Solid‐state polymerization of linear and cyclic acetylenes

“…23,24 While the molecular packing of the active diacetylene monomer in EBT film is not the same as that of MD-55 film, 12 both contain the pentacosa-10,12-diynoate ion. Thus, the packing of pentacosa-10,12-diynoate ions is also dependent on the size and chemistry of the cation associated with the carboxylate end-group and this leads to dramatic differences in sensitivity.…”

Section: Ia Chemical Background and General Experiencementioning

confidence: 99%

Temperature and hydration effects on absorbance spectra and radiation sensitivity of a radiochromic medium

et al. 2008

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The effects of temperature on real time changes in optical density ͑⌬OD͒ of GAFCHROMIC ® EBT film were investigated. The spectral peak of maximum change in absorbance ͑ max ͒ was shown to downshift linearly when the temperature of the film was increased from 22 to 38°C. The ⌬OD values were also shown to decrease linearly with temperature, and this decrease could not be attributed to the shift in max . A compensation scheme using max and a temperature-dependent correction factor was investigated, but provided limited improvement. Part of the reason may be the fluctuations in hydration of the active component, which were found to affect both position of absorbance peaks and the sensitivity of the film. To test the effect of hydration, laminated and unlaminated films were desiccated. This shifted both the major and minor absorbance peaks in the opposite direction to the change observed with temperature. The desiccated film also exhibited reduced sensitivity to ionizing radiation. Rehydration of the desiccated films did not reverse the effects, but rather gave rise to another form of the polymer with absorbance maxima upshifted further 20 nm. Hence, the spectral characteristics and sensitivity of the film can be dependent on its history, potentially complicating both real-time and conventional radiation dosimetry.

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“…1 Large sidegroups attached to the diacetylene molecule reduce interchain interaction while -conjugation delocalizes the corresponding electron states. As criteria were developed for successful polymerization in monomer single crystals [2][3][4][5][6][7] two classes of PDAs emerged with a strong fundamental exciton centered either near 2.0 eV or 2.3 eV which are called blue and red chains by the color of partially polymerized crystals. Despite that di¤erence X-ray and Raman studies indicate the same basic building block, C C C=C .…”

Section: Introductionmentioning

confidence: 99%

Stark effect and Franz-Keldysh effect of a quantum wire realized by conjugated polymer chains of a diacetylene 3NPh2

et al. 2010

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Conjugated polymer chains diluted in monomer single crystals of a novel diacetylene, 1,10-bis(diphenylamino)-4,6-decadiyne, represent quantum wires of long range coherence. They di¤er from most polydiacetylenes by their repeat unit that consists of two C 4 units with twisted molecular planes. The resulting modi…cation of exciton and band states is studied by electroabsorption which resolves an increase of the exciton transition energy to 2.399 eV and of the free electron gap to 3.158 eV. The Stark shift of the exciton reveals a signi…cant reduction of the exciton radius by about 40 % to 6 1 Å which is consistent with a similar increase of the exciton binding energy to 759 meV. The lineshape of electroabsorption spectra at the free electron gap is for …elds larger than 30 kV/cm in accordance with the one-dimensional Franz-Keldysh e¤ect and yields a reduced mass of 0.07 m 0 larger than in other PDA. Spectra at smaller …elds are distorted by contributions of a weak dipole allowed and a forbidden exciton 38 and 12 meV, respectively below the bandgap.Coherent coupling of free electrons and vibrational modes leads to replicas of the Franz-Keldysh e¤ect. Since light polarized parallel to the conjugated chain excites two propagating modes in the monomer crystals the quantitative analysis was restricted to EA spectra taken with perpendicular polarization in samples which transmit only the weakly absorbed polariton mode.

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Solid‐state polymerization of linear and cyclic acetylenes

Cited by 116 publications

References 24 publications

A rational design of molecular materials

A rational design of molecular materials

Temperature and hydration effects on absorbance spectra and radiation sensitivity of a radiochromic medium

Stark effect and Franz-Keldysh effect of a quantum wire realized by conjugated polymer chains of a diacetylene 3NPh2

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