THE EFFECT OF INTRINSIC RIGIDITY ON THE OPTICAL-PROPERTIES OF PPV DERIVATIVES

Light scattering and optical spectroscopy experiments were performed o n [2-methoxy, 5-(2'-ethyl-hexyloxy-p-phenylene-vinylene] (MEH-PPV), po ly[2-butoxy, 5-(2'-ethyl-hexyloxy-p-phenylene-vinylene] (BEH-PPV), and poly[2-dicholestanoxy-p-phenylene-vinylene] (BCHA-PPV) in solution wi th p-xylene to determine the effects of side chain size on the structu re and optical properties of PPV. We find that increasing the size of the solubilizing side chains increases the intrinsic persistence lengt h of the PPV backbone and this change in rigidity has dramatic effects on the photoluminescence of PPV. Quantum yield determination relative to Rhodamine 6G shows the luminescence efficiency of the rigid BCHA-P PV is 0.66 +/- 0.05 and that the yield decreases to 0.20 +/- 0.05 for MEH-PPV, the most coiled derivative. Excitation profiles show an incre ase in non-radiative decay at high energies when the backbone is more flexible.