Polysilane simple

Most recently, a simple, mild, one-pot immobilization method was developed to attach the rigid rod-like helical polysilane, poly( -decyl-/-butylsilylene), via a siloxy linkage to hydrophilic quartz or mica substrate surfaces.28 195 Triethylamine was used as a catalyst to couple the Si-H and/or Si-OR termini of the dialkylpolysilane chains (which are generated during the course of Wurtz-type synthesis and workup)51,195 with the surface -OH groups. AFM, UV, and IR data were used to analyze the reactions. 

Examination of the absorption spectra of the new polysilane materials reveals a number of interesting features (14). As shown in Table III, simple alkyl substituted polymers show absorption maxima around 300-310 nm. Aryl substitution directly on the silicon backbone, however, results in a strong bathochromic shift to 335-345 nm. It is noteworthy that 4, which has a pendant aromatic side group that is buffered from the backbone by a saturated spacer atom, absorbs in the same region as the peralkyl derivatives. This red shift for the silane polymers with aromatic substituents directly bonded to the backbone is reminiscent of a similar observation for phenyl substituted and terminate silicon catenates relative to the corresponding permethyl derivatives... 

An even simpler duplication process based on the same principle is shown in Figure 5.29(B). If a hole-injecting electrode is used instead of a photosensitive layer, simple electrostatic charging allows the pattern to be read and transferred.148 Other new technologies based on the photopatteming of polysilanes are being developed, and may become commercialized in the future. 

Cross-metathesis applications, 11, 200 enynes, 11, 282 in ethenolysis, 11, 198 Lewis-basic substrates, 11, 193 in one-pot reactions, 11, 197 for reagent synthesis, 11, 188 as simple metathesis reaction, 1, 171 Crotyltributyltins, with aldehydes, 9, 352 Crown ether clathrates, diorganozinc compounds, 2, 335 Crown ether-pendant polysilanes, preparation, 3, 577 Crown-ethers, as hosts, 12, 813... 

Doping with iodine, on the other hand, gave lower conductivities (ca 10-6 to 10-8 Scm-1, see Table 1), but which could be correlated with the ionization potentials of the polymers (lower ionization potentials giving higher conductivity). This is consistent with simple electron transfer from the polysilane to the iodine, with formation of delocalized holes along the polysilane chain. 

Simple admixture of arylamines to polysilanes also serves to increase the conductivity upon iodine doping. Addition of 30 wt% of AWW. iV -tetrakisO-methylphenyl)-1,3-diaminobenzene to (PhSiMe)n increased the conductivity of this polymer to 3 x 10"4 Scm-1. 

The formation of silicon-silicon bonds constitutes the key step in these syntheses. To avoid the use of sodium, a simple, inexpensive, and practical electrochemical technique using an undivided cell, a sacrificial anode, and a constant current density has been developed allowing a facile synthesis of di-, tri-, or polysilanes including polydimethylsilane. 

Interest in polysilanes was reawakened in 1975, when Yajima and Hayashi found that permethylpolysilane could be transformed into silicon carbide by heating at high temperatures. Soon afterward, papers on soluble, meltable polysilanes began to appear. The literature on polysilanes has grown rapidly since that time. The early focus on the synthesis and simple characterization of polysilanes has given way to detailed physical studies of the structure of these polymers, and of their electronic and photophysical properties. 

The preparation, manufacture, and reactions of SiC have been discussed in detail in Gmelin, as have the electrical, mechanical, and other properties of both crystalline and amorphous of SiC. Silicon carbide results from the pyrolysis of a wide range of materials containing both silicon and carbon but it is manufactured on a large scale by the reduction of quartz in the presence of an excess of carbon (in the form of anthracite or coke), (Scheme 60), and more recently by the pyrolysis of polysilanes or polycarbosUanes (for a review, see Reference 291). Although it has a simple empirical formula, silicon carbide exists in at least 70 different crystalline forms based on either the hexagonal wurtzite (ZnS) structme a-SiC, or the cubic diamond (zinc blende) structme /3-SiC. The structmes differ in the way that the layers of atoms are stacked, with Si being fom-coordinate in all cases. 

Alkylated and arylated oligosilanes and polysilanes, the silicon analogues of alkanes and of polyethylene, have recently attracted considerable attention (Miller and Michl, 1989). Unlike saturated hydrocarbons, these materials absorb in the near UV region. The reasons for this are related to the electropositive nature of silicon and can be understood in simple terms (Michl,... 

Copolymerization of two different dichlorosilanes can also be achieved by the reduction using a sacrificial anode [177,178]. It is interesting that copolymerization of sila-functional dichlorosilanes with simple dichlorosilanes took place smoothly to provide an elegant route to functionalized polysilanes [178]. As to the synthesis of sila-functional polysilanes, the electrochemical reduction of perfluoroalkyl-substituted trichlorosilane to give perfluoroalkyl-substituted polysilane is interesting [179]. 

The usual procedure in preparations of polysilanes and polygermanes is to circulate the simple hydride through an ozonizer-type discharge until practically all of it has decomposed and the gas being circulated is principally hydrogen. The product hydrides are trapped out in a suitable cold trap in the gas circuit. If the desired product vapors were allowed to circulate continually through the discharge, the product would... 

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