Electrodeposited Copolymer Films with Tunable Conductivity

Round 1

Reviewer 1 Report

11- As you mentioned it can be used as sensitive material for chemiresistor gas sensors, has any preliminary test has been done?

17 – The conductivity you mentioned is it 2*10⁶  or 2*106 ?

40- As you mentioned a similar strategy is used in the synthesizing process, what is novel in your method?

44- You have chosen DiPy just because it contains spacer in a way to decrease conductivity?

48-52 – Give the CAS no/catalog no for all the chemicals and other substrates used

55 – As you say cooled solution what is the temperature?

Define NaH, DMF, AcOEt, Na₂SO₄, And also include in the materials and methods section.

118 – Any reference when you are defining the oxidation of DiPy?

126 – Is there any reason behind choosing these numbers? Instead as a whole ratio of 90:10, 80:20 and 50:50

169 – Resistance mapping from AFM gives only the surface resistance, in order to study the through plan resistance, which is essential for conducting polymers, it is suggested to use advanced conductivity measurement techniques like Electrochemical Impedance Spectroscopy (EIS). And moreover, surface resistance will not be repeatable, it changes frequently.

And there is no report on the conductivity of the samples

If conductivity results could be added into the paper, it would increase its impact further on tunable conductivity.

Author Response

11- As you mentioned it can be used as sensitive material for chemiresistor gas sensors, has any preliminary test has been done?

We have previously developed gas sensors using as active layer either polypyrrole films (Ammonia gas sensors based on polypyrrole films: Influence of electrodeposition parameters, Sensors and Actuators B (2012)‏ 171,‏ 431-439; Ammonia gas sensor based on electrosynthesized polypyrrole films, Talanta (2009)‏ 78,‏ 199-206) or films obtained from mixtures of pyrrole and sulfonated cobalt phthalocyanine (Elaboration of ammonia gas sensors based on electrodeposited polypyrrole-Cobalt phthalocyanine hybrid films, Talanta (2013)‏ 117,‏ 45-54). We plan to do a full study soon, aiming to develop ammonia gas sensors using the conducting copolymer films prepared from pyrrole and 1,12-di-(1-pyrrolyl)dodecane as active layer. However, to date, we have not yet done preliminary tests and we are unable to produce preliminary results.

17 – The conductivity you mentioned is it 2*10⁶  or 2*106 ?

As noticed by the reviewer, there was an error which has been corrected. The correct number is: 2x10⁵. Indeed the highest measured resistance for a copolymer was 13525 and the lowest one was 0.069 leading to a ratio of 13525/0.069 = 196014 ≈ 2X10⁵.

40- As you mentioned a similar strategy is used in the synthesizing process, what is novel in your method?

In our paper, we cite Cihaner et al. who used two monomers, one of which had a spacer arm, in order to produce a copolymer whose conductivity was tuned by varying comonomer ratio. When we used the word “similarly”, it was to say that we also use two monomers, one of which has a spacer arm. However, we don’t use the same monomers as Cihaner et al. and the characterization techniques and the results obtained are very different from the ones obtained in the cited study.

44- You have chosen DiPy just because it contains spacer in a way to decrease conductivity?

The reviewer is right: we chose DiPy because of its spacer arm. Indeed, if two monomers of similar structure are used, the copolymers will exhibit similar conductivities. For example, Warware et al. prepared copolymers from aniline and nitroaniline and obtained copolymers with a conductivity only ranging from 1.53x10^-6 to 3.46x10^-6 S/cm. On the contrary, with a monomer like pyrrole leading to a very conductive polypyrrole and another like DiPy which breaks the conjugation, we obtained very different conductivities (from 7x10^-2 to 1.35x10⁴ S/cm).

These explanations and this reference have been added to the revised manuscript.

48-52 – Give the CAS no/catalog no for all the chemicals and other substrates used

As suggested by the reviewer, the CAS number of all chemicals have been added as well as the information concerning the other substrates.

55 – As you say cooled solution what is the temperature?

