Studies on the Synthesis and Application Properties of a Betaine Surfactant with a Benzene Ring Structure
Round 1
Reviewer 1 Report
Comments about the manuscript applsci-2236648entitled "Studies on synthesis and application properties of betaine surfactant with benzene ring structure".
The manuscript treats about the betaine surfactants with the same hydrophobic group but different hydrophilic ones. Their synthesis and properties in reducing the interfacial tension (IFT), their thermal stability, wettability and emulsification properties were described here.
According to the fact that the obtainbed results are very important from the practical poin of view I recommend the manuscript for the publication.
My comments are as follows:
1. The discrepances in the contact angle measurements should be presented.
2. The statistical analysis of the contact angle measurements should be presented.
3. Figure 8 should be corrected and the title of the figure should be carrefullyt chacked(informations a, b, c and d).
Also the contact angle (minimal) at the figure and in the text should be chacked.
4. Because the contact angle depends also on the drop volume please insert the value as well as describe carefully the conditions of the contact angle measurement(temperature chaber) and conditions of the contact angle measurement. Also the evaporation could chave place in so log time of measurement.
5. Table 2. It should be rather emulsion stability in [s].
Author Response
Response Comments:
Comments from the Reviewer #1
1.The discrepances in the contact angle measurements should be presented.
Response: We thank the reviewer sincerely for the valuable advice. We have read this article critically. We have shown contact angle measurement discrepances in the modified figure, and the angle and time were detailed in the caption of the figure (page 12, Figure 8).
- The statistical analysis of the contact angle measurements should be presented.
Response: We have performed error analysis on the contact angle measurements and present statistical analysis in the redrawn diagram (page11, Figure 7).
- Figure 8 should be corrected and the title of the figure should be carrefullyt chacked(informations a, b, c and d).
Response: We have carefully indicated the information represented by each letter in the title of Figure 8 (a, b, c, d and A, B, C, D) (page 12, the title of Figure 8).
We have made the following correction to the Figure 8 heading:
Figure 8. Contact angle images of 0.2 mmol/L DCB and DSB solutions on paraffin surface at different times: (a) 0 min, 75.60°; (b) 2 min, 50.33°; (c) 10 min, 32.78°; (d) 20 min, 28.36° for DCB and (A) 0 min, 95.60°; (B) 2 min, 70.33°; (C) 10 min, 42.78°; (D) 20 min, 35.26° for DSB.
- Because the contact angle depends also on the drop volume please insert the value as well as describe carefully the conditions of the contact angle measurement(temperature chaber) and conditions of the contact angle measurement. Also the evaporation could chave place in so log time of measurement.
Response: We thank the reviewer sincerely for the valuable advice. We added the test droplet volume (5 μL) and experimental temperature condition (confined space and 25 ± 1℃) in manuscript 2.3.Measurements (page 5, lines 6–9). In addition, we added the results of the blank control experiment in 3.4.Wetting Ability, and clarified that droplet evaporation was weak during the experiment, and the influence on the measurement of the contact angle could be negligible (page 11, lines 14–16).
In fact, before the experiment started, we made strict restrictions on air humidity, temperature and other conditions, and used pure water as the control group for the experiment. As shown in the figure, the volume of the liquid hardly changes over time, and the change of the contact angle is very weak, so the influence of water evaporation on the experiment can be ignored.
- Table 2. It should be rather emulsion stability in [s].
Response: We thank the reviewer sincerely for the valuable advice. We have corrected the headings in Table 2 (page 12, the title of Table 2).
We have made the following correction to the Table 2 heading:
Table 2. Emulsification time of DCB and DSB at different concentrations and temperatures.
Author Response File: 
Author Response.docx
Reviewer 2 Report
1. In the Introduction, the authors state that two surfactants were synthesized, and also provide a synthesis procedure and NMR analysis data. I would like to clarify the question: these surfactants were not synthesized and described earlier? If this is a new synthesis, then it is worth focusing the attention of readers on this point, as this significantly increases the novelty and originality of the research. If these compounds have been previously described, then appropriate references should be given.
