Reversibility of Swelling, pH Sensitivity, Electroconductivity, and Mechanical Properties of Composites Based on Polyacrylic Acid Hydrogels and Conducting Polymers
Round 1
Reviewer 1 Report
In this manuscript, the composites based on polyacrylic acid gels as matrices and conducting polymers (polyaniline, polypyrrole) as functional components have been obtained. It was observed that the new composites are characterized by the combination of swelling capacity, pH-sensitivity and electroconductivity. However, there are some unclear descriptions that make it somewhat doubtful. The authors should address several following major issues.
1. The introductory logic is unreasonable. the author may consider the logical sequence: first introduce polyacrylic electrolyte hydrogel, electric field activation, and then introduce conductive polymer from low conductivity.
2. As described in line 173, validation of PAA matrix infrared spectroscopy should be added.
3. Described in lines 184-187, draw a table comparing the second swelling.
4. Described in lines 280-289, draw a table comparing the second cycle of swelling/contraction.
5. Please additional experiments to verify the reversibility of the swelling/contraction process of PAA-PPy and PAA-PANI.
6. Relevant literature needs to be referenced and cited. 10.1002/adfm.202011073; 10.1039/d2ta03559f; 10.1002/advs.202300650
Moderate editing of English language required.
Author Response
In this manuscript, the composites based on polyacrylic acid gels as matrices and conducting polymers (polyaniline, polypyrrole) as functional components have been obtained. It was observed that the new composites are characterized by the combination of swelling capacity, pH-sensitivity and electroconductivity. However, there are some unclear descriptions that make it somewhat doubtful. The authors should address several following major issues.Thank you very much for the remarks. Please, find our responses.
- The introductory logic is unreasonable. the author may consider the logical sequence: first introduce polyacrylic electrolyte hydrogel, electric field activation, and then introduce conductive polymer from low conductivity.
Response: The Introduction is corrected.
- As described in line 173, validation of PAA matrix infrared spectroscopy should be added.
Response: IR spectroscopy (Figure 3) is added.
- Described in lines 184-187, draw a table comparing the second swelling.
Response: It is made (Table 2).
- Described in lines 280-289, draw a table comparing the second cycle of swelling/contraction.
Response: It is made.
- Please additional experiments to verify the reversibility of the swelling/contraction process of PAA-PPy and PAA-PANI.
Response:
The evidence of irreversibility is the facts that the mass of gel after the cycle swelling/contraction differs from the initial mass of this sample and also there is a change of its swelling degree at the second cycle as compared with one at the first cycle. It means that the sample did not recover in the initial state after the first cycle because of changes in the composition or structure of the gel. These evidences are presented in the paper.
- Relevant literature needs to be referenced and cited. 10.1002/adfm.202011073; 10.1039/d2ta03559f; 10.1002/advs.202300650:
The mechanism of a PVDF/CsPbBr3 perovskite composite fiber as a self-polarization piezoelectric nanogenerator with ultra-high output voltage.
Heterojunction Engineering Enhanced Self-Polarization of PVDF/CsPbBr3/Ti3C2Tx Composite Fiber for Ultra-High Voltage Piezoelectric Nanogenerator.
Response: The references are cited [Refs. 12-14]
Reviewer 2 Report
The manuscript reports the reversibility of swelling, pH sensitivity, conductivity and mechanical properties of polyacrylic acid hydrogels and conductive polymer composites. The manuscript needs a major revision before publication in Journal of Composites Science.
Comments:
1) In Figure 1, when AA concentration increases (PAA-20 and PAA-25), the volume of PAA hydrogel expands into cylindrical blocks is not obvious, so it is suggested to give a more obvious comparison figure.
2) Table 2 suggests a detailed test curve of the mechanical properties of PAA hydrogel expansion in pH = 6.4 water.
3) How to get that the mass content of conductive components in PAA/PPy composites given in Table 3 is lower than that of PAA/PANI composites?
4) It is suggested to add physical pictures in Table 4 to express the expansion data of PAA matrix and composite materials PAA/PANI and PAA/PPy.