Define NaH, DMF, AcOEt, Na₂SO₄, And also include in the materials and methods section.

As suggested by the reviewer, the temperature has been added to the revised manuscript (5°C) as well as the definition of the acronyms.

118 – Any reference when you are defining the oxidation of DiPy?

As suggested by the reviewer a reference related to this oxidation phenomenon has been added to the manuscript (Ref. 21).

126 – Is there any reason behind choosing these numbers? Instead as a whole ratio of 90:10, 80:20 and 50:50

We wanted to mix 1 DiPy monomer for 10 Pyrrole monomers which therefore represents (1/11) x 100 = 9% of DiPy and 91% of Py. Same thing for the other mixtures.

169 – Resistance mapping from AFM gives only the surface resistance, in order to study the through plan resistance, which is essential for conducting polymers, it is suggested to use advanced conductivity measurement techniques like Electrochemical Impedance Spectroscopy (EIS). And moreover, surface resistance will not be repeatable, it changes frequently. And there is no report on the conductivity of the samples. If conductivity results could be added into the paper, it would increase its impact further on tunable conductivity.

The objective of this study was to measure surface resistance of dry copolymer films since the application we would like to develop in the future concerns the fabrication of gas sensors. However, in such sensors, the gas molecules interact with the surface of the polymer film. That is why we think that resistance measurements by AFM technique is really appropriate (it allows to access to the surface resistance of dry samples). In addition, this method is not frequently used which gives originality to this paper. This technique also allows to make resistance mappings, which makes it possible to check the homogeneous distribution or not of the resistance value over the entire surface. For these reasons, this technique seems to be much more interesting than the EIS technique which is limited as indicated by reviewer 3 (and only applicable in liquid). The other methods, for example Van der Pauw techniques or other four-point probes, are very difficult to apply to electrodeposited films since the substrate, on which the film are deposited, is conductive.

 

Reviewer 2 Report

In this work, the authors report electrodeposited copolymer films with tunable conductivity. They varied the ratio of Py and DiPy monomer to assemble a targeted film. The study is simple and informative. I have minor comments on that.

1. Line 17, a mistake was in writing superscript. Please change it.
2. I suggest writing applications such as biosensing, drug delivery, tissue engineering, energy storage, etc. of conducting polymers to emphasize their works to be more applicable. 10.1021/acsami.6b08901; 10.1038/s41598-019-39457-y; 10.1021/acsami.7b17664
3. What are the mechanical properties of the films? In the introduction part authors stated polypyrroles exhibit poor mechanical properties but did not write about in results and discussion.
4. I confuse about why they use LiClO4 as an electrolyte. This is also an oxidizing agent. In that case, Py or DiPy monomer can be polymerized by the presence of LiClO4. In such a condition, how authors can claim the as-fabricated films is purely electropolymerized?
5. According to Figure 4, the particle size in films appeared as in descending order, Py< Py:DiPy 91:9<Py:DiPy 50:50<Py:DiPy 9:91. But the authors showed the roughness (tale 1) was in the opposite trend. Seems confusing. Please recheck.

6. I also suggest checking the conductivity of the samples by an alternate method to countercheck.

 

Author Response

In this work, the authors report electrodeposited copolymer films with tunable conductivity. They varied the ratio of Py and DiPy monomer to assemble a targeted film. The study is simple and informative. I have minor comments on that. Thank you.

1. Line 17, a mistake was in writing superscript. Please change it.

As noticed by the reviewer, there was an error which has been corrected. The correct number is: 2x10⁵. Indeed the highest measured resistance for a copolymer was 13525 and the lowest one was 0.069 leading to a ratio of 13525/0.069 = 196014 ≈ 2X10⁵.

1. I suggest writing applications such as biosensing, drug delivery, tissue engineering, energy storage, etc. of conducting polymers to emphasize their works to be more applicable. 10.1021/acsami.6b08901; 10.1038/s41598-019-39457-y; 10.1021/acsami.7b17664

As suggested by the reviewer, the following references have been added to show that conducting polymers can be used for various applications:

Energy storage:

[7] Yuan, T.; Ruan, J.F.; Zhang, W.M.; Tan, Z.P.; Yang, J.H.; Ma, Z.F.; Zheng, S.Y. Flexible Overoxidized Polypyrrole Films with Orderly Structure as High-Performance Anodes for Li- and Na-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 51, 35114-35122.

