Higher-order structure and thermal transition behaviour of poly(di-–hexylsilane)

Kyotani, Hiroko; Shimomura, Masaki; Miyazaki, Miyuki; Ueno, Katsuhiko

doi:10.1016/0032-3861(95)93589-e

Cited by 16 publications

(11 citation statements)

References 18 publications

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“…The LT spectra show weak additional bands in the region of the HT maxima. The LT maxima are in line with reported data on the solid phases of poly(di- n -hexylsilylene) ( 1 ) , and are characteristic of emission from all-trans segments. It is conspicuous that in the LT phases emission maxima are identical, whereas the LT solid state UV spectra show distinct differences.…”

Section: Resultssupporting

confidence: 90%

Structural, Photophysical, and Conductive Properties of n-Hexyl Substituted Hybrid Polysilylene−Polysilyne Networks

Walree¹,

Cleij²,

Jenneskens³

et al. 1996

Macromolecules

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Structural, photophysical, and charge transport properties of n-hexyl substituted polysilylenes containing 5, 33 or 67% n-hexylsilyne branching points were investigated. According to WAXD, DSC, and vibrational studies, introduction of branching points partially reduces the high degree of crystallinity of linear poly(di-n-hexylsilylene). A thermal transition occurs in all polymers, which leads to solid state thermochromic behavior. Solution thermochromism is also observed. It is shown that in the partially branched polymers the narrow band gap of polysilynes is accompanied by an exciton delocalization approaching that of linear polysilylenes. In the solid state, charge carrier mobilities, determined with the pulse-radiolysis time-resolved microwave conductivity technique, are high but decrease with increasing branching. They range from 1.5 × 10-5 for the linear polymer to 7.6 × 10-7 m2 V-1 s-1 for the polymer with 67% branching sites. At the thermal transition an abrupt drop in the mobility is observed, of which the magnitude decreases with increasing branching. The branching points appear to act as scattering points for both exciton and charge carrier migration.

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Section: Resultssupporting

confidence: 90%

Structural, Photophysical, and Conductive Properties of n-Hexyl Substituted Hybrid Polysilylene−Polysilyne Networks

Walree¹,

Cleij²,

Jenneskens³

et al. 1996

Macromolecules

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“…9a-d). Similar patterns were observed previously by Kyotani et al [36]. By delicately varying experimental conditions near T c , when nucleation of the crystalline ordered phase within the hcm takes place, it appears possible to obtain separately, one at a time, narrow UV bands (half-width ≤1000 cm −1 ) with λ max either~375, or~365, or~355 nm (Fig.…”

Section: Uv Criteria Of Assignment Of Polysilane Modificationssupporting

confidence: 80%

Regularities and Peculiarities of Solid Polydialkylsilane Order-Disorder Transitions as Studied by Optical (UV, Raman and IR) Spectroscopy

Bukalov

Leites

West³

2010

Silicon

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As a result of systematic studies of numerous polydi-n-alkylsilane order-disorder transitions using a combination of UV, Raman, IR as well as XRD methods some generalizations are made concerning the nature of these processes. A criterion is proposed for a given UV band assignment to a given polymer modification based not only on its λ max value but also on the band width, contour and temperature behaviour of these parameters. Three types of ordering possible for these polymers were shown not to be necessarily interrelated. Side chain "melting" does not inevitably lead to thermochromism while thermochromic structural transitions can occur within the same phase.

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“…The interband σ-σ* transition of solid pdHexSi displays sensitivity to its processing and/or thermal history with, in at least one instance, the anomalous appearance of an additional 390 nm UV absorption peak. 31 Other studies have convincingly demonstrated the existence of Si backbone conformations other than the conventional trans-planar (or anti, A), gauche (G), and helical forms. Methyl/ethyl or all ethyl oligosilane modeling studies 28,29 have identified a large number of thermodynamically stable intermediate Si backbone conformations and these are referred to as transoid (T), deviant (D) and ortho (O) with approximate Si-Si-Si-Si dihedral angles of 170°, 150°and 90°respectively (with T+/T-and D+/D-for both positive and negative helicities).…”

Section: Introductionmentioning

confidence: 98%

“…With respect to the crystalline phase of solid pdHexSi, the nominal 372 nm absorption band often appears to contain a distinguishable shoulder near 360 nm. The interband σ−σ* transition of solid pdHexSi displays sensitivity to its processing and/or thermal history with, in at least one instance, the anomalous appearance of an additional 390 nm UV absorption peak …”

Section: Introductionmentioning

confidence: 99%

X-ray Diffraction and Molecular Modeling Studies of Poly(di-n-alkylsilanes): The Near Planar Type Phases of Poly(di-n-butylsilane) and Poly(di-n-hexylsilane)

Winokur

West

2003

Macromolecules

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X-ray diffraction and molecular modeling have been used to investigate the near planar solid-state phases of poly(di-n-hexylsilane) (pdHexSi) and poly(di-n-butylsilane) (pdBuSi). Structure refinement of diffraction data in conjunction with oligomer cluster energy calculations provides a more unified picture of both the main chain and side chain conformations. In both polymers the alkyl side chain construction is closely identified as an asymmetric cisoid-transoid conformational arrangement. Full refinement of the pdHexSi data identifies subtler features in the alkyl chain organization. All major trends and key structural features are paralleled in empirical MM3 based modeling of isolated di-nbutylsilane and di-n-butylsilane oligomers. Zero-temperature gas-phase calculations identify a well-defined topology of energetically accessible main chain and side chain conformations. Increasing the side chain length, from butyl to hexyl, changes both the distribution and make up of the low energy structures. A combination of intrachain and interchain packing energy constraints stabilize the planar form of poly-(di-n-hexylsilane). Intrachain interactions are significantly weaker in poly(di-n-butylsilane).

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Higher-order structure and thermal transition behaviour of poly(di-–hexylsilane)

Cited by 16 publications

References 18 publications

Structural, Photophysical, and Conductive Properties of n-Hexyl Substituted Hybrid Polysilylene−Polysilyne Networks

Structural, Photophysical, and Conductive Properties of n-Hexyl Substituted Hybrid Polysilylene−Polysilyne Networks

Regularities and Peculiarities of Solid Polydialkylsilane Order-Disorder Transitions as Studied by Optical (UV, Raman and IR) Spectroscopy

X-ray Diffraction and Molecular Modeling Studies of Poly(di-n-alkylsilanes): The Near Planar Type Phases of Poly(di-n-butylsilane) and Poly(di-n-hexylsilane)

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