Semi-empirical computation of molecular properties affecting the electrical conductivity of polyaniline and polypyrrole as influenced by doping

Date

10-2003

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Ernesto J Del Rosario

Abstract

PASCUAL, ABIGAIL A. University of the Philippines at Los Banos, October 2003. Semi-empirical Computation of Molecular Properties Affecting the Electrical Conductivity of Polyaniline and Polypyrrole as Influenced by Doping.

Adviser: Dr. Ernesto J. del Rosario

Semi-empirical computation on polyaniline (PANI) and polypyrrole (PPY) was done in order to determine the molecular properties that affect the electrical conductivity during doping or addition of charge carriers to the polymer. After geometry optimization, computation was done on the PAM bases (leucoemeraldine, emeraldine, and pernigraniline) and doped PAM, as well as on undoped, partially doped, and fully doped PPY, using the PM3 method within the HyperChem 7.0 software.

It was found that doping in polyaniline lowered the HOMO and LUMO orbital energies and the energy gap, and increased the bandwidth of unoccupied orbitals. Ionization potential, electron affinity, total dipole moment, heat of formation and mean polarizability also increased after doping of PAN!. The charge sign alternation of the partial charges for the ring (partial negative charge) and N (partial positive charge) was more pronounced for the doped PAM, such that the positive charges on N had higher values.

Increasing the doping level in PPY from partial to full lowered the HOMO and LUMO energies, and increased the ionization potential, electron affinity, heat of formation, and mean polarizability. The total dipole moment of PPY showed an increase from the undoped to the partially doped and a decrease when the polymer was fully doped.The partial charge distribution showed a dramatic alternation per ring basis for the fully doped polymer.

Generally, the molecular properties that were observed to be affected by doping are the FMO energies, energy gap, bandwidth, ionization potential, electron affinity, total dipole moment, heat of formation, mean polarizability, and partial charge distribution. A higher conductivity was correlated with lower energy gap, greater bandwidth of conduction band, higher total dipole moment, higher mean polarizability, and alternating positive and negative charges along the polymer chain.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2003 C4 P37

Document Type

Thesis

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