Insulated Polyacetylene Chains in an Inclusion Complex by Photopolymerization

Dinca, Steluta; Allis, Damian G.; Lashua, Amanda F.; Sponsler, Michael B.; Hudson, Bruce S.

doi:10.1557/opl.2015.486

Cited by 6 publications

(7 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The initial effect of the CW broadband irradiation on the DIBD/urea inclusion compounds is the appearance of two strongly resonantly enhanced bands at 1121 and 1509 cm –1 and a weak band at 1293 cm –1 (see the insets of Figure ). We observed similar polyene product features when the crystals were subjected to 254 or 532 nm radiation . The Raman spectra of the confined diiodopolyene chains are nearly identical to spectra of trans -(CH) n prepared by solution methods and with those previously reported for conjugated polymer trans -(CH) n . ,, The similarities between the two strongest modes in polymerized DIBD/urea inclusion compounds and trans -(CH) n seen around 1100 cm –1 (characteristic of a mixture of C–C single bond stretch modes and C–H in-plane bending modes) and around 1500 cm –1 (mainly due to CC bond stretches) ,, indicate that the formed diiodo-oligopolyene chains in our samples must also be in a fully extended zigzag form (all- trans ); Raman bands arising from the cis -isomer (configuration) of (CH) n are not observed .…”

Section: Resultssupporting

confidence: 79%

Preparation of Ordered Polyacetylene by Solid-State Polymerization in Nanoscale Confinement

et al. 2020

Self Cite

View full text Add to dashboard Cite

We report a novel, highly effective strategy for controlling the synthesis of polyacetylene as a guest in an organic host crystal by monitoring in situ an elimination−condensation polymerization reaction. Specifically, in this process, the polymer material is forced to have its chains extended and aligned such that translational periodicity applies, producing a bond alternation potential that has a symmetric double minimum. The synthetic approach used is photochemical elimination of iodine from a conjugated diene, (E,E)-1,4-diiodo-1,3-butadiene, which forms a commensurate and fully ordered urea inclusion compound. Photochemical cleavage of the terminal C−I bonds results in elimination of iodine from the single crystal and formation of C−C bonds between adjacent radicals to produce the conjugated 1,8-diiodo-1,3,5,7-octatetraene and subsequent longer polyene species. The combination of in situ crystal mass-loss measurements and vibrational Raman spectroscopy demonstrates clearly the presence of new polyene chains and loss of iodine from the urea substructure. The first few product oligopolyenes exhibit very strong Raman scattering with the most intense vibrational features decreasing in frequency for longer chains approaching an asymptotic limiting frequency that mimics the behavior of conjugated polyenes of known lengths from previous vibrational Raman studies. With extensive irradiation, the mass loss approaches that anticipated from the crystal stoichiometry and, at the same time of irradiation, the Raman intensity largely disappears. These results demonstrate that the reaction reported here proceeds to completion, leading to a quasi-one-dimensional array of isolated polyacetylene chains that are constrained to be in a continuous extended, all-trans conformation within the tunnels formed by the urea crystal lattice.

show abstract

Section: Resultssupporting

confidence: 79%

Preparation of Ordered Polyacetylene by Solid-State Polymerization in Nanoscale Confinement

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…The strong tetragonal urea feature at 1010 cm −1 is shifted to 1022 cm −1 , the value observed for hexagonal urea. Irradiation with ultraviolet (UV) light results in new Raman modes near 1509 and 1125 cm −1 [ 86 ] ( Figure 10 a), nearly identical to spectra of trans -(CH) x prepared in solution [ 87 ]. The 254 nm radiation used in this experiment has very limited penetration into the DIBD–urea complex due to the high optical density.…”

Section: In Situ Synthesis Of Oriented Insulated Polyacetylenementioning

confidence: 99%

“… Raman spectra with 532 nm excitation of ( a ) DIBD–UIC after irradiation at 254 nm; ( b ) trans –(CH) x ; ( c ) crystalline DIBD; and ( d ) tetragonal urea [ 86 ]. The ν n values at the top are the mode frequencies for polyacetylene fundamental transitions and their overtones.…”

