Chain morphologies in semicrystalline polyfluorene: evidence from Raman scattering.

The beta phase in di-octyl substituted polyfluorene (PF8) exhibits a surprising level of conformational order at nanometer length scales compared to other phases. We present Raman scattering studies of PF8 as a function of thermal cycling, which establishes a connection between the conformational isomers and the side and main chain morphology. Density-functional calculations of the vibrational spectra of single chain oligomers in conjunction with the experimental results demonstrate the incompatibility of the beta phase with the overall alpha crystalline phase in PF8.