The formation of ruptured poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenyl vinylene] (MEH-PPV) thin films coated from undried tetrahydrofuran (THF) solutions was investigated. Because of the incompatibility of water and MEH-PPV, the polymer films coated from THF/water solutions showed a ruptured film structure. In the photoluminescence (PL) spectra of the polymer thin films, the ruptured polymer films showed a redshifted emission in comparison with continuous polymer thin films. According to a comparison of the PL spectra of polymer solutions and films, MEH-PPV in THF showed a coil-cylinder transition during precipitation from solution. Because of the incompatibility of water and MEH-PPV, an increase in the water content could increase the ratio of polymer chains in the cylinder conformation, resulting in a redshifted emission for the films. 0 2005 Wiley Periodicals, Inc.