2. Due to the structure of the reagents used in the synthesis, the sizes of the hydrophilic parts of DCB and DSB are different: in DCB there is one methylene group between the charged parts, in DSB there are three methylene groups and -OH group. In my opinion, this significantly affects the characteristics of the hydrophilic head. But the authors consider the difference in the behavior of surfactants, taking into account only the difference between carboxy and sulfo groups. Has there been any research done to ignore the difference in hydrophilic head size? How do the authors think this difference might affect the results of their research?
3. It is necessary to clarify the dimension of Y-axis in fig. 1 (TGA) and give the actual percent of weight loss.
4. Throughout the text there is no single spelling of "IFTmin" and" IFTequ" (subscript or in-line).
5. The spelling "contact Angle" is found throughout the text. What is the reason for capitalizing Angle?
6. Figures 4, 5, 6, 7 are placed in the text before they are mentioned. In addition, the text and characters in these figures look very small and fuzzy.
7. The term "oil-philic" (p. 10-11) is not generally accepted. The term oleophilic or lipophilic should be used.
8. In fig. 8, the designations A, B, C, D are given twice. The decoding of these designations is not given in the figure caption. In addition, you should specify the real time values corresponding to the moments A, B, C, D.
9. Typos:
- section 2.2.1: (-0.08 MPa/65°C) should be placed after the words "reduced pressure";
- section 2.2.3: extra dot after "40%" in the first line;
- section 2.3.4: many double spaces;
- figure caption fig. 7: capitalized "Paraffin";
- heading of table 2: superfluous capital letters;
- section conclusion: capitalized "Sulfo-" and "Carboxy-"
10. In the References section, there are many incorrect word breaks when wrapping to the next line.
Author Response
Response Comments:
Comments from the Reviewer #2
- In the Introduction, the authors state that two surfactants were synthesized, and also provide a synthesis procedure and NMR analysis data. I would like to clarify the question: these surfactants were not synthesized and described earlier? If this is a new synthesis, then it is worth focusing the attention of readers on this point, as this significantly increases the novelty and originality of the research. If these compounds have been previously described, then appropriate references should be given.
Response: We thank the reviewer sincerely for the valuable advice and we make sure that this is indeed a new synthesis. According to your suggestion, we have added relevant descriptions in the Abstract, Introduction, Materials and Methods, Conclusion and other parts of our manuscript to highlight its novelty and originality (page 1, lines 1; page 2, lines 10; page 2, lines 29; page 13, lines 7).
- Due to the structure of the reagents used in the synthesis, the sizes of the hydrophilic parts of DCB and DSB are different: in DCB there is one methylene group between the charged parts, in DSB there are three methylene groups and -OH group. In my opinion, this significantly affects the characteristics of the hydrophilic head. But the authors consider the difference in the behavior of surfactants, taking into account only the difference between carboxy and sulfo groups. Has there been any research done to ignore the difference in hydrophilic head size? How do the authors think this difference might affect the results of their research?
Response: We thank the reviewer sincerely for the valuable advice about the effect of hydroxyl group on hydrophilicity of surfactant. It turns out that the suggestions you put forward are of great academic significance. Well before 2013, Wang et al. (Wang, Y., Zhang, Y., Liu, X., Wang, J., Wei, L. and Feng, Y. (2014), Effect of a Hydrophilic Head Group on Krafft Temperature, Surface Activities and Rheological Behaviors of Erucyl Amidobetaines. J Surfact Deterg, 17: 295-301.) comparative studied on the effect of the hydrophilic group on Krafft temperature (TK), surface activities and rheo-logical behaviors of erucyl amidobetaines with sulfonate, hydroxyl-sulfonate or carboxylate were examined. Research showed that sulfobetaine introduction of a hydroxyl group in the head part enhanced the hydrophilicity. This can be explained by the formation of hydrogen bonds between hydroxyl groups and H2O molecules. However, compared to the two sulfobetaines, the carboxybetaine had still much better water solubility. Obviously hydroxysulfobetaine is more suitable for high temperature and salt reservoirs than sulfobetaine. Therefore, this paper is based on the research of carboxyl betaine and hydroxysulfobetaine. In addition, in order to make the article more rigorous, we modified the relevant description in the manuscript (“the sulfonic group” was modified to “the hydroxypropyl sulfonic group”, such as page 5, lines 20).
