Creating Diverse Patterns on Thin Polystyrene Film through Water-in-Oil Emulsion Coating and Utilizing the Derived Hydrophilic Holes as a Microreactor

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. Structurally, one should introduce their main work content after reviewing all the literature, and the last two paragraphs on the second page should be placed at the end of the introduction;

Section 2.1, what is the difference between Flocka Chemical and Flocka Company in the introduction of raw materials? ATO comes from Fluka Chemical, while CTAB comes from Fluka?

3. The format still needs further optimization. For example, the first paragraph of section 2.2 on the fourth page is indented too much; The symbol g for the glass transition temperature on page 12, line 461, should be subscript.

The resonance frequency of the probe described on page 6, line 244 is too high. According to the description of probe size and force constant, the resonance frequency given in the manuscript exceeds the normal value. Please confirm;

5. The thermal analysis curve in Figure 4 should indicate the direction of heat release or absorption;

There is ambiguity in the discussion on the melting peak of PS CTAB composites on page 9. The author should consider that the endothermic peak observed in the composite of CTAB and PS should not be referred to as the melting peak, as there is no crystal disintegration here. It seems reasonable to attribute it to the thawing of a functional group, but even so, other experimental evidence or literature support is needed. Furthermore, it cannot be referred to as first-order phase transition and melting.

The explanation on page 11, lines 406 to 407, regarding the absence of a melting peak seems unreasonable, and whether the melting peak occurs is not directly related to the formation of chemical bonds;

The scale of the transmission electron microscope image in Figure 13 on page 19 should be clearer;

The conclusion section lacks emphasis. The author should extract and identify the conclusions and patterns of the core parts.

10. Supporting documents should be carefully edited. The absorption peak at position 1744-1 in the middle curve of Figure S4 should not be labeled as CO2 but should be represented using the standard labeling method for carbonyl groups.

Comments on the Quality of English Language

English in this paper is good.

Author Response

Reviewer One

1. Structurally, one should introduce their main work content after reviewing all the literature, and the last two paragraphs on the second page should be placed at the end of the introduction.

Response: Thank you for highlighting this point. As mentioned, the last paragraphs (starting with lines 69 and 91, respectively) on page 2 indeed summarize prior research results on the development of surface patterns. The key contributions of this manuscript are found in the final two paragraphs of the Introduction.

2. Section 2.1, what is the difference between Flocka Chemical and Flocka Company in the introduction of raw materials? ATO comes from Fluka Chemical, while CTAB comes from Fluka?

Response: Thank you for pointing out this inconsistency, Fluka is now used for those chemicals obtained from Fluka Chemical Corp.

3. The format still needs further optimization. For example, the first paragraph of section 2.2 on the fourth page is indented too much; The symbol g for the glass transition temperature on page 12, line 461, should be subscript.

Response: Thank you for pointing out this flaw in section 2.2. The only paragraph in this section has been divided into three paragraphs, and any overly elaborate parts have been trimmed. The use of the symbol T_g has been standardized.

4. The resonance frequency of the probe described on page 6, line 244 is too high. According to the description of probe size and force constant, the resonance frequency given in the manuscript exceeds the normal value. Please confirm.

Response: Thank you for checking this AFM scanning condition. The first author’s experimental records show this exact frequency. Additionally, the AFM unit, Digital Instruments Nanoscope IIIa, offers a resonant frequency for tapping mode in air cantilevers between 50 to 400 kHz.

5. The thermal analysis curve in Figure 4 should indicate the direction of heat release or absorption;

Response: Thank you for pointing out this defect, the DSC heat flow direction in Figure 4 has been specified. 

6. There is ambiguity in the discussion on the melting peak of PS CTAB composites on page 9. The author should consider that the endothermic peak observed in the composite of CTAB and PS should not be referred to as the melting peak, as there is no crystal disintegration here. It seems reasonable to attribute it to the thawing of a functional group, but even so, other experimental evidence or literature support is needed. Furthermore, it cannot be referred to as first-order phase transition and melting.

