Study of the Structural and Electronic Properties of Pure Polymer Polypyrrole (PPy) and Doping with TiO2 and ZnO

Abstract

Polypyrrole (PPy) is among the most widely used materials in many different sectors due to its electrical, optical, and mechanical properties. This work presents a study of pyrrole polymer structural and electronic properties pre- and post-doping with ZnO and TiO₂, which were investigated by performing computational calculations based on density functional theory (DFT).  Interpreting theoretical vibrational spectra and finding important information about chemical bonds, functional groups, molecular structures, natural bond orbitals (NBOs), the HOMO-LUMO energy gap, density of states (DOS), and Nuclear magnetic resonance (NMR). The results exhibit functional groups present for the three structures: N-H, O-H, and C-H. The frequency of N-H increased after adding ZnO, and the frequency was greater when adding TiO₂, while the C-H stretching frequency showed a gradual increase consistent with the structures studied. The theoretically calculated energy gap was (3.865 eV) for PPy and (3.2734 eV) for PPy/ZnO, while (3.3235 eV) belongs to PPy/TiO2. Furthermore, the natural bond orbital analysis revealed that PPy/TiO2 had the highest energy among the three compounds (45.14) kcal/mol, indicating a stronger interaction between the donor and acceptor orbitals. The study found that the addition of TiO₂ and ZnO to (PPy) contributed to significant improvements in electrical conductivity, thermal stability, and electrochemical performance. This helps to improve applications in various fields, such as sensors and supercapacitors.