Poly diarylfluorene s

In contrast the materials 47 with di-ferf-butylphenyl and 48 with first generation dendron side-chains were processable from toluene [73]. The degrees of polymerisation for these polymers were rather low, with the den-dronized polymer 48 having a Mn of only lOOOOg/mol (n = 10) probably due to the bulkiness of the substituents. Polymer 48 was also found to be exceptionally thermally stable, with no significant mass loss being observed in thermal gravimetric analysis (TGA) until 570 °C (cf. 463 °C for 89 [73]). 

One effect of aryl substituents on the physical properties of polyfluorenes is to inhibit chain packing as demonstrated by the lack of liquid crystalline 

---

Spirobifluorenes have been investigated by Salbeck [100] and found to be promising materials for use in blue LEDs, and so some effort has been made to incorporate these units into polymers (Scheme 30). As poly(diarylfluorene)s have proven to be stable blue emitters it comes as no surprise to find that polymers containing spirobifluorenes such as 66 [101] and 67 [102] also produce stable blue emission. A fluorene-spirobifluorene alternating copolymer 68 has been made and was found to give stabler emission than the fluorene homopolymer 16, but green emission was still observed upon heating in air at 150 °C [103]. 

---