Fluorenes crosslinking

Dicyanates react with diisocyanates. The poly addition results in the formation of crosslinked polymers with cyanurate and isocyanurate rings [32]. The polymers have high deformation and decomposition temperature in the case of a crosslinked copolymer from 9,9-bis(4-cyanatophenyl)fluorene the corresponding values are 480 °C and 440 °C (in air), respectively. 

By subsequent deposition of crosslinked hole conductors with increasing redox potential, so-called electronic stairs can easily be fabricated. Those electronic stairs , introduced underneath HTLs between the anode and an endcapped poly-fluorene derivative lead to an increase in efficiency by a factor of three [40]. 

The first oxetane-functionalized emitter were pyrene derivatives (Fig. 9.19(b), [46]), however, with very limited performance in OLEDs. Later, a poly(pheny-lene-fluorene)-copolymer was reported, however, without any electroluminescence data (Fig. 9.19(c), [47]). The breakthrough came with a recent report on a crosslinkable class of state-of-the-art spirofluorenes (Fig. 9.19(a), [48, 49]). By incorporating a green- and red-emitting comonomer, it was possible to generate the three primary colors (RGB) necessary for color-display applications. More recent concepts use sterically hindered 9,9 -diarylfluorene blocks to link conjugated oligomers (Fig. 9.19(d), [50]). 

To this point the effect ofthermoplastics on DGEBA or TGAP,di- andtri-fimctional epoxies, has been discussed. However, when epoxies are reinforced with fibers to form polymer composites for use as structural materials, atetra-2,3-epoxypropyl epoxy is frequently used because its greater crosslinking provides a more damage tolerant epoxy. Other special epoxies such as the 2,3-epo qjropyl ether of bis(hydroxy )fluorene are of interest as well. 

Researchers at the University of Hull undertook comparisons between model liquid crystalline compounds and related reactive mesogens, which form nematic mesophases using two different conjugated cores containing the fluorene moiety, see Chaps. 7 and 8. In one study, based on a biphenyl-bithiophene-fluorene(compound HI), core time of flight measurements were carried out in the nematic phase of the model compound, the nematic phase of the diene substituted RM and on the crosslinked compound at room temperature [34], They found a large drop in hole mobility between the model compound and the nematic phase of the RM from 8 X 10 " to 1.5 X 10 cm s There was a small recovery in hole mobility... 

Fig. 7. 16 Top Chemical structures of crosslinkable fluorene oligomers. Bottom. Fluorescence microscope (left) [46] and SEM image (right) of a microstructured oligofluorene [62]...

---