Structural studies of polyethers, [‐(CH2)m‐O‐]n. III1. Molecular and crystal structure of polytetrahydrofuran

Imada, Kenjiro; Miyakawa, Takaharu; Chatani, Yôzô; Tadokoro, Hiroyuki; Murahashi, Shunsuke

doi:10.1002/macp.1965.020830109

Cited by 108 publications

(39 citation statements)

References 7 publications

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“…The calculated second moment, however, explains qualitatively the angular dependences of the observed moments. It is concluded that in the rolled PTHF the crystal orients doubly: the (100) plane to which the zig-zag plane of the molecule is parallel orients preferentially parallel to the sheet plane, which is in agreement with the Xray results by Imada, et al 10 …”

Section: Rolled Pthfsupporting

confidence: 81%

“…It was assumed in this calculation that the crystals are uniaxially oriented completely and that the molecules are in the rigid state. The positions of protons in the molecule were determined from the X-ray results by Imada, et al 10 The parameters A1, A 2 , and A3 also depend on the crystal dimensions. The lattice constants of the PTHF crystal are reported to be a=5.59, b=8.73, and c=l2.07 A at room temperature.…”

Section: Drawn Pthfmentioning

confidence: 99%

“…The lattice constants of the PTHF crystal are reported to be a=5.59, b=8.73, and c=l2.07 A at room temperature. 10 To determine the dimensions of the crystal lattice at low temperatures, the interplanar distances of the (130), (110), and (020) reflection planes were measured with changing temperature. It was found that a increases remarkably with increasing temperature from -130°C, but the others do not change appreciably.…”

Section: Drawn Pthfmentioning

confidence: 99%

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Nuclear Magnetic Resonance of Oriented Poly(tetrahydrofuran)

Tsutsumi

Hikichi

Kaneko

1976

Polym J

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ABSTRACT:Wide-line NMR studies of poly(tetrahydrofuran) (PTHF) have been made on drawn and rolled sheets in the range of temperature from -196 to 37°C. The NMR spectra showed pronounced anisotropy with variation of the arrangement of the PTHF sheet in the applied magnetic field. The second moments of the NMR spectra for drawn and rolled sheets were well explained by the uniaxial and double orientations of the crystallites in the sheet. In the rolled sheet, the (100) plane of crystal, to which the zig-zag plane of the molecule is parallel, was found to be oriented preferentially parallel to the sheet plane. A reduction in the second moments of the crystalline regions with increasing temperature was interpreted in terms of the molecular motion in the crystal. A theoretical calculation showed that such a motion involves a rotational oscillation around the molecular axis.KEY WORDS Poly(tetrahydrofuran) / NMR / Sheets / Second Moment / Molecular Motion / Crystal / The molecular motion of poly(tetrahydrofuran) (PTHF) has been studied by dynamic mechanical, dielectric, and nuclear magnetic resonance (NMR) measurements. 1 -4 Willbourn 1 and Wetton and Allen 2 have observed two mechanical relaxations at temperatures below 0°C, which were denoted as (,-and r-relaxations in descending temperature order. In the same temperature region, Wetton and Williams" have found two dielectric relaxations. These relaxations have been interpreted in terms of segmental motion in the amorphous regions. We have carried out NMR measurements and found that PTHF molecules undergo molecular motion in the crystal. 4 The details of such a motion, however, have not yet been clarified sufficiently.In this work, we attempted to examine the molecular motion in the PTHF crystal in more detail. NMR measurements were carried out for drawn and rolled sheets of PTHF. EXPERIMENTAL PTHF with a viscosity average molecular weight of 5 x 10 4 was kindly supplied by Professor Miyake of Hokkaido University. Sheets of 0.5 mm in thickness were cast from concentrated benzene solution at a temperature of 20°C. They were annealed at a temperature of 32°C for a week. Strips cut out from these sheets were drawn slowly in one direction at room temperature up to six times the original length. X-ray photographs of these drawn sheets showed a good orientation of the crystallites along the drawn direction. Some of the drawn sheets were rolled along the drawn direction at room temperature.The drawn and rolled sheets were cut in a rectangular form and then packed parallel to one another in glass tubes for the NMR measurements.The arrangement of samples in the magnetic field is shown in Figure 1. The direction of the magnetic field H0 is specified by the angles w and ¢ in the coordinate system XYZ fixed in the sheet. The YZ plane is parallel to the sheet z X y Figure 1. Direction of the NMR magnetic field with respect to the system XYZ fixed in the sheet (see text). 443

