Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Photophysical, Thermal and Structural Properties of Thiophene and Benzodithiophene-Based Copolymers Synthesized by Direct Arylation Polycondensation Method

Version 1 : Received: 28 February 2021 / Approved: 2 March 2021 / Online: 2 March 2021 (21:36:19 CET)

A peer-reviewed article of this Preprint also exists.

Tegegne, N.A.; Abdissa, Z.; Mammo, W. Photophysical, Thermal and Structural Properties of Thiophene and Benzodithiophene-Based Copolymers Synthesized by Direct Arylation Polycondensation Method. Polymers 2021, 13, 1151. Tegegne, N.A.; Abdissa, Z.; Mammo, W. Photophysical, Thermal and Structural Properties of Thiophene and Benzodithiophene-Based Copolymers Synthesized by Direct Arylation Polycondensation Method. Polymers 2021, 13, 1151.

Journal reference: Polymers 2021, 13, 1151
DOI: 10.3390/polym13071151

Abstract

Three low band gap copolymers based on isoindigo acceptor units were designed and successfully synthesized by direct arylation polycondensation method. Two of them were benzodithiophene(BDT)-isoindigo copolymers (PBDTI-OD and PBDTI-DT) with 2-octlydodecyl(OD) and 2-decyltetradecyl (DT) substituted isoindigo units, respectively. Thiophene donor and DT-substituted isoindigo acceptor units were copolymerized to synthesize PTI-DT. The copolymers have broad absorption range that extends to over 760 nm with a band gap ~ .5 eV. The photophysical property studies showed the BDT based copolymers have non-polar ground states. Their emission exhibited the population of intramolecular charge transfer (ICT) state in polar solvents and tightly bound excitonic state in non-polar solvents due to self-aggregation. On the contrary, the emission from the thiophene based copolymers was only from the tightly bound excitonic state. The thermal decomposition temperature of the copolymers was above 380 oC. The X-ray diffraction pattern of the three copolymers showed a halo due pi-pi stacking. A second sharper peak was observed in the BDT-based copolymer with longer side chain on the isoindigo unit (PBDTI-DT) and the thiophene based copolymers with PTI-DT exhibiting a better structural order.

Subject Areas

Intramolecular charge transfer; copolymers; pi-pi stacking; direct arylation polycondensation; excitonic state

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