Polysilylenes spectrum

Relationship to Electronic Properties. As a result of the close connection between bond conformation and electronic properties (4), the analysis of chain conformation in the polysilylenes has been of interest to researchers in this field, both from the experimental and theoretical viewpoints. As reported by Trefonas et al. (5), most asymmetrically substituted alkyl polysilylenes in solution at room temperature display an electronic absorption with ranging from 303 to 309 nm. The variable-temperature absorption spectrum of PMHS is shown in Figure 4 (4). At room temperature, max is 308 nm, and as the solution is cooled, there is a continuous red shift with the X x reaching 328 nm at -95 °C. Some workers 4, 6) suggest that this observation is a reflection of an increasing population of trans rotational states in the silicon backbone as the temperature is lowered. This suggestion is supported by the finding that these spectra can be adequately modeled by a rotational isomeric-state treatment (4). 

Other Polysilylenes. The symmetrically substituted poly(di-n-tetra-decylsilylene) is reported to have a TGTG trans-gauche-trans-gauche ) conformation, and a bathochromic shift is observed in the UV spectrum at 54 °G with Xjnax shifting from 322 to 350 nm (35). The structures of many polysilylenes may be more complicated than what have been discussed thus far. As an example, the DSG data for PMHS are shown in Figure 24, The figure shows that Tg (glass transition temperature) is 220 K and that two... 

We have previously suggested (9a, 1 0) a rotational isomeric state model to explain the solution thermochromism exhibited by the un-branched alkyl substituted polysilylenes. This model treats the absorption spectrum as a superposition of the spectra of Isolated... 

We have examined the emission spectra of a variety of polysilylenes as thin films and solutions. The solution fluorescence ther-mochromism provides evidence to support the rotational isomeric state model used to interpret the absorption spectrum. The structured character and low yield of phosphorescence in the alkyl polysilylenes suggest that the triplet is the immediate precursor to photochemical scission. The change in character of both fluorescence and phosphorescence on progressing from phenyl to naphthyl in the aryl series indicates that the transitions in the naphthyl polymers are principally ir—it. ... 

This chlorinated polysilylene after reaction with sodium in toluene at 110°C remained unchanged in molecular weight. The SEC trace of the sodium treated chlorinated polymer coincided with that of the original chlorinated polymer. The Si NMR spectrum of the solution before it was deactivated was also unchanged. 

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