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Section: Rolled Pthfsupporting

confidence: 81%

Section: Drawn Pthfmentioning

confidence: 99%

Section: Drawn Pthfmentioning

confidence: 99%

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Nuclear Magnetic Resonance of Oriented Poly(tetrahydrofuran)

Tsutsumi

Hikichi

Kaneko

1976

Polym J

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“…From the structural studies it is known that PTHF takes an all trans zig-zag conformation in the crystalline regions [15,16]. The appearance of the band at 995 cm -~ indicates that the polymer chain in the complex takes the same conformation as in crystallized samples of PTHE This band is not observed in totally amorphous films of the polymer [17].…”

Section: Ir-spectramentioning

confidence: 99%

Preparation of urea-poly(tetrahydrofuran) complexes and their application for fractionation of oligomers

Schmidt

Enkelmann

Westphal

et al. 1985

Colloid & Polymer Sci

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Abstract:The synthesis of the urea channel inclusion complexes of poly(tetrahydrofuran) 3) (PTHF) is described. These complexes could be obtained in the form of single crystals for Mn < 1700 g/tool of PTHF as the guest, and they exhibit a hexagonal unit cell (a = 8.20(2) it, c= 11.05(3) A) very similar to the wellknown urea-n-alkane complexes. X-ray investigations, elemental analysis and density measurements suggest an all trans zig-zag conformation of the polymer chain.The formation of the complexes was exploited for the purpose of fractionation of PTHF, making use of the correlation between temperature of crystallization and M. of the included polyether chain.The distribution and the molecular weights of the fractions, obtained by extractive crystallization, were determined by reversed phase HPLC analysis and vapour pressure osmometry (VPO). Narrow fractions with MwJMn = 1.02 were obtained from commercial PTHF samples.Successive fractionation was applied also on product mixtures from otigomer synthesis, as demonstrated for the separation of the dodecamer H-(o -(CH2)4 -)12OH.

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“…l3 Assuming that a suitably non-nucleophilic counter ion is present, then the primary requirement for the polymerization of THF is that a tertiary oxonium ion is formed. The latter may be produced in a number of ways: (a) direct acylation14 or alkylation of the heteroatom (b) in situ combination with Lewis acids; [15][16][17] (c) addition of strong protic acids to THF: the addition of a proton to THF results in the formation of the intermediate secondary oxonium ion, which is a comparatively unreactive species, and its slow conversion to the reactive tertiary ion accounts for the relatively slow initiation of the polymerization of THF by protic species. Once the tertiary THF oxonium ion is formed, propagation takes place as a result of bimolecular collisions between THF and this oxonium ion.…”

Section: Mechanism Of Radical Formation and Polymerizationmentioning

confidence: 99%

An ESR study of the polymerization of tetrahydrofuran with simple inorganic cations containing sulphur and nitrogen

Fairhurst

Hulme-Lowe

Johnson

et al. 1985

Magnetic Reson in Chemistry

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The cations of NS,+.AsF,-, N(SCl),+.AsF,-and NS+.AsF,-have been shown to be efficient initiators for the polymerization of tetrahydrofuran. The former two salts were found, by electron spin resonance spectroscopy, to produce remarkably high concentrations of persistent free radicals which have been identified as being entirely inorganic, namely N,S," and, more tentatively, N2&+'. A mechanism for generation of the radicals is proposed.~

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Structural studies of polyethers, [‐(CH₂)_m‐O‐]_n. III¹. Molecular and crystal structure of polytetrahydrofuran

Cited by 108 publications

References 7 publications

Nuclear Magnetic Resonance of Oriented Poly(tetrahydrofuran)

Nuclear Magnetic Resonance of Oriented Poly(tetrahydrofuran)

Preparation of urea-poly(tetrahydrofuran) complexes and their application for fractionation of oligomers

An ESR study of the polymerization of tetrahydrofuran with simple inorganic cations containing sulphur and nitrogen

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