Anisotropic dielectric tensor for chiral polyfluorene at optical frequencies.

The anisotropic dielectric tensor of chiral poly[9,9-bis((3S)-3,7-dimethyloctyl)-2,7-fluorene] is determined via variable angle spectroscopic ellipsometry and circular dichroism spectroscopy. The uniaxial anisotropy indicates a high in-plane alignment of polymer chains in the thin film. Chirality of the polymer results in small but nonzero off-diagonal matrix elements in the dielectric tensor, indicating a helical interchain organization in the vertical direction. This method for determining the dielectric tensor appears to be self-consistent when checked against various theoretical models for the optical activity in the reflection of light. The dielectric constants for the chiral polyfluorene are compared to those for an achiral polyfluorene.