NMR Chemical Shift of Poly(1-butene) Referring to that of 2,4,6,8,10,12,14,16,18-Nonaethylnonadecane and a Comparison of the Chemical Shifts between Poly(1-butene) and Polypropylene

Crystallization Rates of Matched Fractions of MgCl2-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

Mesoscopic modeling of the polymerization, morphology, and crystallization of stereoblock and stereoregular polypropylenes

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Product

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Correlation between ¹³C NMR Chemical Shifts and Conformation of Polymers. 3. Hexad Sequence Assignments of Methylene Spectra of Polypropylene

Crystallization Rates of Matched Fractions of MgCl₂-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure