Functionalised Spirobifluorenes for Photonic Applications


Ana Charas,1 Luísa Mendonça,1 Luís Alcácer,1,2 and Jorge Morgado1,2

1Instituto de Telecomunicações, Instituto Superior Técnico, Avenida Rovisco Pais,
P-1049-001 Lisboa, Portugal; 2Departamento de Engenharia Química e Biológica, Instituto Superior Técnico, Avenida Rovisco Pais, P-1049-001 Lisboa, Portugal.

Plastic optical fibers (POFs) are potential office-and home-network media. Due to their larger core, compared with silica fibers, they allow the use of inexpensive injection-molded plastic connectors and low link costs.
Since Lanzani et al. [1,2] have demonstrated optical gain and ultra-fast switching in a matrix made of the luminescent polymer poly(9,9-dioctylfluorene) dispersed in polymethylmetacrylate (PMMA), in a region where both attenuation and dispersion from PMMA are relatively low, this opened a new area for photonics applications and the prospects for electro-optical switching in polymeric materials. Hence, it is of particular importance to explore and to optimize these potential properties of conjugated luminescent polymers dispersed in inert polymer matrices, for photonic applications, in general, and, in particular, for POFs. This requires the development of new materials. Spiro-linked bifluorenes are attractive materials in this field as they are highly efficient blue emitters [3], have demonstrated amplified spontaneous emission [4], they tipically form vitreous amorphous films (an essential prerequisite for low loss structures), and they are thermally very stable.
Ultra-fast optical switching is thought to be associated to isolated conjugated polymer chains [2]. In order to achieve high load of the conjugated polymer in the PMMA matrix, while maintaining the chains of the conjugated polymer isolated, we have been developing copolymers comprising both spirobifluorene and PMMA blocks, as new media for POF applications. The copolymer approach, in alternative to blends of PMMA and fluorene-based materials, aims at minimizing phase separation between the two different materials. Here, we present the synthesis and characterisation of new spirobifluorene-PMMA copolymers. The synthetic route comprises the bulk copolymerization of MMA monomer with two different spirobifluorene-derivatives functionalised with MMA reactive groups. Several of these materials are characterized in terms of their optical properties.


This work was partially supported by EU under contract FP6-026365 (POLYCOM).

References

[1] T. Virgili, D. Marinotto, G. Lanzani, and D.D. C. Bradley, Applied Physics Letters 86, 91113 (2005).
[2] T. Virgili, D. Marinotto, C. Manzoni, G. Cerullo, and G. Lanzani, Phys. Rev. Lett. 94, 117402 (2005).
[3] K. Wong, Y. Chien, R. Chen, C. Wang, Y. Lin, H. Chiang, P. Hsieh, C. Wu, C. H. Chou, Y. O. Su, G. Lee, and S. Peng, Journal of American Chemical Society 124, 11576 (2002).
[4] T. Spehr, A. Siebert, T. Fuhrmann-Lieker, J. Salbeck, T. Rabe, T. Riedl, H. H. Johannes, W. Kowalsky, J. Wang, T. Weimann, and P. Hinze, Applied Physics Letters 87, 161103 (2005).