Synthesis and optical properties of polynaphthalene derivatives

Naphthalene-base conjugated polymers soluble in organic solvents were newly synthesized, and their optical properties were characterized. Three types of homopolymers were synthesized from 1,4-, 1,5- and 2,6-dibromonaphthalene derivatives by the Ni-catalyzed polycondensation. Alternate naphthalene copolymers with 1,4-phenylene were synthesized by Suzuki coupling. In the photoluminescence (PL) spectra, all polymers emitted bluish purple in CHCl3. Especially, 2,6-polynaphthalene derivatives showed high quantum efficiencies (ϕfl = 0.60–0.96). In the case of thin films, 1,5- and 1,4-linked polynaphthalenes showed PL spectra similar to those in solution, while 2,6-linked polynapthalenes had PL spectra shifted longer in wavelength than the former, which was due to π-interaction of the stacking naphthalene units between the polymer chains.