The photoluminescence band we assign to the CN backbone protonated at the triazine moiety at 330 nm is blue-shifted in respect to the emission of PTI-IF at 370 nm (Figure ). The changes in the optical spectra coincide with the observation of an equivalence point at pH 5 in the HCl titration of PTI-LiBr dispersions (Figure ). The pKb extracted from the titration is pKb=6.4. The pKa value associated with the conjugated acid is 7.6 (pKa=14-pKb). The conjugated acid is weaker than the conjugated acid of melamin (pKa=5.0). This indicates that the protonated PTI-LiBr structure is better stabilized than the triazinecontaining monomer, presumably due to conjugation across the PTI-backbone (Figure ). The observed optical states are summarised in Figure and compared to the optical gaps predicted by the DFT calculations. Photoconductor experiments using PTI-LiBr were realised on interdigitated indium tin oxide substrates (Figure ). The conductivity of the material is 4 10 -10 S cm -1 in the dark and 1.0 10 -9 S cm -1 in the illuminated state (at 375 nm).