Synthesis of a novel optically tunable amphiphilic poly(p-phenylene):: Influence of hydrogen bonding and metal complexation on optical properties

A series of optically tunable amphiphilic conjugated polymers, poly(2-hydroxy-5-alkoxy-p-phenylene) (1) containing long alkyl chains, were prepared by Suzuki polycondensation using 2,5-dibromo-1-benzyloxy-4-alkoxybenzene and bis(boronic ester) monomers. All polymers showed good solubility in common organic solvents such as tetrahydrofuran (THF), chloroform, toluene, and dimethylformamide (DMF). Optical properties of all polymers were investigated in TH-F at room temperature under neutral conditions, and emission maxima were observed in the violet region (lambda (emi) = 401-403 nm). By the addition of stoichiometric amount of a base (e.g., aqueous NaOH solution), absorption maxima shifted to the blue region (lambda (emi) = 474-468 nm). The ionochromic effect of target polymers with transition metal ions such as Fe3+, Cu2+, and Co2+ was also reported. In the presence of metal ions, the optical properties of polymers showed interesting tunability of emission maxima, Delta lambda (max) (140-26 nm). X-ray diffraction studies using powdered polymer samples indicated an ordered lamella-type lattice.