- It is necessary to clarify the dimension of Y-axis in fig. 1 (TGA) and give the actual percent of weight loss.
Response: We thank the reviewer sincerely for the valuable advice. We have clarified the dimension of Y-axis in fig. 1 (TGA) and gave the actual percent of weight loss in new redraw figure (page 5, Figure 1).
- .Throughout the text there is no single spelling of "IFTmin" and" IFTequ" (subscript or in-line).
Response: Thank you so much for your careful check. We feel sorry for the inconvenience brought to the review process. We have added the full spelling of "IFTmin" and "IFTequ"(subscript) to the manuscript (page 6, lines 27; page 8, the title of Table 1).
- The spelling "contact Angle" is found throughout the text. What is the reason for capitalizing Angle?
Response: Thank you so much for your careful check. We feel sorry for the inconvenience brought to the review process. The capitalization Angle is due to a clerical error. We have changed all “contact Angle” into “contact angle” in the manuscript (such as page 5, lines 5).
- Figures 4, 5, 6, 7 are placed in the text before they are mentioned. In addition, the text and characters in these figures look very small and fuzzy.
Response: Thank you so much for your careful check. We feel sorry for the inconvenience brought to the review process. We have adjusted the position of the figures to put them before they are mentioned. In addition, we have changed the format of all the figures to vector images to improve their clarity (page 5–11, Figure 1–7).
- The term "oil-philic" (p. 10-11) is not generally accepted. The term oleophilic or lipophilic should be used.
Response: Thank you so much for your careful check. We feel sorry for the inconvenience brought to the review process. We have changed "oil-philic" (p.10-11) to "oleophilic" (page 11, lines 11).
- In fig. 8, the designations A, B, C, D are given twice. The decoding of these designations is not given in the figure caption. In addition, you should specify the real time values corresponding to the moments A, B, C, D.
Response: Thank you so much for your careful check. We feel sorry for the inconvenience brought to the review process. We have indicated the meanings and specific values (time and angle) of a, b, c, d and A, B, C, D respectively in the caption of Figure 8 (page 12).
We have made the following correction to the Figure 8 heading:
Figure 8. Contact angle images of 0.2 mmol/L DCB and DSB solutions on paraffin surface at different times: (a) 0 min, 75.60°; (b) 2 min, 50.33°; (c) 10 min, 32.78°; (d) 20 min, 28.36° for DCB and (A) 0 min, 95.60°; (B) 2 min, 70.33°; (C) 10 min, 42.78°; (D) 20 min, 35.26° for DSB.
- Typos:
- section 2.2.1: (-0.08 MPa/65°C) should be placed after the words "reduced pressure";
- section 2.2.3: extra dot after "40%" in the first line;
- section 2.3.4: many double spaces;
- figure caption fig. 7: capitalized "Paraffin";
- heading of table 2: superfluous capital letters;
- section conclusion: capitalized "Sulfo-" and "Carboxy-"
Response: Thank you so much for your careful check. We feel sorry for the inconvenience brought to the review process. We have revised these details and carried out a detailed examination of the entire manuscript.
- In the References section, there are many incorrect word breaks when wrapping to the next line.
Response: Thank you so much for your careful check. We feel sorry for the inconvenience brought to the review process. We have revised the details of the references carefully.
Author Response File: Author Response.docx
