New conjugated poly(ketanil)s, i.e. polymers containing ketimine groups in their main chain, have been synthesized from 1,4-phenylenediamine (or benzidine) and five different diketones via polycondensation with the goal to obtain new materials of tunable luminescent properties. It is demonstrated that both the absorption and photoluminescence spectra can be modified not only by changing the ratio of conjugated to non-conjugated segment in the polymer main chain but also via acid-base doping involving the protonation of ketimine groups. By combining these two methods, it is possible to precisely tune the emission spectra of poly(ketanil)s in the spectral range of 520-580 nm. The use of bifunctional protonating agents, containing plasticizing groups, for example 1,2-(di-2-ethylhexyl)ester of 4-sulfophthalic acid (DEREPSA), in addition to the modification of the luminescent spectra, leads to a lowering of the glass transition temperature (T-g) of the polymers studied by approximately 100-150 K. Thus, the majority of the polymers studied exhibit, in their doped state, the T-g below room temperature leading to flexible films of good mechanical properties. (C) 2003 Elsevier B.V. All rights reserved.