Search results for "Polysilane"
showing 5 items of 5 documents
Synthesis and Characterization of SiC/MC/C Ceramics (M = Ti, Zr, Hf) Starting from Totally Non-oxidic Precursors
2002
The reaction of poly(dimethylsilane) (PDMS) and poly(dimethylcarbosilane) (PCS) with bis(cyclopentadienyl)M dichloride Cp2MCl2 (M ) Ti, Zr, Hf) complexes has been used as a new route to obtain ceramic materials based on SiC-containing M. The reaction is completed at a relatively low temperature, 900 °C, yielding the corresponding amorphous SiC/MC ceramics which have been characterized by means of 29 Si MAS NMR. These amorphous materials have been treated at higher temperatures, 1350 °C, under a purified argon atmosphere, yielding partially crystallized products which have been studied by X-ray powder diffraction and 29 Si MAS NMR. The effect of the composition of the mixture of precursors is
VEH electronic band structure of poly(phenylsilane)
1993
Abstract The electronic structure of all-trans syndiotactic and isotactic poly(phenylsilane) has been calculated using the valence effective Hamiltonian (VEH) method. The effects of attachment of the phenyl group on the electronic properties of polysilane are analysed in detail. The VEH results show a decrease of ionization potential and an increase of electron affinity which determine an important reduction of the bandgap. These features are correlated with σ−π and σ ∗ −π ∗ interactions between the silicon backbone and the phenyl group.
Multihydroxy-Functional Polysilanes via an Acetal Protecting Group Strategy
2010
A new acetal-protected monomer for Wurtz-type coupling to polysilanes, dichloro(3-(2,2-dimethyl-1,3-dioxolane-4-yloxy)propyl)methylsilane, referred to as dichloro(isopropylidene glyceryl propyl ether)methylsilane (DCIMS), has been introduced to synthesize a series of protected linear polysilane copolymers, poly[di-n-hexylsilane-co-(isopropylidene glyceryl propyl ether)methylsilane] (P(DHS-co-IMS)) via alkali-mediated reductive Wurtz-type coupling. The acetal protecting group proved stable under the harsh polymerization conditions. Differential scanning calorimetry combined with 1H, 13C, and 29Si NMR measurements confirmed composition and random structure of the obtained copolymers. After se…
Nonlinear optical susceptibilities of polysilanes: exciton effect
1992
Abstract Third-order nonlinear optical susceptibilities of σ-conjugated one-dimensional polymers have been calculated in a tight-binding model by taking account of the formation of excitons due to long-range Coulomb interactions. The spectrum of third-harmonic generation (THG) exhibits peaks due to excitons as well as unbound electron—hole states, in contrast to the linear absorption spectrum which is dominated by the lowest exciton state. The results are in excellent agreement with recent experiments in polysilanes not only for THG but also for linear absorption, two-photon absorption, and electroabsorption in a mutually consistent way.
Electronic structure of polysilanes: influence of substitution and conformation
1993
Abstract The valence effective Hamiltonian (VEH) quantum-chemical approach is used to investigate the electronic properties of polysilane. The valence band structure calculated for this fully saturated polymer is analyzed in terms of orbital contributions and compared to that of the closely related carbon polymer, polyethylene. The effects of alkyl substitution and silicon backbone conformation are studied by elucidating the modifications that these structural changes induce on the electronic valence band structure of all-trans unsubstituted polysilane. The VEH results predict a decrease of the band gap upon alkyl substitution and on going from helical to all-trans conformations.