5) It is suggested that detailed mechanical property test diagrams should be given in Tables 2, 7 and 6.
6) This paper discusses AA concentrations of 15, 20 and 25%. Is it possible to study a range of concentrations?
7) Please refer to the reference, to discuss the mechanical properties of the composite hydrogels: J. Mater. Sci. 2020, 55(29), 14690-14701, Doi: 10.1007/s10853-020-05063-x. The reference should be also cited in the revision.
Author Response
Thank you very much for the remarks. Please, find our responses.
- In Figure 1, when AA concentration increases (PAA-20 and PAA-25), the volume of PAA hydrogel expands into cylindrical blocks is not obvious, so it is suggested to give a more obvious comparison figure.
Response: Figure 1 is corrected.
2) Table 2 suggests a detailed test curve of the mechanical properties of PAA hydrogel expansion in pH = 6.4 water.
Response: The curves of the mechanical properties of PAA hydrogel expansion in pH = 6.4 water
are added (Figure 5).
3) How to get that the mass content of conductive components in PAA/PPy composites given in Table 3 is lower than that of PAA/PANI composites?
Response:
The content of components in gel matrix is determined by a number of factors such as the nature of component, its interaction with matrix, rate of polymerization of monomer in these conditions and others. Monomers aniline and pyrrole are different in chemical structure, mobility, intermolecular interactions. It is possible to suppose that aniline monomer penetrates in the gel matrix faster and deeper than monomer of pyrrole, and as a result the thicker layer of PANI is formed in the matrix. Note that the higher rate of PANI layer formation is confirmed by its looser and less clearly defined structure (Fig. 7b). It is clear that the layer of the formed rigid-chain conducting polymers will prevent further penetration of the monomers and initiator into the gel to increase the content of the component.
4) It is suggested to add physical pictures in Table 4 to express the expansion data of PAA matrix and composite materials PAA/PANI and PAA/PPy.
Response: Unfortunately, the time for correcting the article does not allow preparing samples for pictures. This process takes at least 2 - 3 weeks.
5) It is suggested that detailed mechanical property test diagrams should be given in Tables 2, 7 and 6.
Response: The mechanical property test diagrams to the Tables 3, 7 and 8 are given (Figures 5, 9).
6) This paper discusses AA concentrations of 15, 20 and 25%. Is it possible to study a range of concentrations?
Response:
It could be possible to study AA other concentrations but our research has shown that a too large swelling of the gels prepared at the lower than 15% concentrations leads to rupture of the gel network. At the same time, the gels prepared at the higher than 25% concentrations show too little swelling and weak influence of parameters for investigations.
7) Please refer to the reference, to discuss the mechanical properties of the composite hydrogels: J. Mater. Sci. 2020, 55(29), 14690-14701, Doi: 10.1007/s10853-020-05063-x. The reference should be also cited in the revision.
Journal of Materials Science & Technology. Volume 52, 1 September 2020, Pages 29-62. Recent progresses on designing and manufacturing of bulk refractory alloys with high performances based on controlling interfaces (металлы). T. Zhang a, H.W. Deng b, Z.M. Xie b, R. Liu b, J.F. Yang b, C.S. Liu b, X.P. Wang b, Q.F. Fang b, Y. Xiong c. https://doi.org/10.1016/j.jmst.2020.02.046
Journal of Materials Science volume 55, pages14690–14701 (2020). Mechanical enhancement of graphene oxide-filled chitosan-based composite hydrogels by multiple mechanisms. Yiwan Huang, Longya Xiao, Ju Zhou, Xuefeng Li, Jianxin Liu, Ming Zeng. Doi: 10.1007/s10853-020-05063-x
Response: The references are cited in the revision [Refs. 10-11].
Reviewer 3 Report
The authors describe the synthesis of composites using polyacrylic acid gels as matrices and conducting polymers (polyaniline, polypyrrole) as functional components.
1. The introduction follows the same format as the article: “Electroactive hydrogels based on poly(acrylic acid) and polypyrrole, ISSN 0965545X, Polymer Science, Ser. A, 2011, Vol. 53, No. 1, pp. 67–74. © Pleiades Publishing, Ltd., 2011”, and the first four references are identical and do not date from recent years.
