Ordering of Single Conjugated Polymers in a Nematic Liquid Crystal Host

We describe molecule-by-molecule observations, using single molecule fluorescence spectroscopy, of the ordering of the components in a nematic phase formed by a binary mixture of short and long rods. A stiff conjugated polymer, MEH-PPV (poly[2-methoxy-5-((2-ethylhexyl)oxy)-l,4-phenylenevinylene]), present at very low concentrations in a binary nematic - nematic phase with the mesogen 5CB (4-n-pentyl-4′-cyanobiphenyl) is investigated. We observe near-perfect orientational order of the stiff, rodlike conjugated polymers translating through a planar nematic phase. This represents striking experimental evidence for the predicted enhanced alignment of long rods in the nematic phase of a binary mixture of rods.