Investigation of the correlation between chemical structure and morphology in oligoaniline microspheres produced in buffered conditions

Although the mainly intermolecular forces involved in the self-assembly of oligoaniline molecules have been consistently discussed (hydrogen bonds and pi-pi stacking interactions) the correlation between the driving forces and the large variations of morphology that can be obtained is still open in discussion, mostly because a detailed chemical characterization of such products is usually difficult to achieve. In this work, 3-D fluorescence spectroscopy is presented as a powerful technique in the identification and differentiation of phenazinic segments, with Raman spectroscopy being crucial for identification of 1,4-Michael-type segments and the verification of non-hydrolyzed imine groups in oligoaniline microspheres produced under pH 4.5 buffered conditions and employing different reagent concentrations. The results suggested that the self-assembly must occur by hydrogen bonds related to the non-hydrolyzed iminic groups and pi-pi stacking interactions between non-substituted phenazinic segments. Moreover, obtaining specific morphologies (flower-like structures, porous microspheres and hollow microspheres) showed dependence with the increase of the relative reagent concentrations.