Cross-linkable Polymers Based on Dialkylfluorenes

We have prepared a series of cross-linkable oligo- and poly(dialkylfluorene)s by nickel(0)-mediated polymerization of 2,7-dibromo-9,9-dialkylfluorene (alkyl = n-hexyl) and 4-bromostyrene. The resulting fully soluble and processable, styryl-functionalized oligomers and polymers can be cross-linked via the vinyl end-groups by curing at 175−200 °C, consistent with the autopolymerization mechanism of styrene. These relatively mild conditions render the materials insoluble and enable multilayering of polymers in organic light emitting devices. At the same time, the electrical and/or optical properties of the cross-linked polymers are preserved and no deleterious species or undesirable byproducts are produced. Furthermore, the cross-linking allows control of the supramolecular ordering of the planarized rigid rod-type fluorene segments in the polymer backbone that leads to suppression of troublesome excimer/aggregate in the photo- and electrolumenescence.