Hyperbranched Conjugated Polymers: Postfunctionalization

In this contribution, the synthesis of two different hyperbranched poly(phenylene vinylene-phenylene ethynylene) (HB-PPV-PPE, 3a−b) scaffolds are reported. The necessary AB2 monomer 2 is obtained by an asymmetric Horner reaction and contains two iodine substituents and one ethynyl group. This AB2 monomer provides, after Sonogashira polymerization, a hyperbranched conjugated polymer decorated with iodine groups, suitable to be further functionalized with terminal alkynes 4a−t by a Pd-catalyzed coupling. Elemental analysis of the postfunctionalized polymers 5a−t and 6a−q reveals nearly complete substitution of the iodine groups. As a consequence of the replacement, substantial increases in fluorescence quantum yields as well as variation in the optical response of the new polymers are observed. The spectroscopic properties of the postfunctionalized polymers were investigated in solution and in the solid state. The emission of the formed hyperbranched polymers shows a strong dependence on the functional groups attached to the conjugated structure and ranges from 510 nm for 5a to 602 nm for 6h. In all cases, solid-state emission is surprisingly strong and red-shifted compared with emission observed in solution.