Tissue engineering:

[10] Tiwari, A.P.; Bhattarai, D.P.; Maharjan, B.; Ko, S.W.; Kim, H.Y.; Park, C.H.; Kim, C.S. Polydopamine-based Implantable Multifunctional Nanocarpet for Highly Efficient Photothermalchemo Therapy. Scientific Reports 2019, 9, 2943.

Drug delivery:

[11] Tiwari, A.P.; Hwang, Y.I.; Oh, J.M.; Maharjan, B.; Chun, S.; Kim, B.S.; Joshi, M.K.; Park, C.H.; Kim, C.S. pH/NIR-Responsive Polypyrrole-Functionalized Fibrous Localized Drug-Delivery Platform for Synergistic Cancer Therapy. ACS Appl. Mater. Interfaces 2018, 10, 20256-20270.

Biosensors:

[14] Jain, R.; Jadon, N.; Pawaiya, A. Polypyrrole based next generation electrochemical sensors and biosensors: A review. TRAC 2017, 97, 363-373.

1. What are the mechanical properties of the films? In the introduction part authors stated polypyrroles exhibit poor mechanical properties but did not write about in results and discussion.

Our aim here was not to study the mechanical properties of polypyrrole. We only wanted to inform the readers of the poor mechanical properties of polypyrrole films which have been evidenced in numerous works. Indeed, even Diaz, who was the first to electrodeposit polypyrrole films, was aware of the poor mechanical properties and tried to improve them in an article published in 1983 (Diaz et al., IBM J. Res. Dev. 27 (1983) 342-347).

Since the 1980s, many studies have tried to improve these mechanical properties, which could be done only by deviating from the conventional method of electrochemical deposition of pyrrole and most of the time by adding compounds intended to improve this mechanical strength such as carbon nanotubes which led to some of the most interesting results (see for example: M. Ionita et al., Progress in Organic Coatings, 72 (2011) 647-652 or Che et al., J. Mater. Chem. A, 1 (2013) 4057-4066). In other works, the substrate has been silanized or a diazonium has been used both to enhance the adhesion and mechanical properties of the films.

1. I confuse about why they use LiClO4 as an electrolyte. This is also an oxidizing agent. In that case, Py or DiPy monomer can be polymerized by the presence of LiClO4. In such a condition, how authors can claim the as-fabricated films is purely electropolymerized?

The reviewer is right when he says that LiClO₄ is an oxidizing agent. However, its oxidizing power is really pronounced when there is a significant heating or when a high current is applied during a long time, for example when it is used in a battery, but not during electropolymerization reactions performed in soft conditions [a]. It can also be noticed that LiClO₄ is one of the most frequently used supporting salts to carry out the electropolymerization of polypyrrole. You can see for example the works cited just below [b,c,d,e] which used LiClO4 as supporting salt during pyrrole electropolymerization. In addition, studies, including one of ours, has been dedicated to the influence of the nature of the supporting salt on the electropolymerization of polypyrrole and we have shown that perchlorate anions are among the best anions to electropolymerize pyrrole monomers contrary to larger anions like toluenesulfonate or naphthalenesulfonate [f].

[a] K. Xu, Nonaqueous liquid electrolytes for lithium-based rechargeable batteries, Chem. Rev. 104 (2004) 4303-4417.

[b] S.D. Deshpande, J. Kim, S.R. Yun, New electro-active paper actuator using conducting polypyrrole: actuation behaviour in LiClO4 acetonitrile solution, Synthetic Metals 149 (2005) 53-58.

[c] K. West, M.A. Careem, S. Skaarup, An impedance study of the doping of polypyrrole in LiC1O4/PC, Solid State lonics 60 (1993) 153-159.

