Control of conjugation length and enhancement of fluorescence efficiency of poly(p-phenylenevinylene)s via post-halogenation

Post-functionalization of poly(p-2,5-dihexyloxy-phenyelenevinylene) (DHO-PPV) was studied using N-bromosuccinimide (NBS) and N-chlorosuccinimide (NCS) in CHCl3 and CHCl3/AcOH to control the color of fluorescence emission and to enhance emission efficiency. It was found that in addition to electrophilic substitution on phenylene rings, halogen and succinimide (in CHCl3) and acetate groups (in CHCl3/AcOH) add across the main chain vinylene groups. With low NXS/PPV reaction ratios (0.1-0.35), where X = Br or Cl, the resulting polymers show poor solubility, a red shift of the absorption maximum, and a decrease in the solid-state fluorescence efficiency (Phi(fl)), which are explained on the basis of enhanced interchain interactions. For NXS/PPV reaction ratios between 0.5 and 0.75, the solubility of polymers was significantly improved and Phi(fl) was enhanced by up to 150% due to exciton confinement and a reduction in chain aggregation. For NXS/PPV reaction ratios >0.75, Phi(fl) decreased dramatically because of an increasing loss of pi-conjugation.

Chemistry of Materials

Chemistry of Materials

14

1520-5002

N/A

3

6