Response:

 

Thank you for this valuable comment. Although the discussion pertaining the endothermic peak does not attribute it to the melting of CTAB but to the thawing of the array of quaternary cations, it is inappropriate to describe the peak as a first-order phase transition.  In this revision, as suggested, a publication [37] has been cited (in line 387) to support the notion that once CTAB is incorporated into PS via the emulsion method, it does not form a spatially uniform composite with PS. This publication also found that the endothermic behavior of CTAB covering the surface of PS latex particles exhibits a melting peak at the same temperature as shown in Figure 4.

 

7. The explanation on page 11, lines 406 to 407, regarding the absence of a melting peak seems unreasonable, and whether the melting peak occurs is not directly related to the formation of chemical bonds.

Response: Thank you for this insightful query. Compared to CTAB, AOT has completely different characteristics, resulting in a different scenario regarding its association with PS chains and its surface-enriching state. A few lines of elaboration have been included in the last paragraph under section 3.1.2, along with a related study to support this notion.

8. The scale of the transmission electron microscope image in Figure 13 on page 19 should be clearer;

Response: The Figure has been improved, thank you.

9. The conclusion section lacks emphasis. The author should extract and identify the conclusions and patterns of the core parts.

Response: Thank you for this inspiring point, the conclusion section has been modified to embody the meaning of this study from the fundamental aspect.  

10. Supporting documents should be carefully edited. The absorption peak at position 1744-1 in the middle curve of Figure S4 should not be labeled as CO2 but should be represented using the standard labeling method for carbonyl groups.

Response: Thanks, the corresponding correction has been made.

Reviewer 2 Report

Comments and Suggestions for Authors

This study explored the interest of patterning the surface of a thin polymer film through spin-coating a w/o emulsion on a glass slide, followed by ambient and vacuum drying the emulsion coating layer.

The paper is of great interest in the domain of thin film by w/o emulsion. However, the paper needs some improvements before its acceptance. Indeed, the polymer needs to be more characterized. The surface physicochemical properties of PS have to be determined, more particularly the London dispersive energy and the Lewis acid-base.

On the other hand, it is suitable to determine the contact angle of the deposited film on the glass slide.

The authors are invited to compare their results to similar results in the literature.

Author Response

1. This study explored the interest of patterning the surface of a thin polymer film through spin-coating a w/o emulsion on a glass slide, followed by ambient and vacuum drying the emulsion coating layer. The paper is of great interest in the domain of thin film by w/o emulsion. However, the paper needs some improvements before its acceptance. Indeed, the polymer needs to be more characterized. The surface physicochemical properties of PS have to be determined, more particularly the London dispersive energy and the Lewis acid-base.

Response: Thank you for examining our work from the perspective of fundamental molecular interaction forces. We believe that determining the London dispersion force between PS and a surfactant, for example, would require a comprehensive experimental design, which is beyond the scope of this work.

2. On the other hand, it is suitable to determine the contact angle of the deposited film on the glass slide.

   Response: Thank you for requesting this additional experimental examination. We fully agree that WCA measurement of the patterned surfaces will provide insight into the influence of surface morphology from another perspective. However, we believe that this examination warrants a separate manuscript.

3. The authors are invited to compare their results to similar results in the literature.

Response: In this revision, we have carefully addressed this aspect by adding references 12, 18, 37, and 39, along with related elaborations, to support the need for this research.

Reviewer 3 Report

Comments and Suggestions for Authors

The reviewed article is devoted to the effect of the formation of various patterns on a smooth glass surface on which a drop of emulsion containing a polystyrene solution is applied. Due to non-uniform drying, a self-organized structure is formed on the surface.

It should immediately be noted that this method of formation of a self-organized structure (“Mesoscopic Patterning”) due to drying of the liquid phase was first proposed and described in detail in the work of E. Bormashenko et al., Macromol. Chem. and Phys. v. 208, pp 567-576 (2008). Also some other articles om this ytopic were published by this group. I believe that it is necessary to mention this publication as a pioneering study.

At the same time, it should be agreed that the authors do not repeat the earlier work, but essentially expand the research methodology and add significantly new experimental results, which demonstrate not only the formation of different patterns, but also show its functional significance as centers of crystallization of various organic and inorganic substances. The study was carried out very accurately, and the description of experimental protocols and the results obtained were made on the high level. Structural characterization ewer fulfilled also quite satisfactory. In this regard, the work under review is certainly original and contains new interesting results that deserve publication.

The following comments should be considered by the authors.

