- Helix magic. Thermo-driven chiroptical switching and screw-sense inversion of flexible rod helical polysilylenes
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An ideal optically active helical chromophoric polymer comprising a flexible rodlike silicon main chain and enantiopure alkyl side chains, poly{(S)-3,7-dimethyloctyl-3-methylbutylsilylene}, underwent a thermo- driven helix-helix transition at -20 °C in isooctane. The transition characteristics, including transition temperature, transition width, the population of right- and left-handed helical motifs, global shape, and screw- pitch, were to be characterized quantitatively by spectroscopically analyzing circular dichroism (CD) and UV absorption characteristics. This is based on the unique property of the rodlike polymer in which the CD band completely matches the corresponding UV band profile at all temperatures. Moreover, fine controlling the contents and chirality of an additional chiral silylene unit incorporated in the copolymers allows free manipulation of the transition temperature in the range from -64 to +79 °C. Molecular mechanics calculation showed remarkable differences in the potential energy curve of the main chain torsion angle between flexible and rigid rodlike polysilylenes. These results and knowledge gained should assist in designing and controlling new types of helix-helix transition polymers directed to diverse screw-sense related properties and applications.
- Fujiki, Michiya
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- Processes for manufacturing organochlorosilanes and dipodal silanes and silanes made thereby
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Processes are provided for producing organchlorosilanes and dipodal silanes in which an organic halide or alkene or chloralkene is reacted with a hydridochlorosilane in the presence of a quarternary phosphonium salt catalyst by providing sufficient heat to effect a dehydrohalogenative coupling reaction and/or a hydrosilylation reaction and venting the reaction to control reaction pressure and to remove gaseous byproducts from the reaction. The processes are preferably continuous using a catalyst in fluid form at reaction pressures not exceeding about 600 psi. The reactions may be carried out substantially isothermally and/or isobarically, for example in a plug flow reactor or continuous stirred tank reactor. The processes may produce novel silylated compounds including 1,2-bis(trichlorosilyl)decane or 1,2-bis(trimethoxysilyl)decane.
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Page/Page column 3; 6
(2010/02/10)
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