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

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 a broad absorption range that extends to over 760 nm with a band gap ≈1.5 eV. The photophysical property studies showed that the BDT-based copolymers have non-polar ground states. Their emission exhibited the population of the 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 °C. The X-ray diffraction pattern of the three copolymers showed a halo due to π−π stacking. A second, sharper peak was observed in the BDT-based copolymer with a longer side chain on the isoindigo unit (PBDTI-DT), and the thiophene-based copolymers with PTI-DT, exhibiting a better structural order.

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

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.

Influence of synthetic pathway, molecular weight and side chains on properties of indacenodithiophene-benzothiadiazole copolymers made by direct arylation polycondensation

Poly(indacenodithiophene-alt-benzothiadiazole) with different side chains and molecular weight is made using two different pathways in which all C–C coupling steps are achieved by C–H activation, and the products are comprehensively investigated.

Direct Arylation Polycondensation towards Water/Alcohol-Soluble Conjugated Polymers as Electron Transporting Layers for Organic Solar Cells

Two water/alcohol soluble conjugated polymers (WSCPs), based on naphthalenediimide and amino-functionalized 3,4-(propylenedioxy)thiophene were synthesized via direct arylation polycondensation (DArP). The polymers worked well as electron transporting layers (ETLs) for fullerene-based...

Temperature-dependent morphology-electron mobility correlations of naphthalene diimide-indacenodithiophene copolymers prepared via direct arylation polymerization

A series of defect-free n-type copolymers poly(naphthalene diimide-alt-indacenodithiophene) P(NDI-IDT) comprising alternating naphthalene diimide (NDI) and indacenodithiophene (IDT) units is prepared using atom-economic direct arylation polycondensation (DAP). Copolymers with varying molecular...

Tuning Molar Mass of P3HT via Direct Arylation Polycondensation Yields Optimal Interaction and High Efficiency in Nonfullerene Organic Solar Cells

Due to the simple structure and excellent scalability, regioregular poly(3-hexylthiophene) (P3HT) becomes much popular as a low-cost donor polymer partner with the emerging nonfullerene acceptors in recent years. Presently, the...

Diketopyrrolopyrrole-based conjugated polymers synthesized by direct arylation polycondensation for anisole-processed high mobility organic thin-film transistors

Two conjugated polymers (CPs) Fu-F and Fu-Cl that are soluble in a green solvent anisole were successfully synthesized via direct arylation polycondensation (DArP) using a furan-flanked diketopyrrolopyrrole (DPP) derivative (FDPP-Br)...