Aromatic ring flips in a semicrystalline polymer

Cholli, Ashok L.; Dumais, Joseph J.; Engel, Alan K.; Jelinski, Lynn W.

doi:10.1021/ma00141a032

Cited by 99 publications

(51 citation statements)

References 11 publications

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“…Note that even for C 2 jumps around the C para -C ipso axis, the para deuteron is not being averaged by the motion and should give rise to a static powder pattern. For C-2 H bond in phenyl-rings QCC's of 170-180 kHz (and rj = 0) have been reported by several researchers [11,[36][37][38][39], The 2 H line shapes in solid III are characteristic for phenyl-rings performing C 2 flips around the C para -C ipso axis with a jump angle 20 = 120°. At 290 K the C 2 flips are in the intermediate exchange region, allowing one to obtain a jump correlation time from the line shape.…”

Section: Iv) Reorientational Dynamics Of the -C 6 D 5 Groupmentioning

confidence: 93%

“…In solid I, at 372 K, a 2 H nmr line shape typical for rotational diffusion of a phenyl-ring around the C para -C ipso axis [37,38] was observed. However, if only small angle diffusion around the C para -C ipso axis takes place, the 2 H nmr line shape should consist of an axially symmetric powder pattern with a quadrupolar splitting of 1/8 times that of a static spectrum and an integrated, normalized intensity of 4/5.…”

Section: Iv) Reorientational Dynamics Of the -C 6 D 5 Groupmentioning

confidence: 99%

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Molecular Motion in Phenpropylammonium Chloride Studied by Deuterium NMR

Gruwel

Wasylishen

1992

Zeitschrift Für Naturforschung A

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Cation dynamics in phenpropylammonium chloride, C 6 H 5 (CH 2 ) 3 NH 3 Cr, were studied in three different solid phases by means of 2 H nmr. Both 2 H nmr line shapes and spin-lattice relaxation studies were performed on the ammonium head group, the adjacent methylene group and the phenyl-ring. In the low temperature phase, solid III, the -ND 3 group dynamics were dominated by C 3 jumps about the C-N axis. From the observed minima in T 1Z and T 1Q a quadrupole coupling constant of 165 ± 5 kHz was obtained. The 2 H nmr line shapes of the methylene group indicate that this group does not execute any large amplitude motion in the low temperature phase. In contrast, the phenyl ring deuterium nuclei give rise to line shapes characteristic of C 2 ring flips about the Cpara~C ipso aX * S "In the solid II phase the 2 H nmr line shapes of both the -ND ? and -CD 2 -groups are characterized by asymmetric Pake powder patterns. Since one of the principal components of the electric field gradient tensor remains temperature independent for both groups, it was concluded that these groups perform planar large-amplitude motions between two sites.Axially symmetric spectra were obtained for all three groups in the high temperature phase, solid I. The 2 H nmr line shapes indicate the presence of whole ion reorientation about a molecular axis. In addition, the -ND 3 groups perform C 3 jumps about the C-N axis and the -C 6 D 5 group display line shapes characteristic for rotational diffusion about the C para -C ipso axis.

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Section: Iv) Reorientational Dynamics Of the -C 6 D 5 Groupmentioning

confidence: 93%

Section: Iv) Reorientational Dynamics Of the -C 6 D 5 Groupmentioning

confidence: 99%

Molecular Motion in Phenpropylammonium Chloride Studied by Deuterium NMR

Gruwel

Wasylishen

1992

Zeitschrift Für Naturforschung A

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“…The simulated spectra perfectly reproduced the observed spectra. In order to confirm the acceleration of the rate of the phenylene dynamics of 1-d 4 at temperatures above 270 K, the temperature dependence of the spin -lattice relaxation time (T 1 ) was investigated (24). The relaxation time, T 1 , for the molecular gyrotops was measured using the inversion-recovery quadrupole echo pulse sequence.…”

Section: Resultsmentioning

confidence: 99%

Thermal modulation of birefringence observed in a crystalline molecular gyrotop

Setaka

Yamaguchi

2012

Proc. Natl. Acad. Sci. U.S.A.

