Silicon backbone, aryl substitution

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... 

Soluble disubstituted polysilylenes are a class of polymers that recently has generated great interest. These polymers have the structure [-SiRR -] , in which R and R may be aryl or alkyl groups and R may be the same as R. The substituted polysilylenes exhibit a wide variety of physical properties, depending on the nature of R and R. Of particular interest is their intense UV absorption at 300-400 nm both in solution and in the solid state, a property conferred by the silicon backbone and accompanied... 

The TT-electron system-substituted organodisilanes such as aryl-, alkenyl-, and alkynyldisilanes are photoactive under ultraviolet irradiation, and their photochemical behavior has been extensively studied (1). However, much less interest has been shown in the photochemistry of polymers bearing TT-electron substituted disilanyl units (2-4). In this paper, we report the synthesis and photochemical behavior of polysiloxanes involving phenyl(trimethylsilyl)-siloxy units and silicon polymers in which the alternate arrangement of a disilanylene unit and a phenylene group is found regularly in the polymer backbone. We also describe lithographic applications of a double-layer system of the latter polymers. 

Polysilanes (or polysilylenes) consist of a silicon-catenated backbone with two substituents on each silicon atom (Structure 1). The groups R and R attached to the silicon chain can be of a large variety. Polysilanes with alkyl and/or aryl substituents have been the most thoroughly investigated [1-3], whereas polysilanes having at least a heteroatom substitution such as H, Cl, OR, NR2 have received much less attention [4]. The number of silicon atoms is usually from several hundreds to several thousands. 

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