New microstructured chromium doped poly(p‐toluidine) as a new acid–base indicator and precursor for chromic oxide nanostructured

New chromium doped poly(p‐toluidine) (Cr‐PPT) was synthesized via chemical oxidative polymerization of p‐toluidine with potassium dichromate as an initiator in acidic aqueous medium. The spectrophotometric behavior of Cr‐PPT in acetone and chloroform as different solvents was investigated. Cr‐PPT exhibits bathochromically red shift at 46‐nm value with the increasing of solvent polarity. The intermolecular charge transfer band peak for Cr‐PPT shifted from 422 nm in low‐polar solvent (chloroform) to high‐polar solvent (acetone) to 468 nm. Optical absorption measurements are used to obtain the energy gap of prepared Cr‐PPT. Cr‐PPT has an optical band gap (E_g = 1.90 to 2.05 eV) that is located in the semiconductor range. Pink color was observed using Cr‐PPT solution in acidic media while it changes sharply to yellow in basic medium. Based on intermolecular charge transfer, the Cr‐PPT was used as acid–base indicator. Cr‐PPT and phenolphthalein (phph) indicator were used for determination of normality of HCl using standard 0.1 N NaOH, the two indicators gave equal end point values. Using Cr‐PPT as a new molecular precursor for the production chromium oxide in nanoscale by thermal decomposition route was studied, and the average size of synthesized Cr₂O₃ was found in the range of 54–61 nm. Copyright © 2017 John Wiley & Sons, Ltd.