Enhanced optical properties of layer-by-layer films of poly(p-phenylenevinylene) alternated with a long chain counterion and converted at low temperatures

Layer-by-layer (LBL) thin films of a poly(p-phenylenevinylene) (PPV) precursor have been processed using the long chain dodecylbenzenesulfonate anion (DBS). We adopted the alternative approach with controlled substitution of the chloride counterion of the water-soluble PPV precursor by DBS. The internal layer structure of these films is likely to be different from conventional LBL films, since DBS is incorporated into the PPV precursor chain. In addition to the fast adsorption of the sulfonic salt, introducing DBS allows the films to be converted at 110 degreesC within 12 min with a high conjugation length. By varying the amount of DBS in the solution, the conjugation length of the PPV segments can be controlled. The luminescence and absorption spectra show intense vibronic structures that are better resolved than for cast and Langmuir-Blodgett films of PPV. LBL films converted at lower temperatures display higher quantum efficiency, owing to the absence of carbonyl groups arising from high-temperature conversion procedures.