SYNTHESIS AND CHARACTERISTIC OF POLYSILANES CONTAINING Si-H BOND

Three kinds of polysilanes containing Si-H bond, ■CH_3SiCH_3■_x■CH_3SiH■_y■_n and■PhSiPh■_π■CH_3SiH■_y■CH_3SiCH_3■, have been synthesized. The structures of these copolymers were investigated by IR, ~1H-NMR and ^(13)C-NMR and their molecular weights were measured.

无扰Polysilane链的热力学函数

采用旋转异构态模型和二级相互作用近似，计算了无扰Ｐｏｌｙｓｉｌａｎｅ链的内能、自由能和熵。

STUDY ON THE SOLUTION FLUORESCENCE QUENCHING FOR POLYSILANES

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CALCULATION OF CONFORMATIONAL ENTROPY AND FREE ENERGY OF POLYSILANE CHAIN

The conformational entropy S and free energy F were calculated by exact enumeration of polysilane chain up to 23 segments with excluded volume (EV) and long-range van der Waals (VW) interaction. A nonlinear relation between SEV+VW and chain length n was found though S-EV was found to vary linearly with n. We found that the second-order transition temperature of polysilane chain with VW interaction increases with the increase of chain length, while that of polysilane chain without VW interaction is chain length independent. Moreover, the free energies FEV+VW and F-EV are both linearly related with n, and FEV+VW < F-EV for all temperatures.

Synthesis and Characterization of Fully-Functionalized Polysilanes for Photorefractive Materials

Hydrogen-containing polysilanes and chromophore-containing polysilanes are prepared by traditional Wurtz coupling and subsequent hydrosilylation. They are characterized by (HNMR)-H-1, FT-IR, UV/VIS spectroscopies, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC).

STUDIES ON THE POLYSILANE CONSISTING CYCLODISILAZANE UNITS IN THE MAIN CHAIN

Since the reactivity of Me_2SiCl_2(Ⅰ) and ■(Ⅱ) are very different. it is difficult to cocondensate the above two monomers with sodium in general Wurtz reaction. We have proposed a modified method to prepare copolymer containing permethylpolysilane segments and cyclodisilazane units by reaction of (Ⅱ)with Na at first, then adding (Ⅰ) into the mixture to proceed with further reaction.The obtained copolysilanes are pale yellow elastic substance and soluble in common solvents. The amounts of N in the copolymers are influenced by the operating conditions of the synthetic method. The resultant products were characterized by IR, UV, NMR, and elementary analysis. The highest molecular weight determined by gel permeation chromatography is 60000.

Effects of PBr₃Addition to Polysilane Thin Films on Structures and Photovoltaic Properties

Organic thin film solar cells are potential next generation solar cells. Many p-type semiconductors have been used in organic solar cells, but there have been far fewer reports involving n-type organic semiconductors. Developing new n-type organic semiconductors is therefore desirable. Polysilane thin films were spin-coated from solutions containing phosphorus (P), and the effects of P addition on film microstructures and electronic properties as n-type semiconductors were investigated. Microstructures of poly-methyl-phenyl-silane (PMPS), dimethyl-polysilane (DMPS) and deca-phenyl-penta-silane (DPPS) thin films were investigated by X-ray diffraction and transmission electron microscopy. PMPS thin films doped with P (PMPS(P)) were amorphous upon annealing at 300&#176C, while DMPS(P) and DPPS(P) thin films exhibited crystalline structures. PMPS(P) and DMPS(P) thin films exhibited decreased electrical resistances upon P doping. The energy gaps of PMPS(P), DMPS(P) and DPPS(P) were 3.5, 3.9 and 3.8 eV, respectively. Decreased photoluminescence intensities of PMPS, DMPS and DPPS were observed upon P doping. The desorption of phenyl and methyl groups from PMPS(P) thin films was observed from Raman scattering measurements. Solar cells containing polysilane(P)/poly[3-hexylthiophene] heterojunction structures were fabricated and exhibited photovoltaic behavior.

