In situ Characterization of Phase Transition of Amorphous Poly(9,9-di-n-octyl-2,7-fluorene)Thin Film During Thermal Annealing

摘要

Amorphous poly(9,9-di-n-octyl-2,7-fluorene)(PFO)thin films were characterized in situ via thermal an- nealing based on grazing incidence X-ray diffraction(GIXRD)profiles,UV-visible absorption spectrophotometry,and Fourier transform infrared spectroscopy(FTIR).The results of GIXRD indicated that the amorphous phase transformed into a crystalline phase when the annealing temperature was higher than 80 ℃.Different outcomes were elicited for the intensities and d-spacings of the diffraction peaks below and above 80 ℃,which were attributed to the formation of the κ-phase.The mechanism of phase transition was revealed by in situ UV-visible absorption and FTIR spectra,whereby the rearrangement of the side chains was dominant and the movement of the main chains was minimal,even when the annealing temperature was lower than 80 ℃.In contrast,the rearrangement of the main chains was dominant when the temperature was higher than 80 ℃.