Symmetrically substituted polysilylenes

Absorption spectra displaying a thermochromic transition have also been reported for several of the symmetrically substituted polysilylenes in the solid state. One example is that of PDHS, as reported by Kuzmany et al. (9) and shown in Figure 6. At 45 °C, a single absorption at 317 nm is observed, which is very similar to the absorption maximum for this polymer in solution... 

The configuration of the polysilylene chain can range from the simple structure of the symmetrically substituted homopolymer (in which R = R ), to the more complicated structure of the asymmetrically substituted homopolymer (in which R R ), and finally, to the very complex structure of the asymmetrically substituted copolymers, in which both stereochemical and comonomer sequences need to be considered. 

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... 

Symmetrical Dialkyl-Substituted Polysilylenes Because of their extremely sharp order-disorder transitions, the nonpolar, symmetrical dialkyl-substituted polysilylenes are almost ideal systems with which to test the predictions discussed earlier. The predicted solvent dependence of Tc was tested by performing a series of experiments with high-molecular-weight poly(di-n-hexylsilylene) in dilute solution. Experimental results for six solvents are listed in Table II, and the theoretically defined solvation coupling constants and solvent parameters are collected in Table III. 

---