Dipole moments and Kerr constants of dibenzoates of some diols with different numbers of methylene units as model compounds for polyesters

Abstract

Dipole moments and Kerr constants of dibenzoates of several diols have been measured at 25 °C. The general structure of these compounds can be represented as C6H5COO(CH2)mOOCC6H5 with m = 2-6. Dipole moments were obtained from determinations of dielectric constants and refractive indices in benzene solutions. The experimental results for the mean square dipole moments were (µ2) = 7.58, 6.71, 7.20, 7.43, and 7.74 D2 for m = 2, 3, 4, 5, and 6 respectively. Kerr constants were evaluated from measurements of electric birefringence of solutions in cyclohexane (nearly isotropically polarizable solvent); experimental vsdues obtained for m = 2, 3, 4, 5, and 6 were respectively mK = 29.1, 6.9,11.6, 9.4, and 12.3 all in 10~25 m6 V-2 mol-1. Theoretical analysis was performed with standard method of the rotational isomeric states model. Comparison of theory with experiment indicates that (µ2) is almost insensitive to the conformational energies, particularly for m > 3; in fact, the free rotating model gives a reasonably good account for (µ2) for all of these molecules. Kerr constants are much more sensitive to the conformational energies. Good agreement between theoretical and experimental values of both dipole moments and Kerr constants of all these compounds is achieved by adjustment of the optical parameters and the position of the rotational isomers.

Influence of Weak Attractive Interactions on Structures and Properties of Poly(trimethylene terephthalate)

“…Accordingly, the dipole moments and polarizabilities obtained from the MO calculations atthe B3LYP/6-311+G(2d, p) level were employed as they are under conditions of μ x = μ X , μ y = μ Y , μ z = μ Z , α x = α XX , α y = α YY , and α z = α ZZ . Substitution of the μvectors (Table S1), α tensors (Table S2), and Δ G k (MP2) energies (benzene, 25 °C, Table ) into eqs − yielded ⟨ m K ⟩ = 7.04 × 10 −25 m 5 V −2 mol −1 and ⟨μ⟩ = 2.59 D. These results exactly agree with the experimental values, ⟨ m K ⟩ = 6.9 ± 3.9 × 10 −25 m 5 V −2 mol −1 and ⟨μ 2 ⟩ 1/2 = 2.59 D.…”

“…b The cis-trans energy difference around the virtual bond, evaluated from dimethyl terephthalate (Figure 1c). See ref 2. the experimental values, 14 AE m K ae=6.9 ( 3.9 Â 10 -25 m 5 V -2 mol -1 and AEμ 2 ae 1/2 =2.59 D.…”

“…Molar Kerr Constant. Mendicuti et al 14 measured the dipole moment of TMGDB dissolved in benzene at 25 °C and the molar Kerr constant of its cyclohexane solution at 25 °C. We attempted to reproduce the experimental dipole moment and molar Kerr constant of TMGDB from the conformer free energies, dipole moments, and polarizabilities that our MO calculations yielded.…”

Molecular dynamics analysis of the dipole moment and conformational properties of 2-(acetyloxy)ethyl-2-(2-naphthyl)acetate

“…Our results indicate that trans is the preferred orientation for the O᎐CH 2 bonds, while CH 2 ᎐CH 2 prefers gauche, as was found before in the analysis of similar compounds employing a different procedure. 27 It is interesting to notice that in the present calculation the preference of bonds OCH 2 ᎐CH 2 O for gauche states is not introduced a posteriori by means of a socalled gauche effect that has been invoked many times for the analysis of polyoxides. 21 The reason is that the Amber force field contains a better parametrization of this kind of bond, mainly as regards the intrinsic rotational barrier.…”

Coil extension stage in the cold drawing of glassy polymers

“…In our calculations, we still need the conformational energy and the defined energy matrices for the RIS model. The defined RIS energy matrices or vectors for the six bonds12, 14 are as follows: where the element of the matrices is the conformational energy (kJ/mol) for the corresponding RIS. The column before the matrix gives the dihedral angles of the RIS for the preceding bond, and the row above the matrix gives the dihedral angles of the RIS for this bond.…”