Characterizations Stability and Phase Behavior

Generally, fluorene homo- and copolymers show excellent thermal stability the Tdec of many PF exceeds 400°C (according to thermogravimetric analysis (TGA) analysis under inert atmosphere) [224]. 

Whereas poly(9,9-dihexylfluorene) (PDHF, 195) is generally considered as amorphous, PF with longer octyl side chains, PFO 196, is crystalline material. Many PFs — dioctyl (PFO 196 [228,230,231]) or 2-ethyl hexyl) (197 [232]) as well as some fluorene copolymers [233] exhibit liquid crystalline behavior, opening a possibility to fabricate polarized LEDs [224,234,235] (Chart 2.45). 

FIGURE 2.8 XRD powder pattern of highly crystalline thick-film PFO 196 specimen after extended heat treatments at elevated temperatures and stepwise cooled to room temperature. (From Chen, S.H., Chou, H.L., Su, A.C., and Chen, S.A., Macromolecules, 37, 6833, 2004. With permission.) 

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