[d] F. Trinidad, J. Alonso-Lopez, M. Nebot, Electrochemical behaviour of polypyrrole films as secondary battery electrodes in LiClO4-propylene carbonate? J. Appl. Electrochem. 17 (1987) 215-218.

[e] M. Atobe, H. Tsuji, R. Asami, T. Fuchigami, A Study on Doping–Undoping Properties of Polypyrrole Films Electropolymerized under Ultrasonication, J. Electrochem. Soc. 153 (2005) 1.

[f] T. Patois, B. Lakard, S. Monney, X. Roizard, P. Fievet, Characterization of the surface properties of polypyrrole films: Influence of electrodeposition parameters, Synthetic Metals 161 (2011) 2498-2505.

1. According to Figure 4, the particle size in films appeared as in descending order, Py< Py:DiPy 91:9<Py:DiPy 50:50<Py:DiPy 9:91. But the authors showed the roughness (table 1) was in the opposite trend. Seems confusing. Please recheck.

The images in Figure 4 show that the structures of PPy (a,b) are globular and tall. We even observe the presence of a bulge.

On the contrary, the images obtained for the highest % of DiPy show more extended but less tall structures.

Therefore, Figure 4 is not in opposition to Table 1 because if the structure of the copolymers appear more extended than the structures of PPy films, they are also less tall.

1. I also suggest checking the conductivity of the samples by an alternate method to countercheck.

The objective of this study was to measure surface resistance of dry copolymer films since the application we would like to develop in the future concerns the fabrication of gas sensors. However, in such sensors, the gas molecules interact with the surface of the polymer film. That is why we think that resistance measurements by AFM technique is really appropriate (it allows to access to the surface resistance of dry samples). In addition, this method is not frequently used which gives originality to this paper. This technique also allows to make resistance mappings, which makes it possible to check the homogeneous distribution or not of the resistance value over the entire surface. For these reasons, this technique seems to be much more interesting than the EIS technique which is frequently used to determine resistance of samples but is limited as indicated by reviewer 3 (and only applicable in liquid). The other methods, for example Van der Pauw techniques or other four-point probes, are very difficult to apply to electrodeposited films since the substrate, on which the film are deposited, is conductive.

Reviewer 3 Report

Overall comment: It’s an overall good e-chem communication paper on pyrrole co-deposited polymer film. As a reviewer I feel like more discussion in introduction for why this tunable conductivity work might be useful in real world application is necessary. Also I believe few more things should be added in the paper to make it better. 

I have all my comments below which I believe if fully addressed will sufficiently improve this manuscript to be published in electrochem  

1. Line 17: Is it 2x106 or it should be 2x10⁶ ?

2. Line 29: It has “However, few applications have been reported until now because polypyrroles exhibit poor mechanical properties and are hardly soluble in common solvents.” Please include reference for this statement.

And later, author listed that co-polymerization with other monomers will solve this problem. But author did not explain how that was achieved? Even how co-polymerization with DiPy helped to improve mechanical properties of co-polymer was not discussed. This needs to be addressed with experimental results / citation, as mechanical property of polymer is very important in applications.

3. Line 42: Please indicate the conductivity of Py films and include proper references.

4. This whole paper is about conductivity of co-polymers. What equipment was used to examine conductivity? Its not present in the paper. Please include it.

5. AFM is not widely used as a technique for resistance measurement on CPs. Did author try Impedance spectroscopy (EIS)? EIS is not only a very useful technique for resistance measurement of the film but also, it tells a lot about polymer morphology and its electrochemical interaction. I feel like that important aspect is absent here.

6. Author should add electropolymerization reaction schemes in the paper.

7. Please provide color graphs for CV responses. Its easier to see all subsequent CV run separately.

8. How R values in table 1 are acquired? AFM? R, T and Ra values should have standard deviations with the average value. What is the value of n?

9. Author deposited copolymers both from CV and CA. For AFM and SEM which films were used? Also, how they differ in morphology and in conductivity? 

