Ab initio study of ladder-type polymers: Polythiophene and polypyrrole

Abstract

This article presents an ab initio study of four polymers, polythiophene, polypyrrole, ladder-type polythiophene, and ladder-type polypyrrole. Upon an analysis of the variation of the band gap when comparing the unconstrained and the ladder-type polymers, a discrepancy was found between the thiophene and the pyrrole polymer families. For polythiophene, the ladder-type polymer has a larger gap than the unconstrained polymer whereas the opposite is found for the pyrrole polymers. The structural properties and the charge densities using the Bader charge analysis of these four compounds are investigated. The different band gap behaviors in thiophene and pyrrole polymers can be explained in terms of the competition between the bond length alternation and the effect of the charge density in the carbon backbone.

First principles elaboration of low band gap ladder-type polymers

“…More details about the electronic properties of that latter polymer can be found in a previous study. 23 The four other ladder-type polya͒ Electronic mail: michel.cote@umontreal.ca. mers considered are based on this atomic structure.…”

“…A deeper study of the electronic properties of LPT and LPPy and their nonladder configurations using different basis sets and functionals has been reported in a previous article. 23 Considering first the LPT band structure, the minimum energy gap is found at ⌫ with a value of 1.58 eV. Note that this is a LDA value, and it is likely to strongly underestimate the real energy gap and does not take into account the excitonic effect.…”

1,4‐Dihydropyrrolo[3,2‐b]pyrrole and Its π‐Expanded Analogues

“…[25] The synthesis of conducting polymers possessing enhanced stability is a very important goal, and polythiophenes [26] and polypyrroles [27] have often been investigated in this regard. [29] DFT calculations suggested that such polymers were characterized by a small distance between the valence band and the conduction band (i.e., band gap). Oyama and co-workers performed electropolymerization of 1 and some of its simple derivatives.…”

“…They decided to follow theoretical investigations to prove that ladder-type compounds had less conformational freedom than that of polyenes. [29] DFT calculations suggested that such polymers were characterized by a small distance between the valence band and the conduction band (i.e., band gap). This phenomenon probably arises from the polymers planar structure, which causes more effective overlap of the p orbitals, and hence, more efficient conduction of charge along the polymer chain.…”

A theoretical investigation on the properties of the new poly(N‐vinylcarbazole)‐3‐methylthiophene (PVK‐3MeT) synthesized graft copolymer

“…The molecular quantum chemical calculations were performed essentially using the framework of the Kohn‐Shan Density Functional Theory (DFT)14 implemented in the Gaussian 03 program package 15. All calculations on the studied oligomer of this work were done on cluster machines in the CCIPL (Intensive Computing center at the University of Nantes (Pays de la loire)).…”