Fabrication of Perovskite-Type Photovoltaic Devices with Polysilane Hole Transport Layers

Perovskite-type photovoltaic devices with polysilane hole transport layers were fabricated by a spin-coating method. In the present work, poly(methyl phenylsilane) (PMPS) and decaphenylcyclopentasilane (DPPS) were used as the hole transport layers. First, structural and optical properties of the PMPS and DPPS films were investigated, and the as-prepared PMPS and DPPS films were amorphous. Optical absorption spectra of the amorphous PMPS and DPPS showed some marked features due to the nature of polysilanes. Then, microstructures, optical and photovoltaic properties of the perovskite-type photovoltaic devices with polysilane hole transport layers were investigated. Current density-voltage characteristics and incident photon to current conversion efficiency of the photovoltaic devices with the polysilane layers showed different photovoltaic performance each other, attributed to molecular structures of the polysilanes and Si content in the present hole transport layers.

Microstructures and Photovoltaic Properties of Polysilane/C₆₀-Based Solar Cells

Polysilane/C60-based solar cells were fabricated and investigated. Two-types of devices with bulk heterojunction and heterojunction structures were examined and characterized. Addition of silicon-based polymer to the organic solar cells improved the conversion efficiency by wide optical absorption and high carrier mobility. Microstructures of the solar cells were investigated by using X-ray diffraction and transmission electron microscopy. Energy levels in the present solar cells were discussed.

Synthesis of Polysilanes Using Mg and Lewis Acid and the Consideration of This Reaction Mechanism

Reduction of dichlorosilanes with Mg metal in the presence of LiCl and Lewis acid such as FeCl2 or ZnCl2 was found to be the highly practical method for the synthesis of polysilanes (PS). This method is so useful and practical that PS can be prepared by stirring dichlorosilanes at room temperature. This method was successfully applied for the synthesis of various types of PS having a linear structure, a cyclic structure and silane-styrene copolymers as another type of PS. The structure of the reaction intermediates was also analyzed. At the initiation stage the results of FD-MS (Field desorption mass spectrometry) and GPC (Gel permeation chromatography) showed that linear oligomers were mainly formed by stepwise reactions, and then the high polymers and cyclic oligomers were formed in parallel.

Effects of Polysilane-Coating on Interface of Electrofusion Joints for Maintaining Strength

The fusion strength of electrofusion joints using the polyethylene (PE) pipe connection greatly depends on the amount of sand which adheres to the interface by wind and so on, because there is no flow of melted resin at the fusion interface on electrofusion joints. Therefore, it is necessary to develop a method to prevent the fusion strength from reducing even in the case of sand adhesion. In this study, the fusion interface coated with polysilane, a kind of silicon polymer, effectively prevented the reduction of the fusion strength even if contaminated by sand. It was found that it brought the improvement of the fusion strength since when there was polysilane on the fusion interface. PS deeply permeated the polyethylene layer and lowered the viscosity of polyethylene.

Helix Induction to Polysilane Chain Upon Wrapping by Sugar Derivatives and Related Chemistry

1 Results Helix induction to polymer chains is an active area of research these days. In most cases,optically-active units are attached to the polymers to induce helical conformation. Scheme 1Since the properties of σ-conjugated polymers like polysilanes are dependent on the conformation of the chain,it is particularly interesting to induce helix to oligo-and polysilanes. We have been working on the helix induction by host-guest complexation with sugar derivatives such as cyclodextrine and amylose.The l...

Study on Syntheses and Characterizations of Polymethylphenethylsilane, Polymethylcyclohexylsilane and their Copolymers

The effects of adding cosolvents of diglyme and 15 crown 5 to the reaction mixture of Wurtz type coupling of dichlorosilanes on the yield and relative molecular mass dispersity of polymethylphenethylsilane(PMPES) were discussed. The results show that addition of 10% (volume ratio of diglyme to toluene) diglyme as a cosolvent to the reaction mixture leads to the yield increase of PMPES with a monomodal distribution of relative molecular masses. Adding 10% diglyme to the reaction mixtures, the yields of polymethylcyclohexylsilane(PMCS) and copolymers (polymethylphenethylsilane co methylcyclohexylsilane), (the molar ratios of methylphenethyldichlorosilane to methylcyclohexyldichlorosilane were 2.0, 1.0 and 0.5, and the copolymers were abbreviated by Copolymers Ⅰ, Ⅱ, Ⅲ, respectively) are 47%, 52%, 54%, 53%, respectively. Their relative molecular masses ( w ) almost reach 10 5. These polysilanes were characterized by 1H NMR, IR and UV absorption spectrum.