10. Author concluded that the co-polymer is highly tunable in terms of conductivity, then author must include a relation between concentration or Py:DiPy with the conductivity / resistance. A statistical regression analysis is a required item.

11. This paper lacks references of electrodeposited polymer papers which have been used for many different applications such as lab-on-a chip, chem sensor, battery applications etc. These should go in the introduction. Most importantly author must establish a need for variable conductive co-polymers.

Few examples I found here. Please refer / cite these papers appropriately in introduction

Tunable CPs for battery applications / energy

a. Xiaoteng Jia, Yu Ge, Liang Shao, Caiyun Wang, and Gordon G. Wallace. ACS Sustainable Chemistry & Engineering 2019 7 (17), 14321-14340.
DOI: 10.1021/acssuschemeng.9b02315

b. Chunying Yang, Pengfei Zhang, Amit Nautiyal, Shihua Li, Na Liu, Jialin Yin, Kuilin Deng, and Xinyu Zhang. ACS Applied Materials & Interfaces 2019 11 (4), 4258-4267. DOI: 10.1021/acsami.8b19180

Tunable CPs can be used to tune Redox-MHD controlled microfluidic applications / study. Conductivity tunability will tune the flow properties as well. These two papers used electrodeposited PEDOT.  

c. Foysal Z. Khan, Joshua A. Hutcheson, Courtney J. Hunter, Amy J. Powless, Devin Benson, Ingrid Fritsch, and Timothy J. Muldoon. Analytical Chemistry 2018 90 (13), 7862-7870. DOI: 10.1021/acs.analchem.7b05312

d. Foysal Z. Khan and Ingrid Fritsch 2019 J. Electrochem. Soc. 166 H615.

https://doi.org/10.1149/2.0811913jes

I am sure Author could find more good references where tunable conductive CPs can be used for chem sensor and other applications. Please also include those along with the above four references.

Author Response

Overall comment: It’s an overall good e-chem communication paper on pyrrole co-deposited polymer film. As a reviewer I feel like more discussion in introduction for why this tunable conductivity work might be useful in real world application is necessary. Also I believe few more things should be added in the paper to make it better.

I have all my comments below which I believe if fully addressed will sufficiently improve this manuscript to be published in electrochem.

1. Line 17: Is it 2x106 or it should be 2x10⁶ ?

As noticed by the reviewer, there was an error which has been corrected. The correct number is: 2x10⁵.

2. Line 29: It has “However, few applications have been reported until now because polypyrroles exhibit poor mechanical properties and are hardly soluble in common solvents.” Please include reference for this statement. And later, author listed that co-polymerization with other monomers will solve this problem. But author did not explain how that was achieved? Even how co-polymerization with DiPy helped to improve mechanical properties of co-polymer was not discussed. This needs to be addressed with experimental results / citation, as mechanical property of polymer is very important in applications.

In this work, we didn’t study the mechanical properties of the copolymers formed. So, I think it’s better to remove the sentence “However, few applications have been reported until now because polypyrroles exhibit poor mechanical properties and are hardly soluble in common solvents.” if this sentence gives the impression to the reviewer and other readers that this paper will focus on this point.

3. Line 42: Please indicate the conductivity of Py films and include proper references.

The conductivity of polypyrrole films can vary from 10^-8 to 1.5x10² S/cm, depending on the preparation conditions. To obtain a highly conducting polypyrrole film it is necessary to perform p-doping of the oxidized polymer film using anions as counter-ions. To date the most conducting polypyrrole film has been prepared by Wu et al. who prepared polypyrrole films with a conductivity of 150 S/cm using anionic polyelectrolyte poly(styrene sulfonate) as dopant [20]. This information and this reference have been added to the revised manuscript.

[20] Wu, T.M.; Chang, H.L.; Lin, Y.W. Synthesis and characterization of conductive polypyrrole with improved conductivity and processability. Polym. Int. 2009, 58, 1065-1070.

4. This whole paper is about conductivity of co-polymers. What equipment was used to examine conductivity? It’s not present in the paper. Please include it.

