The Effect of Intrinsic Rigidity on the Optical Properties of PPV Derivatives

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Abstract
Light scattering and optical spectroscopy experiments were performed on [2-methoxy, 5-(2′-ethyl-hexyloxy-p-phenylene-vinylene](MEH-PPV), poly[2-butoxy, 5-(2′-ethyl-hexyloxy-p-phenylene-vinylene](BEH-PPV), and poly[2-dicholestanoxy-p-phenylene-vinylene](BCHA-PPV) in solution with p-xylene to determine the effects of side chain size on the structure and optical properties of PPV. We find that increasing the size of the solubilizing side chains increases the intrinsic persistence length 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-PPV 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 increase in non-radiative decay at high energies when the backbone is more flexible.