SYNTHESIS AND OPTICAL-ELECTRONIC PROPERTIES OF POLY[METHYLTETRAPHENYLPHENYLSILYLENE-CO-BIS(METHYLPHENYLSILYL)ACETYLENE]

Poly(methyltetraphenylphenylsilylene-co-bis(methylphenylsilyl)acetylene) (PSA) was synthesized by the cocondensation reaction of methyltetraphenylphenyldichlorosilane and bis(chloromethylphenylsilyl)acetylene with sodium in toluene. The PSA thus obtained was soluble in most organic solvents, and its molecular weight was smaller than that of poly[(disilanylene)acetylenes] with alkyl- or aryl-substitution because of the great steric congestion of tetraphenylphenyl groups. The optical and electronic properties of the polymer were investigated. The results show that PSA has strong UV absorption and fluorescence emission, the maximum UV absorption wavelength of PSA is 330 nm, which shows a considerable red-shift in comparison with that of poly(methylphenylsilylene-co-methylphenylsilylacetylene) (PSI) and alkyl- substituted poly[(disilanylene)acetylenes]. A strong photoluminescence band at 470 nm in THF and 432 nm in benzene can be observed in the visible region, respectively. Treatment of the films of PSA with I 2 vapor afforded conducting films. The conductivity of PSA thin film doped with I 2 was measured to be 0.35 S cm -1 in the air which is lower than that of poly(methyltetraphenylphenylsilylene-co-bis(methylphenylsilyl)phenylene), but higher than that of σ-π polymers without tetraphenylphenyl groups. As an explanation, the tetraphenylphenyl group is a large π-electron-conjugated group; after being introduced to the Si atoms of the polysilanes, the interaction between π-electrons of the tetraphenylphenyl groups and the σ- electrons conjugated along the Si—Si bonds is increased strongly, and the σ-electrons can be conjugated more extensively along the main chain of the polysilanes.

Fabrication and Characterization of Poly[Decaphenylcyclopentasilane]-Based Solar Cells

Poly[decaphenylcyclopentasilane] (PDPS)-based photovoltaic cells were fabricated by using mixture solution of PDPS including boron and phosphorous elements. A doping effect of phosphorus and boron into PDPS was investigated on the performance of the photovoltaic devices. The solar cell provided short-circuit current density of 0.11 mA/cm2 and open-circuit voltage of 0.81 V under simulated sunlight. Microstructural analysis indicated that PDPS had an amor-phous structure, which would result in the photovoltaic properties.

THEORETICAL STUDIES ON THE STRUCTURES AND REACTIVITY OF SILYLENOIDS (Ⅰ)——STRUCTURES AND ISOMERIZATION OF SILYLENOID H_2SiLiCl

The structures of silylenoid H2SiLiCl have been studied by RHF/3-21G gradient method. Three equilibrium states and two isomerization transition states are located. The electronic energy, Mulliken populations, dipole moments and frontier molecular orbitals （FMO） of every structure and the isomeric barriers are also given and analyzed. Further single point calculations on the 3-21G optimum geometries were performed using 6-21G basis set. The calculations show that three-membered ring structure of H2SiLiCl is the most stable and detectable, and the "classical" tetrahedral form is not the local minimum on the potential energy surface.

SYNTHESIS AND STRUCTURE OF μ-O-BIS-[(PERMETHYL POLYSILANDIYL) DICYCLO-PENTADIENYL CHLOROZIRCONIUM]

α,ω-dichloropermethyl polysilane reacted sequentially with cyclopentadienyl sodium, n-butyl lithium and zirconium tetrachloride to produce sila-bridged dicyclopentadienyl zirconium dichlorides, (Me2Si)n(C5H4)2ZrCl2, which were hydrolyzed under basic conditions to yield the title compounds, [(Me2Si)n(C5H4)2ZrCl]2O. Their structures were characterized by elemental analyses, 1HNMR and MS. Furthermore the crystal structures of two complexes were determined by X-ray diffraction method. The crystal (n = 2) is monoclinic, space group P21/c with a= 14.268(4), b = 7.812(1), c = 31.050(5)A; β = 99.59°; Z = 4; the factor R = 0.039. The crystal (n=3) is monoclinic, space group C2 with a = 19.944(1), b = 17.117(1), c = 15.966 (1)A; β= 128.68°; Z= 4; the factor R= 0.033. The effect of sila-bridge on the structure and properties of these complexes are discussed.