We didn’t measure the conductivity of the copolymers but we measure their resistance using the Resiscope mode of a Nano Observer AFM microscope from CSI. Since it is well-know that the conductivity of a material is inversely proportional to its resistance, the conductivity of the different copolymers can be easily deduced from the resistance measurements.

5. AFM is not widely used as a technique for resistance measurement on CPs. Did author try Impedance spectroscopy (EIS)? EIS is not only a very useful technique for resistance measurement of the film but also, it tells a lot about polymer morphology and its electrochemical interaction. I feel like that important aspect is absent here.

The objective of this study was to measure surface resistance of dry copolymer films since the application we would like to develop in the future concerns the fabrication of gas sensors. However, in such sensors, the gas molecules interact with the surface of the polymer film. That is why we think that resistance measurements by AFM technique is really appropriate (it allows to access to the surface resistance of dry samples). In addition, this method is not frequently used which gives originality to this paper. This technique also allows to make resistance mappings, which makes it possible to check the homogeneous distribution or not of the resistance value over the entire surface. For these reasons, this technique seems to be much more interesting than the EIS technique which is only applicable in a liquid. Concerning the morphology, the SEM and AFM images as well as the profilometric measurements seem to give enough information about the morphological features of the copolymer films.

6. Author should add electropolymerization reaction schemes in the paper.

As suggested by the reviewer, the electropolymerization reaction schemes have been added and described in the text. A reference has also been added referring to the established electropolymerization mechanism.

7. Please provide color graphs for CV responses. Its easier to see all subsequent CV run separately.

As suggested by the reviewer, color graphs have been provided for CV responses.

8. How R values in table 1 are acquired? AFM? R, T and Ra values should have standard deviations with the average value. What is the value of n?

Resistance values are obtained from AFM measurements using Resiscope mode as explained in the Experimental Part. Average resistance value is given by the software based on an average over the whole mapped polymer surface. T and Ra average values were obtained from 5 measurements done at different locations of the films. The uncertainty of each parameter has been added to the manuscript.

9. Author deposited copolymers both from CV and CA. For AFM and SEM which films were used? Also, how they differ in morphology and in conductivity? 

Cyclic voltammograms were used to study the oxidation and reaction processes involved in the electropolymerization reaction and to determine the potential value corresponding to the oxidation of the monomers. A platinum wire, with an area of 0.785 mm², was used as working electrode to perform these experiments. On the contrary, FTO substrates, with an area of 1.5 cm², were used as working electrodes to obtain the copolymer films which were used to achieve SEM, AFM and profilometry experiments. All the copolymer films deposited on FTO were obtained through chronoamperometric experiments since it allows to obtain copolymer films in an oxidized state (this information has been added to the manuscript). The morphology of the copolymer films obtained by CV were not studied as well as their conductivity but the conductivity may be lower for the films prepared by CV since the reduced state of the copolymer films is obtained at the end of the CV.

10. Author concluded that the co-polymer is highly tunable in terms of conductivity, then author must include a relation between concentration or Py:DiPy with the conductivity / resistance. A statistical regression analysis is a required item.

Table 1 which gathers resistance values as a function of the composition of the electrolyte clearly shows that the resistance increases when the proportion of DiPy increases. However, there is no linear relationship between resistance and proportion of DiPy. It is therefore not possible to do a linear regression. From our point of view, these results are sufficient to assume that the resistance is tunable because we can choose what order of magnitude of resistance to give to the film by preparing the electrolyte with the appropriate proportions.

 

11. This paper lacks references of electrodeposited polymer papers which have been used for many different applications such as lab-on-a chip, chem sensor, battery applications etc. These should go in the introduction. Most importantly author must establish a need for variable conductive co-polymers.

Few examples I found here. Please refer / cite these papers appropriately in introduction

Tunable CPs for battery applications / energy:

a. Xiaoteng Jia, Yu Ge, Liang Shao, Caiyun Wang, and Gordon G. Wallace. ACS Sustainable Chemistry & Engineering 2019 7 (17), 14321-14340. DOI: 10.1021/acssuschemeng.9b02315

b. Chunying Yang, Pengfei Zhang, Amit Nautiyal, Shihua Li, Na Liu, Jialin Yin, Kuilin Deng, and Xinyu Zhang. ACS Applied Materials & Interfaces 2019 11 (4), 4258-4267. DOI: 10.1021/acsami.8b19180.

