Polysilanes Poly

The oxygen atom not only imparts polarity, but also flexibility, as was discussed156 for two early ether-substituted polysilanes, poly(5-oxaoctyl- -propylsilylene) and poly(5-oxaoctyl- -hexylsilylene). To investigate this further, Yuan and West, using the same standard Wurtz procedure, prepared a series of poly(oxaoctylmethylsilylene) isomers and their symmetrical counterparts, in which the position of the oxygen atom was varied in side-chain positions 5, 6, and 7.157... 

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. 

The Lewis basicity of the solvents was found to be more important for the solvatochromism than the solvent polarity, since such Si... solvent and Si... F interactions are competitive in the presence of solvents with donor atoms. In contrast, the analogous non-fluorinated polysilane, poly(methyl-/z-propylsilylene), revealed a disordered conformation in both coordinating and non-coordinating solvents. Additionally, the UV spectra of various molecular weight fractions of 87 showed an unusual molecular weight dependency an isosbestic point is apparent, suggesting an equilibrium between globule- and rod-like conformations at room temperature, which was also evident from the... 

Due to its relevance o single-layer photoreceptors, photogeneration in polymers is of considerable importance to xerography. The most widely studied are the polysilanes, poly(N-vinylcarbazole), and various doped polymers. 

In this chapter, we report measurements on a diaryl-substituted polysilane, poly[bis(p-n-butyl)phenylsilane] (PBPNBPS), in which the bulky phenyl groups may provide more substantial steric hindrance to rotational freedom than do the dialkyl substituents. Reported values of the wavelength of maximum electronic absorption are large (395 10 nm) and cannot be attributed solely to electronic substituent effects (4). 

Figure 11.7. Absorption and luminescence spectra of polysilanes (a) typical spectra in which Ea and Ep are the peaks of absorption and emission respectively, and 5E and AE are respectively the Stokes shift and the width at half height of the absorption band (b), (c) and (d) depict the spectra of a single screw-sense rod-like polysilane, poly(di- -butylsilane), and PMPS, respectively (Reprinted from ref. l Copyright 2000 Kluwer Academic Publishers).

Unlike polysilanes, poly(ferrocenylsilane)s do not have electron delocalization in their backbone. The electronic absorption of these polymers is typical of those known for unstrained ferrocene derivatives. The monomer ferrocenophanes, on the other hand, show bathochromic absorption (470-480 nm) in comparison to bis-trimethylsilylferrocene (448 nm) [44-46]. 

On the basis of theoretical calculations, the highdimensional silicon framework results in a smaller bandgap than that of the low-dimensional one [19,20]. In order to reduce the bandgap of the polysilanes, tiie synthesis of branched polysilanes, poly(organosilynes), has been attempted. 

When neat 18a is heated in an evacuated sealed tube at 130°C for 1 hour 19a is obtained quantitatively. The polymer 19a is soluble in THF and the sample purified from THF-hexane is a yellow fibrous material with A/vv = 5.2 X 10 and A/n = 3.4 x 10, and readily forms amber, free-standing films by casting from toluene solution. By this ROP method, symmetrically and unsymmetrically substituted poly(ferrocenylsi-poly(ferrocenylsilanes) (19) [71,72] and polysilane-poly(ferrocenylsilane) copolymers, (20) [73] have been prepared. The ROP of [l]ferrocenophane with unsymmetrically methylated cyclopentadienyl rings (21) to investigate the C—Si bond cleavage mechanism in the thermal ROP gives a polymer (22) in which three types of silicon environment exist, showing that... 

Rulkens, R., Resendes, R., Verma, A. et al. (1997) Ring-opening copolymerization of cyclotetrasilanes and sificon-bridged [ 1 ]fenocenophanes Synthesis and properties of polysilane-poly(ferrocenylsilane) random copolymers. 

---