2. The bibliography needs to be updated; the most recent year listed is 2017.
3. Please indicate which are differences between this recent article and you previous works: 1. “Electroactive hydrogels based on poly(acrylic acid) and polypyrrole, ISSN 0965545X, Polymer Science, Ser. A, 2011, Vol. 53, No. 1, pp. 67–74. © Pleiades Publishing, Ltd., 2011”; and 2. “Bel’nikevich, N.G.; Bobrova, N.V.; Elokhovskii, V.Yu.; Zoolshoev, Z.F.; Smirnov, M.A.; Elyashevich G.K. Effect of initiator on 393 the structure of hydrogels of cross-linked polyacrylic acid. Russian Journal of Applied Chemistry 2011, 84, 2106-2113”?
4. What makes this work unique in the field in comparison to your previous works?
5. You prepared cross-linked polyacrylic acid (PAA) in the same concentrations of AA 15, 20, and 25% (PAA-15, PAA-20, and PAA-25) as described in the preceding article “Electroactive hydrogels based on poly(acrylic acid) and polypyrrole, ISSN 0965545X, Polymer Science, Ser. A, 2011, Vol. 53, No. 1, pp. 67–74. © Pleiades Publishing, Ltd., 2011”, and using the same initiator, as you described in “Bel’nikevich, N.G.; Bobrova, N.V.; Elokhovskii, V.Yu.; Zoolshoev, Z.F.; Smirnov, M.A.; Elyashevich G.K. Effect of initiator on 393 the structure of hydrogels of cross-linked polyacrylic acid. Russian Journal of Applied Chemistry 2011, 84, 2106-2113”, please comment.
6. Degree of crosslinking for PAA-15 and PAA-25 is already studied in your previous work (doi:10.1134/s1070427211120160). In this work it was concluded that “The “ideal” network is formed at a monomer concentration of 10–15% with both initiators”. So, why did you re-optimize the hydrogel composition in section 3.1 and then develop composites containing 15%, 20%, 25% AA? Please comment.
7. In Fig. 4, this scheme confirms that the composite was obtained using the same method as in your previous work (doi:10.1134/s0965545x11010068). Please specify the novelty.
8. The estimation accuracy of the parameters from Tables 1 to 7 (what is the approximation accuracy) should be given.
9. How did the authors arrive at particle sizes of approximately 150-300 nm in PAA/PANI and 40-50 nm in PAA/PPy?
10. The conclusions are not representative. Please compare your results.
Author Response
Thank you very much for the remarks. Please, find our responses.
- The introduction follows the same format as the article: “Electroactive hydrogels based on poly(acrylic acid) and polypyrrole, ISSN 0965545X, Polymer Science, Ser. A, 2011, Vol. 53, No. 1, pp. 67–74. © Pleiades Publishing, Ltd., 2011”, and the first four references are identical and do not date from recent years.
Response: The Introduction is corrected.
- The bibliography needs to be updated; the most recent year listed is 2017.
Response: The list of References is corrected.
