Diketo-Pyrrolo Pyrrole-Based Acceptor-Acceptor Copolymers with Deep HOMO and LUMO Levels Absorbing in the Near Infrared

Round 1

Reviewer 1 Report

Electronic levels of polymers are of interests, because, as auhtors mentioned, these materials can be used in solar cells design.

Both theoretical and experimental data were used here, which make this paper interesting to read.

I recommend publishing after only cosmetics corrections (use similar format of graphs, correction of misprints,...)

Author Response

We sincerely thank the reviewer for the positive comments on our submission. Some changes have been through the main text and fonts have been made uniform in figures.

We hope this version will match your requirements.

Reviewer 2 Report

Khelifi et al. reported four acceptor-acceptor (A-A’) alternated copolymers based on DPP. UV-visible spectrophotometry and cyclic voltammetry show large absorption range differences as well as HOMOs/LUMOs. This is interesting for future molecular design for low bandgap polymers. This paper can be accepted after revisions.

1. For UV-vis. Absorption spectra, P(DPP-DPPeH) showed blue shift of absorption maxima of 74 nm for solution and solid states, while P(DPP-DPPC12) showed red shift of 47 nm. This difference should be due to the poor thin film formation of P(DPP-DPPeH). The authors should remeasure the thin film absorption of P(DPP-DPPeH) by optimizing the condition either by drop casting or spin coating.
2. Why did P(DPP-DAP) show differences in TGA curves (Figure 6)? Is it because of the instability of monomer DAP? The author should comment on it.
3. The cited references were too old. New references for recent three years should be cited. For example, for DPP in this paper, new references about opto/electronic studies should be cieted, such as Adv. Mater., 2020, 32, 1903882; Org. Chem. Front 2021, 8, 4560; J. Phys. Chem. Lett. 2022, 13, 1131.
4. Diketo-pyrrolo pyrrole means the center unit, but not include the flanked thiophene of it. Since the aromatic group flanked by DPP can be benzene, thiophene, selenophene etc. The author should point out what they used in this paper is thiophene-flanked DPP.

 

Author Response

The authors thank the reviewer for the relevant questions/comments. You will find below our answers.

1. For UV-vis. Absorption spectra, P(DPP-DPPeH) showed blue shift of absorption maxima of 74 nm for solution and solid states, while P(DPP-DPPC12) showed red shift of 47 nm. This difference should be due to the poor thin film formation of P(DPP-DPPeH). The authors should remeasure the thin film absorption of P(DPP-DPPeH) by optimizing the condition either by drop casting or spin coating.

We thank the reviewer for this relevant comment. This is probably the reason, branched chains present at every unit in this copolymer may hinder the packing when going from solution to the solid state. Unfortunately, it is not possible to remeasure the spectrum as we are out of this sample. We added a comment on it and modified the text from lines 296 to 299.

1. Why did P(DPP-DAP) show differences in TGA curves (Figure 6)? Is it because of the instability of monomer DAP? The author should comment on it.

Yes, we agree with you. We assume that this early degradation is due to a lack of the ethylhexyl chains connected to sulfur atom in the DAP unit. Indeed, the theoritical weight percentage of these chains of DAP compared to the repeating unit DPP-DAP is 21%, which is in agreement with 20% roughly found by TGA. The same observation can be made in the case of the D-A copolymer P(DTS-DAP) whose TGA is provided in SI. So, this explanation was added in the main text, in lines 353 and 362.

1. The cited references were too old. New references for recent three years should be cited. For example, for DPP in this paper, new references about opto/electronic studies should be cieted, such as Adv. Mater., 2020, 32, 1903882; Org. Chem. Front 2021, 8, 4560; J. Phys. Chem. Lett. 2022, 13, 1131.

These references have been added in ref 23.

1. Diketo-pyrrolo pyrrole means the center unit, but not include the flanked thiophene of it. Since the aromatic group flanked by DPP can be benzene, thiophene, selenophene etc. The author should point out what they used in this paper is thiophene-flanked DPP.

This has been precised in the abstract (line 16) and also in the introduction (line 43).

Author Response File: Author Response.docx

Reviewer 3 Report

In this study Khelifi et al. report the diketo-pyrrolo pyrrole-based acceptor-acceptor (A-A’) copolymers with deep HOMO and LUMO levels absorbing in the near infrared region. Manuscript is written and demonstrated well. Authors should do the following revision before considering for publication.

 

1. Re-check the integration of 1H NMR spectrum of di-bromo BTPBF in Figure S1, If it is the right integration then explain the missing aromatic peaks in the NMR. And also provide the integration of aliphatic protons in the same NMR.
2. It will be great if authors can provide the 13C NMR of di-bromoBTPBF.
3. Provide the reference/s for the statements in line number 58-59 “Besides D-A copolymers, systems combining two electron-accepting A-A’ units have also been reported, affording n-type materials more stable under air, with deeper HOMO levels”.
4. Line number 63 change 0,31% to 0.31%
5. If authors can make a table supporting the improved properties of considered A-A’ over D-A copolymer in one table (in the paper or supplementary information), it will be much visible beneficial for readership.
6. In line number 364 please change the word “poorly” to “limited”.
7. In the Figure 5 change the comma (,) to dot (.) in the entire HOMO and LUMO values.

 

 

 

Author Response

 We sincerely thank you for your review and your comments. Please find below our responses.

1. Re-check the integration of 1H NMR spectrum of di-bromo BTPBF in Figure S1, If it is the right integration then explain the missing aromatic peaks in the NMR. And also provide the integration of aliphatic protons in the same NMR.

The integrations in the 1H NMR spectrum are correct: 0.80 corresponding to 1 proton, both protons of the CH2 close to nitrogen atom appear with an integration of 1.58. These are coherent. There are only 2 aromatic different due to the symmetry in the monomer.

1. It will be great if authors can provide the 13C NMR of di-bromoBTPBF.

The 13C NMR spectrum has been added in the supplementary information, in Figure S1 along with the 1H.

1. Provide the reference/s for the statements in line number 58-59 “Besides D-A copolymers, systems combining two electron-accepting A-A’ units have also been reported, affording n-type materials more stable under air, with deeper HOMO levels”.

In fact the ref [13] was related to that point, so the two first sentences have been modified in the main text for clarification.

1. Line number 63 change 0,31% to 0.31%

This has been corrected.

1. If authors can make a table supporting the improved properties of considered A-A’ over D-A copolymer in one table (in the paper or supplementary information), it will be much visible beneficial for readership.

This was a very good idea. A table has been added at the end of the supplementary information, as a summary of the differences observed between A-A’ and D-A copolymers. The indication of this table has been inserted at the end of the section related to the optoelectronic properties, in line 312.

1. In line number 364 please change the word “poorly” to “limited”.

This has been modified.

1. In the Figure 5 change the comma (,) to dot (.) in the entire HOMO and LUMO values.

This has been corrected.