Tunable CPs can be used to tune Redox-MHD controlled microfluidic applications / study. Conductivity tunability will tune the flow properties as well. These two papers used electrodeposited PEDOT.  

c. Foysal Z. Khan, Joshua A. Hutcheson, Courtney J. Hunter, Amy J. wless, Devin Benson, Ingrid Fritsch, and Timothy J. Muldoon. Analytical Chemistry 2018 90 (13), 7862-7870. DOI: 10.1021/acs.analchem.7b05312

d. Foysal Z. Khan and Ingrid Fritsch 2019 J. Electrochem. Soc. 166 H615.

https://doi.org/10.1149/2.0811913jes

I am sure Author could find more good references where tunable conductive CPs can be used for chem sensor and other applications. Please also include those along with the above four references.

We have added the references suggested by the reviewer in order to show that conducting polymers can be used for various applications (Refs. 8, 9, 12, 13). As suggested by the reviewer, we have also added 2 other references where tunable conducting copolymers are prepared from a mixture of poly(3,4-ethylenedioxythiophene) and poly(3-hexylthiophene) [18] and from a mixture of aniline and nitroaniline [19].

[8] Jia, X.T.; Ge, Y.; Shao, L.; Wang, C.; Wallace, G.G. Tunable Conducting Polymers: Toward Sustainable and Versatile Batteries. ACS Sustainable Chem. Eng. 2019, 7, 14321-14340.

[9] Yang, C.Y.; Zhang, P.F.; Nautiyal, A.; Li, S.H.; Liu, N.; Yin, J.L.; Deng, K.L.; Zhang, X.Y. Tunable Three-Dimensional Nanostructured Conductive Polymer Hydrogels for Energy-Storage Applications. ACS Appl. Mater. Interfaces 2019, 11, 4258-4267.

[12] Foysal, Z.K.; Hutcheson, J.A.; Hunter, C.J.; Powless, A.J.; Benson, D.; Fritsch, I.; Muldoon, T.J. Redox-Magnetohydrodynamically Controlled Fluid Flow with Poly(3,4-ethylenedioxythiophene) Coupled to an Epitaxial Light Sheet Confocal Microscope for Image Cytometry Applications. Anal. Chem. 2018, 90, 7862-7870.

[13] Foysal, Z.K.; Fritsch, I. Chip-Scale Electrodeposition and Analysis of Poly(3,4-ethylenedioxythiophene) (PEDOT) Films for Enhanced and Sustained Microfluidics Using DC-Redox-Magnetohydrodynamics. J. Electrochem. Soc. 2019, 166, H615.

[18] Jang, K.S.; Kim, D.O. Synchronous vapor-phase polymerization of poly(3,4-ethylenedioxythiophene) and poly(3-hexylthiophene) copolymer systems for tunable optoelectronic properties. Org. Electron. 2010, 11, 1668-1675.

[19] Waware, U.S.; Hamouda, A.M.S.; Majumdar, D. Synthesis, characterization and physicochemical studies of copolymers of aniline and 3‑nitroaniline. Polymer Bulletin 2020, 77, 4469-4488.

 

Round 2

Reviewer 3 Report

Thanks to authors for responding to most of the concerns. But two things caught my attention that needs to be fixed 

1. Reaction mechanism figure has multiple arrows on the product side. Is that by mistake? Should there be only one arrow? Also, reaction (line 150) is pixelated? is it a pasted figure? can it be written down? 

2. Thanks to author including more references. I saw some inconsistencies in reference writing. Such as in ref 12 and 13, the first author name is flipped. It has last name as the first name. It should be, Khan, F.Z. There may be other inconsistencies. Please fix reference structure appropriate for the journal. I would recommend using Endnote.