Ab Initio Oligomer Approach to Vibrational Spectra of Polymers: Comparison of Helical and Planar Poly(p-phenylene)

Cuff, Lilee; Kertész, Miklós

doi:10.1021/ma00081a022

Cited by 69 publications

(55 citation statements)

References 7 publications

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“…The ratio of I B /I A rockets from benzene to P2P, then monotonous decreases with increasing the oligomer length. The trend of the ratio to the long-chain polymer is almost zero, this is consistent with the Raman spectra of PPP, 36,47 in which no double peaks were observed. Thus, I B /I A is also a pretty good indicator for estimating the length of the POP molecules.…”

Section: Modes Around 1600 CM −1supporting

confidence: 87%

“…[33][34][35] The ratio of the intensities of these two peaks is also an indicator of the inter-ring torsion angle. [36][37][38][39] In PPP materials, all the molecular orbitals can be divided into delocalized orbitals and localized orbitals. Theoretical calculations 37,44 further showed that the delocalized orbitals are mainly associated with the C atoms on the long molecular axis and strongly sensitive to the conjugation (chain length and planarity), whereas the localized orbitals are mainly contributed by the off-axis C atoms and are far less susceptible to conjugation effects.…”

Section: CM −1 Mode and 1280 Cm −1 Modementioning

confidence: 99%

“…The results are compared with previously published data. [33][34][35][36][37][38][39] A new method is introduced to estimate the chain length of POPs and PPP materials.…”

Section: Introductionmentioning

confidence: 99%

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Chain length effects of p-oligophenyls with comparison of benzene by Raman scattering

Zhang

Chen

2018

AIP Advances

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Raman scattering measurements are performed on benzene and a number of p-oligophenyls including biphenyl, p-terphenyl, p-quaterphenyl, p-quinquephenyl, and p-sexiphenyl at ambient conditions. The vibrational modes of the intra-and intermolecular terms in these materials are analyzed and compared. Chain length effects on the vibrational properties are examined for the C-H in-plane bending mode and the inter-ring C-C stretching mode at around 1200 cm −1 and 1280 cm −1 , respectively, and the C-C stretching modes at around 1600 cm −1 . The complex and fluctuating properties of these modes result in an imprecise estimation of the chain length of these molecules. Meanwhile, the obtained ratio of the intensities of the 1200 cm −1 mode and 1280 cm −1 mode is sensitive to the applied lasers. A librational motion mode with the lowest energy is found to have a monotonous change with the increase in the chain length. This mode is simply relevant to the c axis of the unit cell. Such an obvious trend makes it a better indicator for determining the chain length effects on the physical and chemical properties in these molecules.

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Section: Modes Around 1600 CM −1supporting

confidence: 87%

Section: CM −1 Mode and 1280 Cm −1 Modementioning

confidence: 99%

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Chain length effects of p-oligophenyls with comparison of benzene by Raman scattering

Zhang

Chen

2018

AIP Advances

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“…1. According to HF calculations 26,28 as well as x-ray reflection experiments 13,14,16 the difference between the bond lengths l 1 and l 2 within a ring is about 0.02 Å which is much smaller than the difference between either in-ring bond length l 1 or l 2 and the inter-ring bond length d. For computational convenience then, we have only considered a single bond length l within the ring, which largely reduces the computational effort. The geometry parameters l, d, h, and together with the torsional angle ␣ are optimized and listed in Table I, together with other reported theoretical and experimental results.…”

Section: A Conformationmentioning

confidence: 99%

“…Cuff and Kertesz 26 made an analysis of the intensity of the vibrational peaks in the Raman spectrum of oligomers based on ab initio Hartree-Fock ͑HF͒ calculations. Based on a comparison of their work with experimental results, they concluded that the most probable structure of PPP is nearly planar with an inter-ring torsional angle of less than 20°.…”

Section: Introductionmentioning

confidence: 99%

First-principles calculation of the conformation and electronic structure of polyparaphenylene

Miao

Camp

Doren

et al. 1998

The Journal of Chemical Physics

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A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers J. Chem. Phys. 120, 8608 (2004) In this article, an all-electron first-principles total energy calculation with Gaussian-type functions for the wave functions, for the exchange correlation potential, and for the charge density has been applied for single chains of polyparaphenylene ͑PPP͒. A local-density approximation within a helical band structure approach has been used. The calculated torsional potential shows a minimum at the torsion angle of 34.8°. The internal coordinates were optimized in the equilibrium conformation and are in good agreement with experimental and other theoretical results. The calculated direct band gap is 2.54 eV compared with the experimental result from UPS spectra of 3.4 eV for the gas phase. The band structure strongly depends on the conformation which suggests that the electronic properties can be modified in a wide range through doping or addition of side groups.

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Vibrational Spectroscopy of Conducting Polymers

Furukawa¹

2001

Handbook of Vibrational Spectroscopy

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The sections in this article are Introduction Infrared and R aman Spectra of Pristine Polymers R aman Spectra of Doped Polymers Doped Polyacetylene Doped Polythiophene Doped Poly( p ‐Phenylene) Doped Poly( p ‐Phenylenevinylene) Doping‐ and Photo‐Induced Infrared Absorption Infrared Spectra of Injected Carriers Concluding Remarks

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Ab Initio Oligomer Approach to Vibrational Spectra of Polymers: Comparison of Helical and Planar Poly(p-phenylene)

Cited by 69 publications

References 7 publications

Chain length effects of p-oligophenyls with comparison of benzene by Raman scattering

Chain length effects of p-oligophenyls with comparison of benzene by Raman scattering

First-principles calculation of the conformation and electronic structure of polyparaphenylene

Vibrational Spectroscopy of Conducting Polymers

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