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Recently, functional organic materials have been put into practical use. The application of molecular motions has the potential to create new molecule-based materials. For this reason, considerable attention has been focused on the chemistry and properties of molecular machines in which mechanical motions of parts of the molecules are observed. In particular, phenylene rotation in the crystalline state has been investigated using framed molecular gyrotops having a phenylene rotor encased in three long alkyl spokes. In this study, we show thermal modulation of birefringence in a crystal due to the states of dynamic equilibrium of a novel molecular gyrotop. A macrocage molecule having a bridged phenylene rotor was synthesized as a novel molecular gyrotop. Rapid rotation of the phenylene rotor of the molecular gyrotop was confirmed by solid-state 2 H NMR spectroscopy that showed changes in the optical properties of a single crystal, i.e., the thermal modulation of birefringence. These results are the first application of the dynamic states in a crystal causing an optical change. These phenomena were also confirmed by control experiments using a molecular gyrotop with a nonrotating xylene rotor. We anticipate our finding to be a starting point for the creation of a new field of material chemistry that will make use of the dynamic states of molecules. molecular design | molecular material | solid-state NMR O rganic materials, such as liquid crystals and organic lightemitting devices, have been put into practical use, and they have improved the lifestyles of people. These functional organic molecules usually contain moieties of planar π-electron systems such as benzene and naphthalene (1). Benzene is one of the simplest aromatic molecules, and due to its planar structure, a strong anisotropy exists in its physical properties between the in-plane and out-of-plane directions. Therefore, an aggregate of oriented π-electron systems such as crystals and liquid crystals shows anisotropy in its physical properties. When the orientation of molecules inside an ordered aggregation can be switched by partial molecular motion, the physical properties may switch between being anisotropic and isotropic, or they may change the direction of anisotropy as observed in the study of functional liquid crystals and so on. In other words, the application of molecular motions inside an ordered aggregate has the potential to create new molecule-based materials. For this reason, considerable attention has been focused on the chemistry of molecular machines (2-9) in which mechanical motions of parts of the molecules are observed. In particular, the chemistry of partial molecular rotations in the crystalline state has been investigated using molecules that consist of rotors and stators (2,(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Macrocyclic molecules having a rotor encased in a three-spoke stator are expected to have the functions of gyroscopes and compasses in the crystalline state; such molecules were reported as molecular g...

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“…Recently, such a motion has been proposed for. polymers containing aromatic groups in the main chain such as polycarbonate/0 poly(butylene terephtharate) 11 and poly(arylene ether sulfones) 12 on the basis of solid state 2 H and 13 C NMR studies. It has been found that the phenyl ring flip motions are relatively slow.…”

Section: Phb/pet Copolyestermentioning

confidence: 99%

Proton NMR Relaxation Study of Thermotropic Copolyesters

Sato

Suzuki

Inaba

et al. 1987

Polym J

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ABSTRACT:p-Hydroxybenzoic acidlpoly(ethylene terephtharate) (PHB/PET) anrl p-hydroxybenzoic acidl6-hydroxy-2-naphthoic acid (PHB/PHN) thermotropic copolyesters were investigated in the temperature range from -120 to 180°C by observing the proton magnetic relaxation times T1, T1P, and the line width. In the temperature dependence of T1P of PHBIPET two minima of the relaxation times were observed. The one at higher temperature corresponds to the glass transition, and the other at lower temperature ( 40oC) is considered to result from the phenylene group motion. For PHBIPHN, the transition similar to the low temperature one of PHB/PET was observed. The transition temperature of PHB/PHN is higher by 30--40oC as compared with PHB/PET due to the rigid structure. From analysis of line width, it was found that there are two motional regions for both copolyesters, and the activation energies could be obtained. The T1 minimum associated with the glass transition was observed in the T1 experiment. The mesophase formation seems to narrow the distribution of the correlation times of motion.KEY WORDS Liquid Crystalline Polymer I Molecular. Motion I 1 H Nuclear Magnetic Relaxation I Thermotropic Copolyester I Recently, much attention has been focused upon thermotropic copolyesters which provide a potential for developing high modulus materials. Since the pioneering work of Jackson and Kuhfuss 1 was reported, there have been many activities in the synthesis of thermotropic main chain copolyesters. Physical properties of their copolyesters have been investigated in most cases by thermal analysis and morphological observations. 2 To understand the high dynamic modulus resulting from self-reinforcing property of such thermotropic copolyesters, it is essential to investigate the effect of liquid crystal formation on molecular motions. The molecular motion and relaxation have been studied by dielectric dispersion, 3 ESR spin probe, 4 and broad line NMR 5 etc. However, information is limited, and further study is needed. We investigated thermotropic copolyesters by observing 1 H NMR relaxation times, T 1 , T1P, and T2 in the temperature range from -120 to 180°C. Copolyesters studied were p-hydroxybenzoic acid/poly(ethylene terephtharate) (PHB/PET), and p-hydroxybenzoic acid/6-hydroxy-2-naphthoic acid (PHB/PHN) copolyesters. The mole fractions of PHB in PHB/PET copolyester were 30, 60, and 80%. PHB/PHN copolyester contains 73 mol% PHB. These copolyesters are, hereafter, denoted by PHB/PET30, PHB/ PET60, PHB/PET80, and PHB/PHN, respectively. These copolyesters except PHB/PET30 are known to show nematic liquid crystalline behavior. We reported the quite high orientational order of the mesogen in the fiber and film of PHB/PET60 by observing the proton dipolar splitting. 6 In addition to knowledge about the molecular orientation, information concerning the molecular motion is expected to give insight into the nature of liquid crystalline copolyesters. 815

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Aromatic ring flips in a semicrystalline polymer

Cited by 99 publications

References 11 publications

Molecular Motion in Phenpropylammonium Chloride Studied by Deuterium NMR

Molecular Motion in Phenpropylammonium Chloride Studied by Deuterium NMR

Thermal modulation of birefringence observed in a crystalline molecular gyrotop

Proton NMR Relaxation Study of Thermotropic Copolyesters

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