Influence of film morphology on the vibrational spectra of dioctyl substituted polyfluorene (PFO)

Raman spectroscopy has been performed on samples of dioctyl substituted polyfluorene (PFO) with four morphologies: (i) as spin-coated, (ii) crystalline, (iii) glassy, (iv) prepared so as to contain a fraction of material with an intra-chain ordered conformation. The different morphologies were thermally induced in films spin-coated from solutions of PFO in tetrahydrofuran, chloroform and cyclohexane on aluminium, silicon and quartz substrates. There are no differences in the Raman spectra measurement for the glassy and spin-coated samples. The spectra of the samples with the intra-chain ordered state and in the crystalline phase show shifts in positions and linewidths of the Raman peaks. The vibrational modes are identified by reference to published spectra for both model compounds and related phenylene-based polymers.