A study of the different structural phases of the polymer poly(9,9 '-dioctyl fluorene) using Raman spectroscopy

The polymer poly(9,9'-dioctyl fluorene) (F8) can be easily driven between a number of different structural phases by different thermal or solvent trea tments. The phases which we have identified include (i) as-spin-coated, (ii ) semi-crystalline, (iii) glassy, (iv) with an extended intrachain conforma tion. Atomic force microscopy has been used to investigate the surface stru ctures associated with the different phases of the polymer and different so lvents used to cast the film. Raman spectroscopy has been performed on thes e samples to understand how the polymer conformation changes with the phase s. Variations in the relative intensity of the peaks and shifts in energy a re observed. We have compared the Fs spectrum with a trimer of fluorene wit h butyl side chains and acrylate/hydroxy endgroups attached to the fluorene main chain via hexyl spacers. We identify a very small frequency dispersio n in the vibrational modes connected to an increase of the conjugation leng th. Therefore, the assignment of the vibrational modes of the trimer is ver y important for understanding the F8 spectrum. (C) 2001 Elsevier Science B. V. All rights reserved.