Polysilanes physical properties

Physical properties of the polysilanes depend greatly upon the nature of the organic groups bound to silicon. A few of the many polysilanes are listed in Table I. Typically the linear polysilanes are thermoplastics, soluble in organic solvents like toluene, ethers,... 

We now wish to report the syntheses and physical properties of polysilanes substituted with a phenolic group and carboxylic groups, and polysiloxanes with a phenolic group directly bonded to Si(Figure 2). We also describe basic aqueous development of these materials. 

As explained in the introduction, the polysilanes (and related polygermanes and poly-stannanes) are different from all other high polymers, in that they exhibit sigma-electron delocalization. This phenomenon leads to special physical properties strong electronic absorption, conductivity, photoconductivity, photosensitivity, and so on, which are crucial for many of the technological applications of polysilanes. Other polymers, such as polyacetylene and polythiophene, display electron delocalization, but in these materials the delocalization involves pi-electrons. 

The organopolysilanes are those compounds containing at least one silicon-silicon bond and one silicon-carbon linkage. This review is mainly concerned with the chemistry of aliphatic derivatives of polysilanes. Consideration of aromatic organopolysilanes is excluded from this review except as far as they are used as intermediates for synthesis and their properties correlate with the aliphatic silicon-silicon compounds, because the aromatic organopolysilanes have recently been well reviewed elsewhere (31,51, 73, 76a, 212). Physical properties of the polysilanes also are excluded from consideration except for spectral properties of ultraviolet absorption and nuclear magnetic resonance, since they are well summarized in earlier excellent reviews and texts (8, 34, 35, 51,131,132). 

In this section, for convenience, we first deal with the synthesis and some physical properties of permethylated polysilanes, and then synthesis of other peralkylated and partially phenylated methyl polysilanes. Finally, chemical reactions of all such types of compounds will be discussed together. 

This section will demonstrate the first sergeants and soldiers-type helix command surface experiment, in which thermo-driven chiroptical transfer and amplification in optically inactive polysilane film from grafted (or spin-coated) optically active helical polysilane onto quartz substrate [92]. Although helix and optical activity amplification phenomena based on the sergeants and soldiers principle was mainly investigated in polymer stereochemistry, the orientation and physical properties of a thick layer deposited onto a solid surface and controlled by a monolayer command film based on command surface principles was established in photochemical material and surface science [93,94]. Both sergeants and soldiers and command surface experiments appear to have been developed independently. 

The photochemistry of organosilicon compounds has been extensively investigated not only from synthetic and mechanistic perspectives, but also with the intent of determining characteristic chemical and physical properties. Very recently, Steinmetz reviewed the area of organosilane photochemistry in which he focused on the reactivities of mono-, di-, tri-, and polysilanes. The most interesting and important point of that review is the differences in the reactivity that exist between organosilicon compounds and the corresponding all-carbon compounds. 

The synthesis of polysilanes and the subsequent study of their physical properties have led to promising results, thus stimulating researchers to expand the field. 

Many of the physical properties of polysilanes depend on the actual substituents present on silicon. However, polysilanes have some distinct features in comparison to other polymers which is a direct result of the unique characteristics that a catenated chain of silicon atoms provide. These can be summarized as follows ... 

Physical properties of polysilanes vary greatly depending upon the nature of the organic substituents attached to silicon. Poly(dimethylsilane) (1) and poly(diphenylsilane) (2) are a highly crystalline in-... 

Since their discovery in the early 80 s soluble polysilanes became the subject of numerous papers in differents fields synthesis, physical properties, optical properties and applications. Among them very few are devoted to the actual molecular wei t determination by... 

The last comprehensive review of polysilanes was given 20 years ago by Miller and Michl [3]. Since then, considerable work has been carried out to find a perfect method for their synthesis. Special interest has also been directed to the characterization of polysilanes to explain their special physical properties. 

The backbone of polysilanes exclusively consists of catenated Si atoms and their physical properties largely depend on the nature of the Si-Si bond and on the substituents present. 

Polysilanes have attracted considerable attention since 1989 because of their many interesting chemical and physical properties. Two recent reviews have summarized the previous theoretical studies of the electronic structure of polysilanes. Ortiz showed that KT is not a good approximation for describing the IPs of short linear polysilanes. On the other hand, using the Green s function... 

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