Structure of a new crystalline phase of syndiotactic polypropylene

Chatani, Yôzô; Maruyama, Hiroyoshi; Asanuma, Tadashi; Shiomura, Tetsunosuke

doi:10.1002/polb.1991.090291310

Cited by 160 publications

(181 citation statements)

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“…The chemical shift difference among each peak in the methylene region is represented as yCH-CH 2 , the difference between two peaks in the methine region is (yCH 2 -CH)-(yCH 3 -CH), and the difference between two peaks in the methyl region is yCH-CH 3 • The observed values in the spectrum of sample C were 4.3 ppm, 0.5 ppm, and 3.2 ppm, respectively. Chatani et al 20 reported a new structure of s-PP by X-ray structure analysis. The s-PP sample with planar zigzag form was exposed to benzene, toluene, or p-xylene vapor below 50°C for several days.…”

Section: Structure Determination Of New Form IIImentioning

confidence: 99%

High Resolution Solid State 13C NMR Spectroscopy of Polypropylene with Very High Syndiospecificity

Asakura

Aoki

Date

et al. 1996

Polym J

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ABSTRACT:The high resolution solid state 13 C NMR spectra were observed for highly syndiotactic polypropylene samples with three kinds of crystalline forms, forms I, II, and III. The forms I and II are the most stable helical conformation, (-TTGG-), and all trans planar zigzag conformation, respectively. The sample with the third new crystalline form, form Ill, was prepared by soaking the sample with form II in toluene at room temperature for two days. The conformation was proposed to be (-T 6 G2 T2 G2-). This is based on the comparison of the observed spectrum with the calculated ones with 13 C NMR y-effect for the candidates of the conformation. There are form I (23%) and amorphous component (I 1 %) other than form III (66%) in the sample at 20°C. From the variable temperature NMR experiments of these three samples with predominantly forms I, II, and III, respectively, the transitions among different crystalline forms and amorphous component were discussed.KEY WORDS Highly Syndiotactic Polypropylene/ High Resolution Solid State 13 C NM R Spectroscopy/ 13 C y Shielding Effect/ Crystalline and Amorphous Components/ (-T6 G2 T 2 G2-) Form of Syndiotactic Polypropylene / Contrary to isotactic polypropylene (i-PP), syndiotactic polypropylene (s-PP) has recieved very little attention. This is due to the poor syndiospecificity of the earlier catalysts. However, in the last few years, new metallocene catalysts have been developed, which allow very high syndiospecificity. 1 • 2 Thus, a detailed structural study of such a highly stereoregular s-PP will be necessary.Two different crystalline forms 3 -7 of the chains have been reported for s-PP obtained by changing the preparations of s-PP samples. One form is called form I which consists of chains with (-TTGG-)i conformation, and another is form II with planar zigzag conformation. Form I is the most stable structure in s-PP, while form II undergoes a transition to form I above 50°C with increasing temperature. 6 The structures of form I and of the sample after drawing have already been studied by Bunn et al. 7 and Sozzani et al. 8 • 9 by using solid-state 13 C NMR. These NMR spectra were interpreted in terms of preferred conformations and the y-effect on the 13 C NMR chemical shift. 10 • 11 In this study, a sample with predominantly new crystalline form, form III, was obtained by special sample preparation. The 13 C CP/MAS NMR spectrum was significantly different from those of other forms, forms I and II. The differences in the spectra among three forms, I, II, and III were interpreted by taking into account of the preferred conformations and the 13 C NMR y-effect. Then the conformation of the new crystalline form, form III, was proposed. Moreover, the transition among three crystalline forms and amorphous component was examined from the temperaturedependent 13 C CP/MAS NMR spectra of three samples and then the determination of the fraction of each form t To whom correspondence should be addressed. tt Present address: Plastic Laboratory, Tokuyama Co., 1-1 Harumicho, To...

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Section: Structure Determination Of New Form IIImentioning

confidence: 99%

High Resolution Solid State 13C NMR Spectroscopy of Polypropylene with Very High Syndiospecificity

Asakura

Aoki

Date

et al. 1996

Polym J

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“…A different form (Form III) can be obtained by stretching the compression moulded samples or by crystallization at 0 8C 7,12) , and it is characterised by chains in zigzag planar conformation. Form IV was obtained by Chatani et al 8) by exposing fibre specimens in the zigzag conformation to organic solvents. It is characterised by helices in a (T 6 G 2 T 2 G 2 ) n conformation, packed in a triclinic cell.…”

Section: Introductionmentioning

confidence: 99%

Correlation between crystallinity and some infrared bands in the spectra of syndiotactic poly(propylene)

Guadagno

D’Arienzo

Vittoria³

2000

Macromol. Chem. Phys.

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“…To date, four limit-ordered crystalline modifications of s-PP were proposed and described in the literature. [55][56][57][58][59][60][61][62][63][64][65][66][67][68][69] Of the four crystalline forms, only the molecular chain packing models of the limitordered form I 56 -59,64,66 and the limit-disordered form I 59,63,66 (after the most recent nomenclature given by De Rosa et al 70 ) are appropriate for characterizing s-PP samples that are crystallized under quiescent conditions from the melt state (or from solution).…”

Section: Dependence Of Subsequent Melting Endotherms On Crystallizatimentioning

confidence: 99%

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Supaphol

2001

J of Applied Polymer Sci

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ABSTRACT:The melting behavior of syndiotactic polypropylene (s-PP) after isothermal crystallization from the melt state was studied using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) techniques. Three melting endotherms were observed for isothermal crystallization at high degrees of undercooling. The minor endotherm, located closed to the corresponding crystallization temperature, was postulated to be the melting of the secondary crystallites formed at the crystallization temperature. The low-temperature melting peak was found to be the melting of the primary crystallites formed, and the high-temperature melting peak was a result of the melting of the crystallites recrystallized during a heating scan. The triple-melting behavior observed in subsequent melting endotherms of s-PP was therefore described as contributions from melting of the secondary crystallites and their recrystallization, partial melting of the less stable fraction of the primary crystallites and their recrystallization, melting of the primary crystallites, and remelting of the recrystallized crystallites formed during the heating scan. In addition, determination of the equilibrium melting temperature for this s-PP resin according to the linear and nonlinear Hoffman-Weeks extrapolations provided values of 143.1 and 185.6°C, respectively.

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Structure of a new crystalline phase of syndiotactic polypropylene

Cited by 160 publications

References 7 publications

High Resolution Solid State 13C NMR Spectroscopy of Polypropylene with Very High Syndiospecificity

High Resolution Solid State 13C NMR Spectroscopy of Polypropylene with Very High Syndiospecificity

Correlation between crystallinity and some infrared bands in the spectra of syndiotactic poly(propylene)

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

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