Poly di-n-alkylsilanes

This result is further supported by the very short 130 + 10 ps lifetime combined with the remarkably high quantum yield of 0.43, both observed upon excitation at 335 nm, near the long-wavelength edge of the absorption band. These values combine to a radiative lifetime of 300 ps, which corresponds (33a) to an oscillator strength of 1.8. Similarly short emission lifetimes have been observed for other poly(di-n-alkylsilanes) di-n-pentyl, 200 ps, di-n-decyl, 150 ps. The average oscillator... 

Poly(arylether ketone), conducting, 7 524 Poly(aryl ether ketone)s, sulfonation reaction of, 23 717-718 Poly(di-n-alkylsilanes), thermochromic materials, 6 619... 

An investigation of poly(di- -alkylsilane)s with short side chains assumes a critical importance for a generalized understanding of the structures, energetics and phase transition of this novel class of polymers. The structures of the poly(di-n-alkylsilane) family are far more complicated than presumed to date, requiring a re-examination of our current understanding of the structure-property relationships of these important polymers. 

Above all, from the high resolution Si and NMR spectra and the relaxation times (Ti) of the poly(di-n-alkylsilane)s with shorter side chains in the solid state, this paper concludes that the conformation of PDMS takes... 

Rabddt JF, Hofer D, Miller RD, Fickes GN (1986) Studies of chain conformational kinetics in poly(di-n-alkylsilanes) by spectroscopic methods. Macromolecules, /9 611... 

Structure of which is identical to their corresponding low molecular weight disk-like counterparts. Rigid chain polymers, such as nucleic acids and polypeptides [5b, 66], are also well known to produce lyotropic columnar mesophases with appropriate solvents. The poly(di-n-alkylsilanes) and poly(di-n-alkylsiloxanes). Fig. 12, with only alkyl side groups and deprived of any mesogen [67] are examples of polymers showing thermotropic columnar mesophases which need to be analyzed in more detail. 

Fig. 12. Chemical structure of poly(di-n-alkylsilanes) and poly(di-n-alkylsiloxanes)...

Fig. 13. Square of the intercolumnar distance as a function of the number, p, of methylene groups in the alkyl side chains for the columnar mesophase of poly(di-n-alkylsilanes) at 100 °C...

From the above results, it is clear that the presence of classical mesogens is not necessary for linear chains like poly(di-n-alkylsilane)s or poly(di-n-alkoxyphos-phazene)s [77] to show a mesomorphic behaviour. This concept has also been applied to the case of poly(di-n-alkylsiloxane)s. For aUcyl chains containing between 2 and 6 carbon atoms, the materials were shown to form a columnar mesophase, in which the molecules are positionally and orienta-tionally ordered in a two-dimensional hexagonal lattice, but along the chain no long range correlations exists [78]. The most famous member of this series of polysiloxanes is polydiethylsiloxane which exhibits at room temperature a... 

In addition to the H-NMR experiments, p FT measurements have been carried out. Both isobaric and isothermal experiments were performed for all polymers. Figures 3 and 4 (left) show the isobaric measurements on the poly(di-n-alkylsilane)s, measured with a heating rate of 1 K/min. In the case of PD6S only one first-order phase transition from the all-trans crystalline to the... 

Winokur, M. J. West, R., X-ray Diffraction and Molecular Modeling Studies of Poly(di-n-alkylsilanes) The Near Planar Type Phases of Poly(di-n-butylsilane) and Poly(di-n-hexylsilane). Macromolecules 2003, 36(19), 7338-7347. 

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