Direction of the dipole moment in the ester group

Sáiz, Enrique; Hummel, John P.; Flory, Paul J.; Plavšić, Marta

doi:10.1021/j150622a002

Cited by 97 publications

(90 citation statements)

References 3 publications

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“…(2) gives 4.8 Debye (1 D ¼ 3.336 Â 10 À30 As m) for the rigid main chain polymer 2 and 18.4 D for both 4 and 6 at 220 K. The estimated dipole value for 4 and 6 is too high to be accounted for only by an ester group relaxation. The magnitude of the dipole moment of the ester group is in the range 1.65e1.80 D [49,50], which is closer to the estimated values of polymer 2 than for 4 and 6. With the side chain attached at R 1 , phenyl ring mobility is hindered.…”

Section: The B-processsupporting

confidence: 66%

Molecular dynamics in semifluorinated side-chain polyesters as studied by broadband dielectric spectroscopy

Tsuwi¹,

Hartmann²,

Kremer³

et al. 2006

Polymer

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Section: The B-processsupporting

confidence: 66%

Molecular dynamics in semifluorinated side-chain polyesters as studied by broadband dielectric spectroscopy

Tsuwi¹,

Hartmann²,

Kremer³

et al. 2006

Polymer

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“…3, 1983 However, it has been shown by measurement of dipole moment that both cis and trans forms are likely to exist in the liquid state of PET. 5 3 Also, Saiz et a/., 54 from a consideration of Coulombic interactions between ester groups ofDMT, concluded that the statistical weight of the cis form is 0.92 relative to the trans form. Moreover, Lowe et a/.…”

mentioning

confidence: 99%

Anisotropic Absorption and Reflection Spectra of Poly(ethylene terephthalate) Films in Ultraviolet Region

Ouchi

1983

Polym J

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ABSTRACT:Thin uniaxially drawn poly( ethylene terephthalate) films (down to 0.1 flm thickness) were prepared. Their absorption spectra showed clear dichroism having peaks at 300 (.l), 243 (/ /) and 197 nm (/ 1). Analysis of the reflection spectra of thick films by means of the Kramers-Kronig conversion gave absorption spectra almost identical with those obtained from direct absorption measurement. Spectral shapes and possible origins of the vibrational structures were qualitatively discussed. The oscillator strength of each band was obtained on the simple oriented gas model with or without the Lorentz field correction to examine effects of molecular aggregation. PPP calculations with CI were made by use of a model compound, and four 1 A•-> 1 Bu allowed transitions were predicted to occur at 4.66, 5.27, 6.33 and 6.44eV. The latter two transitions were actually observed at 6.2eV. The calculated transition moments suggested the existence of the cis form of carbonyl groups in oriented amorphous phases.

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“…This is in agreement with the previous studies employing coulombicenergy calculations. [17] For (f 2 , f 3 ), the energy barrier for the transition between two minima is found to be 5.24 kcal Á mol À1 . The rotational states corresponding to f 5 (f 7 ) are 5 and 958, with the former torsional state at a slightly higher energy value by 0.16 kcal Á mol À1 .…”

Section: Ris Model For Cbdomentioning

confidence: 93%

“…Flory and coworkers have reported that the sterically favored conformations for the dimethyl trans-cyclohexane-1,4-dicarboxylate molecule is one in which the ester groups are coplanar with the axial C-H bonds. [17] Since the cyclohexylenedicarboxylate linkage is in the trans configuration, the torsional value at the f 3 bond is 08. Statistical weight matrices for the bonds relating to the cyclohexanedimethanol fragment are similar to those of PCT, where the trans and cis configurations of the cyclohexanedimethanol group are included (Figure 3).…”

Section: Ris Model For Pccmentioning

confidence: 99%

RIS Models and Unperturbed Chain Properties of Polyesters Containing 1,3‐Cyclobutylene and 1,4‐Cyclohexylene Linkages

Sulatha

Natarajan

2003

Macro Theory & Simulations

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Polyesters containing 1,3‐cyclobutylene and 1,4‐cyclohexylene linkages in the main chain are investigated using conformational energy calculations. Rotational isomeric state (RIS) models are developed for poly(1,4‐cyclohexylenedimethylene terephthalate) (PCT), poly(1,4‐cyclohexylenedimethylene 2,5‐dimethylterephthalate) (DMPCT), poly(1,4‐cyclohexylenedimethylene 1,4‐cyclohexylenedicarboxylate) (PCC), and poly(2,2,4,4‐tetramethyl‐1,3‐cyclobutylene terephthalate) (CBDO). In DMPCT, the ester linkage prefers skewed conformations with respect to the phenyl group to relieve the steric strain caused by the methyl groups. The methyl groups on the cyclobutanediol moiety in CBDO restrict the rotational freedom about the oxycyclobutylene linkage. The unperturbed dimensions as described by characteristic ratio and persistence length are calculated for the trans and cis configurations of these polyesters. CBDO shows highly extended chain conformations among these polyesters indicating relative chain rigidity of the backbone. For DMPCT and PCC, in their trans configuration, the chain dimensions decrease with an increase in temperature while for their cis configurations, the chain dimensions increase with temperature, arising from basic differences in the fragment structures that control the competition of the relative populations as affected by temperature. Temperature has negligible influence on the unperturbed dimensions of both isomeric linkages of CBDO, while this is true for the trans configuration of PCT. The study shows that induction of cyclobutylene groups in the main chain results in a greater rigidity for homopolyesters than for chains with cyclohexylene groups.

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Direction of the dipole moment in the ester group

Cited by 97 publications

References 3 publications

Molecular dynamics in semifluorinated side-chain polyesters as studied by broadband dielectric spectroscopy

Molecular dynamics in semifluorinated side-chain polyesters as studied by broadband dielectric spectroscopy

Anisotropic Absorption and Reflection Spectra of Poly(ethylene terephthalate) Films in Ultraviolet Region

RIS Models and Unperturbed Chain Properties of Polyesters Containing 1,3‐Cyclobutylene and 1,4‐Cyclohexylene Linkages

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