Conformational analysis of polyoxyethylene using empirical force field methods

Miyasaka, Tsutomu; Yoshida, Takaichi; Imamura, Yosuke

doi:10.1002/macp.1983.021840619

Cited by 11 publications

(3 citation statements)

References 13 publications

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“…This is illustrated in Figure 2 for the tg±g=F conformer, where the O-C(methyl) and O-H(methyl) separations are 3.15 and 2.57 A, respectively. These are greater distances than found in typical intramolecular hydrogen bonds but are considerably shorter than seen for the other conformers (e.g., 4.70 and 4.90…”

Section: Resultsmentioning

confidence: 58%

“…The present result is significantly lower than the 0.4-0.6 kcal/mol obtained in previous investigations, where an estimate of the 6-31G** energy at the MP4 level was obtained,12 or where MP4(SDQ) calculations were carried out using the 6-31++G* basis set.14•15 However, our result remains well above estimates (-0.4 to -1.2 kcal/mol) based upon the RIS basis set, in Debye. 4 An energy of 0.10 kcal/mol, obtained using the MP2 optimized geometry (see Table I), was used in calculations of conformer populations.…”

Section: Resultsmentioning

confidence: 99%

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Conformation of 1,2-dimethoxyethane from ab initio electronic structure calculations

Jaffe¹,

Smith²,

Yoon³

1993

J. Phys. Chem.

141

192

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The conformational properties of 1 ,Zdimethoxyethane (DME) have been analyzed in detail using ab initio electronic structure calculations in order to better understand the influence of oxygen gauche effects on the conformation energies and populations of DME. Our calculations indicate that the energy of the gauche conformation of the 0-C-C-O bond relative to the trans conformation, which reflects the strength of the oxygen gauche effect in DME, depends strongly not only on the basis set size but also on electron correlation effects. Specifically, the energy of the tgt conformation of DME relative to the ttt conformation was determined for various basis sets at both the SCF and MP2 levels. MP2 level calculations with a D95+(2df,p) basis set, a Dunning double-tbasis set of the form (lOs6p2dlf/4slp)/[5s2p2dlf/2slp], yield an energy ofca. 0.1 kcal/mol for the gauche conformation, as compared with 0.75 kcal/mol for MP2 level calculations with the smaller D95** basis set and 1.0 kcal/mol for SCF level calculations employing the D95+(2df,p) basis set. A salient result of our investigation is the determination that the energy of the tgigF conformation lies only ca. 0.2 kcal/mol above that of the ttt conformation, apparently due to strong 0-H attractions. Finally, we find that the conformer populations of DME obtained from conformational energies determined at the MP2 level with a D95+(2df,p) basis set are in good agreement with those derived from electron diffraction experiments and can be used to successfully reproduce experimental values of N M R vicinal coupling constants and dipole moments for DME.

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Section: Resultsmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 99%

Conformation of 1,2-dimethoxyethane from ab initio electronic structure calculations

Jaffe¹,

Smith²,

Yoon³

1993

J. Phys. Chem.

141

192

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“…Moreover, our separate quantum chemical calculations to check the stability of the g ± g ∓ g ± t conformer of the CH 3 CH 2 OCH 2 CH 2 OCH 3 molecule did not show any such low-energy minimum. In addition, Miyasaka et al previously carried out molecular mechanics calculations on CH 3 CH 2 OCH 2 CH 2 OCH 2 CH 3 molecule and concluded that the conformations containing more than two consecutive gauche states were found to be higher in energy . Therefore, the surprising results of ref indicate that the force fields employed therein are grossly overestimating the electrostatic attractions or underestimating the unfavorable torsional energies or the steric repulsions in the g ± g ∓ g ± CH 2 CH 2 OCH 2 CH 2 O conformations and thus cast doubt on the melt chain results as well.…”

Section: Chain Conformationsmentioning

confidence: 99%

Conformations and Structures of Poly(oxyethylene) Melts from Molecular Dynamics Simulations and Small-Angle Neutron Scattering Experiments

et al. 1996

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An ensemble of H(CH2OCH2)12H chains has been studied by molecular dynamics simulations as both melt chains and unperturbed phantom chains as a model system to investigate condensed phase effects on chain conformations of poly(oxyethylene) (POE). In addition, conformations of high molecular weight POE chains in the melt have been determined by small-angle neutron scattering (SANS) experiments over a temperature range of 347-459 K. Our simulations show that POE chains in the melt are more extended than the phantom chains which represent the unperturbed chains in Θ solution. Moreover, the melt chains exhibit a negative temperature coefficient of chain dimensions in contrast to a positive value for the phantom chains. The difference in chain dimensions and the difference in the temperature dependence of chain dimensions between melt and phantom chains are corroborated by the results of our SANS measurements when they are compared with experimental results for POE chains in Θ solution. We attribute these significant deviations in conformational properties of POE chains in the melt from those of unperturbed ideal chains to condensed phase effects, similar to those found in 1,2-dimethoxyethane (DME), a dimer molecule of POE, from both experiments and simulations. That is, simulations show that the population of the C-C-O gt conformation is greater in melt chains than in the phantom chains, while the C-C-O g ( gpopulations are much smaller in the melt, the latter effect largely accounting for the more extended dimensions of the melt chains. As in DME, the conformationdependent intermolecular polar attractions (O‚‚‚H interactions, for example) account for these condensed phase effects, which become more pronounced at lower temperatures. Such intermolecular polar attractions in POE melts also result in increased interatomic packing order, but do not appear to enhance the intermolecular orientational order when compared to simulation results for polymethylene melts.

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Polyethyleneoxide‐Dynamics in Aqueous Solutions Studied by Nuclear Magnetic Relaxation

Breen

Duijn

Bleijser

et al. 1986

Ber Bunsenges Phys Chem

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The local polymer dynamics of polyethyleneoxide in aqueous solutions were studied by 'H-and '3C-nuclear magnetic relaxation. The concentration dependence is caused by polymer-polymer interactions, whereas in the concentration independent range the polymer dynamics is mainly determined intramolecularly and by water-PEO interactions. The latter interaction is influenced by the presence of salts. MW-dependence of the relaxation rates is not observed for D p > 100. From the dispersion of the 'H relaxation rates, for a PEOsample with Dp = 360 at a concentration of 0.5 mol/kg, the polymer segment dynamics are evaluated in terms of an overall and an internal motion. IntroductionMolecular motions on a time scale in the range between ps and ms can be investigated by nuclear magnetic relaxation. The dynamic behaviour of macromolecules in solution is characterized by correlation times in this range.Nuclear magnetic relaxation is driven by the modulations of local nuclear interactions, e. g. 'H-I3C dipolar coupling and C -D quadrupolar coupling. The chain segment mobility, responsible for the modulation of the coupling, depends on the flexibility of the polymer chain. From previous studies in which correlation times were determined, it is clear that single monomer units are not free to reorient. The problem is then to determine the average size of the chain segment reorientating independently.

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Conformational analysis of polyoxyethylene using empirical force field methods

Cited by 11 publications

References 13 publications

Conformation of 1,2-dimethoxyethane from ab initio electronic structure calculations

Conformation of 1,2-dimethoxyethane from ab initio electronic structure calculations

Conformations and Structures of Poly(oxyethylene) Melts from Molecular Dynamics Simulations and Small-Angle Neutron Scattering Experiments

Polyethyleneoxide‐Dynamics in Aqueous Solutions Studied by Nuclear Magnetic Relaxation

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