1.     Necessity of more accurate citing and an indication of priority is evident.

2.     А description of all the results obtained is presented in qualitative form as  different images (pictures). They are quite interesting and cleasr. However, I would very much wait for a quantitative analysis of the distribution of “holes” on surface and their size. There is clearly a lack of quantitative assessment of the regularity of the structure and other quantitative estimations.

3.     Maybe, it would be useful to follow the kinetics of crystallization (if possible) dependent on the structure pattern.

4.     Up to me, the Conclusion section is not satisfactory, since really, it shortly repeat the content and quantitative results of the study/ It is expected that Conclusion should formulate scientific results generalizing the physical effects observed and their reasons but not experimental observations by themselves.  

Author Response

 

1. The reviewed article is devoted to the effect of the formation of various patterns on a smooth glass surface on which a drop of emulsion containing a polystyrene solution is applied. Due to non-uniform drying, a self-organized structure is formed on the surface.

 

Response: Thank you for this comment emphasizing the notion of non-uniform drying of the w/o emulsion coating. The concept has been incorporated in line 342.

 

 

2. It should immediately be noted that this method of formation of a self-organized structure (“Mesoscopic Patterning”) due to drying of the liquid phase was first proposed and described in detail in the work of E. Bormashenko et al.,  Chem. and Phys.v. 208, pp 567-576 (2008). Also some other articles om this ytopic were published by this group. I believe that it is necessary to mention this publication as a pioneering study.

 

Response: Thank you for pointing this missing of citation. In this revision, the prior art referenced as ref. 12 has been cited and acknowledged in lines 65-68.

 

 

3. At the same time, it should be agreed that the authors do not repeat the earlier work, but essentially expand the research methodology and add significantly new experimental results, which demonstrate not only the formation of different patterns, but also show its functional significance as centers of crystallization of various organic and inorganic substances. The study was carried out very accurately, and the description of experimental protocols and the results obtained were made on the high level. Structural characterization ewer fulfilled also quite satisfactory. In this regard, the work under review is certainly original and contains new interesting results that deserve publication.

 

Response: Thank you for this positive comment.

 

 

4. The following comments should be considered by the authors. Necessity of more accurate citing and an indication of priorityis evident.

Response: Indeed, besides including reference 12 mentioned above, the current amendment also updated one of the references for the dewetting technique (ref. 15) and included ref. 18 for a modified breath-figure approach.

 

5. Аdescription of all the results obtained is presented in qualitative form as different images (pictures). They are quite interesting and cleasr. However, I would very much wait for a quantitative analysis of the distribution of “holes” on surface and their size. There is clearly a lack of quantitative assessment of the regularity of the structure and other quantitative estimations.

 

Response: Thanks for this valuable comment. In this study the two films, PS_CTAB_0.67 and PS_Span-80_0.67, display the most closely packed surface holes. Based on their respective SEM images (Figures 2a and 7d), the statistical data are provided in line 317 on page 8 and in line 553 on page 14. 

 

6. Maybe, it would be useful to follow the kinetics of crystallization (if possible) dependent on the structure pattern.

 

Response: Thank you for this inspiring comment. We did not monitor the real-time crystallization of AM on PS_Span-80_0.67 film by XRD, but this examination deserves further pursuit to understand the impact of the microenvironment.

 

7. Up to me, the Conclusion section is not satisfactory, since really, it shortly repeat the content and quantitative results of the study/ It is expected that Conclusion should formulate scientific results generalizing the physical effects observed and their reasons but not experimental observations by themselves.  

Response: Thank you for pointing out this weak aspect. In this revision, we have tried to enhance the conclusion by focusing on fundamental insights.

Reviewer 4 Report

Comments and Suggestions for Authors

The paper from Hauan and Hong studies the surface morphology of PS thin films (obtained through solution casting), as a consequence of the incorporation of a little amount of water into the chloroform-PS solution containing a dissolved emulsifier. In addition, bowl-shaped holes that form on PS surface during the evaporation of the solvent can be exploited as microreactors to carry out the crystallization of acrylamide, the growth of Ni-P alloy dendrites by electroless plating, or the in-situ reduction and formation of copper nanoparticles.

The manuscript shows some novelty and originality and the conclusions are quite well supported by the experimental data. Besides, references are balanced and appropriately cited.