Section: Figurementioning

confidence: 99%

Polyacetylene: Myth and Reality

Hudson

2018

Materials

View full text Add to dashboard Cite

Polyacetylene, the simplest and oldest of potentially conducting polymers, has never been made in a form that permits rigorous determination of its structure. Trans polyacetylene in its fully extended form will have a potential energy surface with two equivalent minima. It has been assumed that this results in bond length alternation. It is, rather, very likely that the zero-point energy is above the Peierls barrier. The experimental studies that purport to show bond alternation are reviewed and shown to be compromised by serious experimental inconsistencies or by the presence, for which there is considerable evidence, of finite chain polyenes. In this view, addition of dopants results in conductivity by facilitation of charge transport between finite polyenes. The double minimum potential that necessarily occurs for polyacetylene, if viewed as the result of elongation of finite chains, originates from admixture of the 11Ag ground electronic state with the 21Ag excited electronic singlet state. This excitation is diradical (two electron) in character. The polyacetylene limit is an equal admixture of these two 1Ag states making theory intractable for long chains. A method is outlined for preparation of high molecular weight polyacetylene with fully extended chains that are prevented from reacting with neighboring chains.

show abstract

“…The strong tetragonal urea feature at 1010 cm −1 is shifted to 1022 cm −1 , the value observed for hexagonal urea. Irradiation with ultraviolet (UV) light results in new Raman modes near 1509 and 1125 cm −1 [86] (Figure 10a), nearly identical to spectra of trans-(CH) x prepared in solution [87]. The 254 nm radiation used in this experiment has very limited penetration into the DIBD-urea complex due to the high optical density.…”

Section: In Situ Synthesis Of Oriented Insulated Polyacetylenementioning

confidence: 65%

“…The overall progress of the reaction can be monitored with loss of mass due to release of iodine. Raman spectra with 532 nm excitation of (a) DIBD-UIC after irradiation at 254 nm; (b) trans -(CH)x; (c) crystalline DIBD; and (d) tetragonal urea [86]. The νn values at the top are the mode frequencies for polyacetylene fundamental transitions and their overtones.…”

Section: In Situ Synthesis Of Oriented Insulated Polyacetylenementioning

confidence: 99%

Double minimum potential of polyacetylene: Consequences of ignoring

Hudson¹

2020

Preprint

View full text Add to dashboard Cite

Polyacetylene, the simplest and oldest of potentially conducting polymers, has never been made in a form that permits rigorous determination of its structure. Trans polyacetylene in its fully extended form will have a potential energy surface with two equivalent minima. It has been assumed that this results in bond length alternation. It is, rather, very likely that the zero-point energy is above the Peierls barrier. The experimental studies that purport to show bond alternation are reviewed and shown to be compromised by serious experimental inconsistencies or by the presence, for which there is considerable evidence, of finite chain polyenes. In this view, addition of dopants results in conductivity by facilitation of charge transport between finite polyenes. The double minimum potential that necessarily occurs for polyacetylene, if viewed as the result of elongation of finite chains, originates from admixture of the 1 1 A g ground electronic state with the 2 1 A g excited electronic singlet state. This excitation is diradical (two electron) in character. The polyacetylene limit is an equal admixture of these two 1 A g states making theory intractable for long chains. A method is outlined for preparation of high molecular weight polyacetylene with fully extended chains that are prevented from reacting with neighboring chains.

show abstract

Insulated Polyacetylene Chains in an Inclusion Complex by Photopolymerization

Cited by 6 publications

References 18 publications

Preparation of Ordered Polyacetylene by Solid-State Polymerization in Nanoscale Confinement

Preparation of Ordered Polyacetylene by Solid-State Polymerization in Nanoscale Confinement

Polyacetylene: Myth and Reality

Double minimum potential of polyacetylene: Consequences of ignoring

Contact Info

Product

Resources

About