We have measured the photoluminescence quantum yield and photoluminescence lifetime for a series of polythiophenes, in solution, and the quantum yield for the same polymers in thin films. Depending on the different substituents, quantum yields ranged between 0.38 and 0.01 for polymers dissolved in chloroform; for spin-coated films, quantum yields as high as 0.24 were measured. We observe that increasing the bulkiness of the substituent increases the quantum yield in solution. For spin-coated films an increased ordering can either increase or decrease the quantum yield, depending on the separation of the conjugated backbones. Polythiophenes in which the electronic band gap is increased by steric hindrance show very low quantum yield, both for film and solution. This low quantum yield originates from a fast nonradiative decay.

New solution processing systems were studied with the goal to obtain highly conductive polyaniline films with good mechanical properties and its conducting blends with poly(methyl methacrylate). A new dopant, namely, 1,2-benzenedicarboxylic acid, 4-sulfo, 1,2-di(2-ethylhexyl) ester (DEHEPSA), was studied as a protonating agent. It was found that the use of this dopant together with dichloroacetic acid (DCAA) or difluorochloroacetic acid (DFCAA) as solvents leads to films showing conductivities of 180 and 100 S/cm, respectively. Films cast from DCAA are metallic in character down to 220 K. Since the protonation agent used exhibits doping as well as plasticizing properties, the resulting polyaniline films, in addition to high conductivity, show excellent flexibility and much lower glass-transition temperature, T g, (280 K) as compared to polyaniline doped with other protonating agents. Moreover, the same processing system can be used for the fabrication of polyaniline-poly(methyl methacrylate) blends with low percolation threshold (much below 1 wt % of PANI). Upon casting, the overwhelming majority of the solvent can be efficiently removed from the polymer matrix, whereas the remaining residual solvent is strongly bound to the polymer matrix. For this reason, the resulting blends do not show the disadvantages of the blends cast from m-cresol which release the residual solvent upon aging.