Some comments and suggestions are listed as follows:

- Figure 4: please add the scale on Y axis. The caption on Y axis (DSC mW/mg) should be replaced with "Heat flow mW/mg". Besides, the DSC trace referring to PS sample shows a relaxation enthalpy phenomenon: therefore, instead of performing 1 heating up only, the sample should be subjected to (i) firt heating up at 10°C/min, (ii) cooling down (at -10°C/min) and (iii) second heating up at 10°C/min. The Tg should be measured on the 2nd heating up. The same suggestion can be proposed also for Figure 6, Figure 8, and Figure 9.

- Figure 4: the DSC trace referring to PS_CTAB_0.67 does not show any Tg step: the statements provided in lines 349-352 should be omitted.

- Figure 7 (d): please use the same magnification of the other three images

Author Response

Some comments and suggestions are listed as follows:

1. Figure 4: please add the scale on Y axis. The caption on Y axis (DSC mW/mg) should be replaced with "Heat flow mW/mg".

Response: We have made the change, thank you.

 

2. Besides, the DSC trace referring to PS sample shows a relaxation enthalpy phenomenon: therefore, instead of performing 1 heating up only, the sample should be subjected to (i) firt heating up at 10°C/min, (ii) cooling down (at -10°C/min) and (iii) second heating up at 10°C/min. The Tg should be measured on the 2nd heating up. The same suggestion can be proposed also for Figure 6, Figure 8, and Figure 9.

 

Response: Yes, we erased any thermal history of each sample through the first scan and recorded the thermal responses of the samples using the subsequent scan. In the revised version, we added this pretreatment step in section 2.6.3.

 

3. Figure 4: the DSC trace referring to PS_CTAB_0.67 does not show any Tg step: the statements provided in lines 349-352 should be omitted.

Response: Thank you for pointing out this mistake. The related elaboration has been amended (in lines 377-378.

 

4. Figure 7 (d): please use the same magnification of the other three images

Response: The SEM image of this sample was collected at only 4k magnification, so we have retained it in the revised version. Thank you for mentioning this issue.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors did not give a satisfactory response.

1. In the first comment I invited the authors to give information on the London dispersive surface energy and Lewis's acid-base properties of PS. If the authors have no time to determine these surface properties. At least, they can find this information in the literature.

2. I insist on determining the contact angle of the deposited film on the glass slide. this parameter is essential to be known in this study. However, the full determination of the contact angle by varying the different surface parameters can be carried out in the future. But here some experiments on the contact angle of the 2D films do not take a long time to be performed.

  

Author Response

Comment 1.

The authors did not give a satisfactory response. In the first comment I invited the authors to give information on the London dispersive surface energy and Lewis's acid-base properties of PS. If the authors have no time to determine these surface properties. At least, they can find this information in the literature.

 

Response:

Thanks for your valuable comment helping enhance the fundamental insight of this paper. In response, we have added a section (3.1.4 starting from line 575) that evaluates the London dispersion forces between PS and the hydrophobic tails of the surfactants studied. This new section compares the Hansen solubility parameter of each surfactant’s tail with that of PS, because both are non-polar and thus associate primarily by the dispersion forces. Additionally, we have included five new references (40 to 44) to support the flow and content of this section.

 

Comment 2.

 I insist on determining the contact angle of the deposited film on the glass slide. this parameter is essential to be known in this study. However, the full determination of the contact angle by varying the different surface parameters can be carried out in the future. But here some experiments on the contact angle of the 2D films do not take a long time to be performed.

Response:

Thank you for this essential comment. We completely agree that measuring the water contact angle and its hysteresis is crucial for fully characterizing the surface patterns achieved. However, since this project was concluded several years ago, carrying out contact angle measurements from sample preparation within a short timeframe is unlikely.

In response, we have included a qualitative analysis in the last paragraph of the newly added section, as mentioned earlier. This analysis discusses the general trends in how surface hydrophilicity and morphology affect water contact measurements and their hysteresis values. We hope these preliminary insights address your requirements.

Reviewer 3 Report

Comments and Suggestions for Authors

I recommend the manuscript for publication as it is

Author Response

Thank you for your recommendation.

Reviewer 4 Report

Comments and Suggestions for Authors

The revised manuscript is suitable for publication

Author Response

Thank you for your recommendation.