Comparison of polydipentylsilylenes and -siloxanes containing chiral groups

Polydipentylsilylene and -siloxane copolymers, containing bis[(S)-(+)-2-methylbutyl]silane units have been synthesized. Thermal analysis demonstrated for both types of copolymers that crystallization was hindered on incorporation of the 2-methylbutyl groups. Optical rotation measurements in various solvents yielded a much stronger optical activity of the polysilylene copolymers, compared to the polysiloxanes. This effect has been explained by the formation of a chiral supramolecular structure in the case of the polysilylenes. The measurements have indicated that the solvent quality can be employed to enhance the formation of this structure at relatively low 2-methylbutyl contents.