Self-assembly of poly(p-phenylene vinylene) using long chain counter-ion: a new process for fabrication of multilayer thin films heterostructures.

Layer-by-layer thin films of sulfoniun poly(p-phenylene vinylene) (PPV) pre cursor have been processed using the long chain dodecylbenzenesulfonate (DB S) anion. Here we adopted the alternative approach consisting of the contro lled substitution of the chloride counterion of a water-soluble PPV precurs or by DBS. The internal layer structure of these films is therefore likely to be different from conventional layer-by-layer films, since DBS ions are expected to be incorporated into the PPV precursor chain. The main advantag e of this novel procedure is that thermal conversion through the eliminatio n of DBS may be realized at considerably lower temperatures (80-100 OC) in a few minutes, with enhanced optical properties. Using this new conversion procedure, the conjugation length can also be varied along the deposition d irection by controlling the immersion time or DBS concentration in the film . This opens up a number of new possibilities to realize molecularly band-g ap engineered structures such as asymmetric ladder type or "V-type" structu res along the film.