- Please indicate which are differences between this recent article and you previous works: 1. “Electroactive hydrogels based on poly(acrylic acid) and polypyrrole, ISSN 0965545X, Polymer Science, Ser. A, 2011, Vol. 53, No. 1, pp. 67–74. © Pleiades Publishing, Ltd., 2011”; and 2. “Bel’nikevich, N.G.; Bobrova, N.V.; Elokhovskii, V.Yu.; Zoolshoev, Z.F.; Smirnov, M.A.; Elyashevich G.K. Effect of initiator on 393 the structure of hydrogels of cross-linked polyacrylic acid. Russian Journal of Applied Chemistry 2011, 84, 2106-2113”? (see below)
- What makes this work unique in the field in comparison to your previous works? (see below)
- You prepared cross-linked polyacrylic acid (PAA) in the same concentrations of AA 15, 20, and 25% (PAA-15, PAA-20, and PAA-25) as described in the preceding article “Electroactive hydrogels based on poly(acrylic acid) and polypyrrole, ISSN 0965545X, Polymer Science, Ser. A, 2011, Vol. 53, No. 1, pp. 67–74. © Pleiades Publishing, Ltd., 2011”, and using the same initiator, as you described in “Bel’nikevich, N.G.; Bobrova, N.V.; Elokhovskii, V.Yu.; Zoolshoev, Z.F.; Smirnov, M.A.; Elyashevich G.K. Effect of initiator on 393 the structure of hydrogels of cross-linked polyacrylic acid. Russian Journal of Applied Chemistry 2011, 84, 2106-2113”, please comment. (see below)
The response to Remarks 3-5:
In our paper we investigate the dependence of swelling degree on crosslinking degree in a wide range of pH, and we obtained complete dependence in the entire range of concentrations where the gels are pH-sensitive. It is seen that in the mentioned article only the part of the curve is obtained. For all gels, we have obtained the classic-shaped curves Q (pH) which can be described analytically as result of two different processes. Such curves have not been presented in any publications.
We investigated the reversibility of swelling/contraction (two cycles) for the matrices and the composites – these investigations were not performed in the referenced and other papers.
In the paper (Polymer Science) only PPy was used as component for two PAA matrices (PAA-15, PAA-25). We used three matrices of PAA to obtain the dependences of characteristics for PAA matrices and two types of composites (PAA/PANI and PAA/PPy on these matrices) on pH media and to compare their behavior in swelling/contraction processes and also the mechanical properties. The measurements were performed for all samples. The preparation of this set of sampIes made it possible to investigate and analyze their reversibility of swelling, pH-sensitivity and deformational characteristics, and also to determine the effect of crosslinking degree on the functional properties of the matrices and composites. The results are presented by a large data set in our article. These properties are the very important information for the practical applications using multiple swelling/drying processes.
Thank you for the remarks. We suppose that we have not clearly stated the novelty and significance of our results in the Conclusion.
- Degree of crosslinking for PAA-15 and PAA-25 is already studied in your previous work (doi:10.1134/s1070427211120160). In this work it was concluded that “The “ideal” network is formed at a monomer concentration of 10–15% with both initiators”. So, why did you re-optimize the hydrogel composition in section 3.1 and then develop composites containing 15%, 20%, 25% AA? Please comment.
Response:
The term “ideal” (in quotation marks) network in the referenced article, it was only meant that degree of crosslinking calculated from the swelling is equal to this value, determined by the monomer-crosslinker ratio. It did not mean that some gels are characterized by the better or optimal characteristics and properties as compared with other ones. Therefore, there is no question of optimization.
It is clear that at the low concentrations there are some defects as “tails” of the chains, and at higher concentration the “weaving” of the chains may be formed. In result of the difference in the number of monomers between the crosslinks, the more or less strong dependences of Q on pH for various concentrations are observed though the character of these dependences is the same. It means that these dependences describe the typical behavior of polymer hydrogels as pH-sensitive materials.
- In Fig. 4, this scheme confirms that the composite was obtained using the same method as in your previous work (doi:10.1134/s0965545x11010068). Please specify the novelty.
Response:
Please, see our response to remark 5: we investigated the objects which were not prepared in the mentioned papers, and also we put another tasks and used the number of experimental approaches which did not consider in these papers.
- The estimation accuracy of the parameters from Tables 1 to 7 (what is the approximation accuracy) should be given.
The accuracy for the Tables 3, 7, 8 is added. For other Tables the accuracy is given in the section Experimental.
- How did the authors arrive at particle sizes of approximately 150-300 nm in PAA/PANI and 40-50 nm in PAA/PPy?
Response: The sized of structure elements are shown in the EM figures.
- The conclusions are not representative. Please compare your results.
Response: Thank you for this remark. We have changed the Conclusion, and we hope for the better.
Round 2
Reviewer 1 Report
Accept！
Reviewer 2 Report
The manuscript can be accepted in its current form.
Reviewer 3 Report
The authors of this study responded to the questions and recommendations and detailed them.
