A highly luminescent poly[(m-phenylenevinylene)-alt-(p-phenylenevinylene)] with defined conjugation length and improved solubility

A derivative of poly[(m-phenylenevinylene)-alt-(p-phenylenevinylene)] (7) has been synthesized via the standard Wittig condensation to investigate the effects of m-phenylene on the physical properties of PPVs. The polymer synthesized has a molecular weight of about 20 000, corresponding to a number-average degree of polymerization of about 41. A model compound, 1,4-distyryl-2,5-dihexyloxy-benzene (9), has also been synthesized to evaluate the effectiveness of pi-conjugation interruption at m-phenylene. Comparison of photoabsorption and emission characteristics between 7 and 9 indicates that the presence of m-phenylene effectively interrupts the conjugation in PPV, allowing precise color control in the fully pi-conjugated polymers. H-1 NMR is found to be a convenient tool to characterize the cis/trans-olefins in the polymer. The PL quantum yield of 7 is quite high in both solution and solid states (0.6-0.8), suggesting potential applications of the material in various electrooptical devices.