Syntheses and characterization of benzimidazole containing polymers: a comparative study on donor unit effect and influence of H-bonding

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2013
Nurioğlu, Ayda Gökçek
The first part of this work reports a comparative study on electrochromic properties of two Donor-Acceptor-Donor (DAD) type polymers, namely poly(2-heptyl-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole) (BImTh) and poly(4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-heptyl-1H-benzo[d]imidazole) (BImEd). DAD type polymers are designed to bear the same acceptor unit, benzimidazole and two different donor units, thiophene and 3,4-ethylenedioxy thiophene (EDOT) to make a comparison based on the donor unit effect. The resulting polymers are both multichromic and have low band gap values (1.93 eV for PBImTh and 1.74 eV for PBImEd). In the second part, 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-phenyl-1H-benzo[d]imidazole (BImBEd) is synthesized. In order to figure out the presence of an intramolecular hydrogen bonding between the amine bond of the imidazole ring and the oxygen of the EDOT molecule, different amounts of trifluoroacetic acid (TFA) and concentrated sodium hydroxide (NaOH) solutions were added during electrochemical polymerization. These treatments caused protonation of the imine and deprotonation of the amine bonds respectively. In order to prove the changes in the optical properties of the polymers due to different number of protonated and deprotonated imine and amine bonds, 1,4-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)benzene (BEDOT-B) was also synthesized and treated with the same procedures. Results showed that it is possible to control the main chain conformation of even an insoluble polymer via acid and base treatments during in situ polymerization.
Citation Formats
A. G. Nurioğlu, “Syntheses and characterization of benzimidazole containing polymers: a comparative study on donor unit effect and influence of H-bonding,” M.S. - Master of Science, Middle East Technical University, 2013.