From Nano-Crystals to Periodically Aggregated Assembly in Arylate Polyesters—Continuous Helicoid or Discrete Cross-Hatch Grating?

Round 1

Reviewer 1 Report

The paper presents the results of research on the morphology of crystals on the surface of a series of homologous arylate polyesters. The analysis of the surface morphology of polymers was carried out on the obtained images using a polarizing microscope, an atomic force microscope, and Scanning Electron Microscope. The molecular weights of the polymers were determined using gel permeation chromatography. The obtained images of the surface of the arylate polyesters have been discussed in detail. In my opinion, the work contains elements of scientific novelty. I consider the mechanisms of packing lamellae into birefringent bands proposed by the authors to be the main achievement. I did not find any errors in the work that need to be corrected. However, before publication, I suggest that the authors should re-analyse the work. The way the work is written does not encourage reading it. An example may be the lack of a clearly defined research goal. For this reason, it would be good to analyse the text before publication and improve the language.

Author Response

Referee #1 Comments and Suggestions for Authors

The paper presents the results of research on the morphology of crystals on the surface of a series of homologous arylate polyesters. The analysis of the surface morphology of polymers was carried out on the obtained images using a polarizing microscope, an atomic force microscope, and Scanning Electron Microscope. The molecular weights of the polymers were determined using gel permeation chromatography. The obtained images of the surface of the arylate polyesters have been discussed in detail. In my opinion, the work contains elements of scientific novelty. I consider the mechanisms of packing lamellae into birefringent bands proposed by the authors to be the main achievement. I did not find any errors in the work that need to be corrected.

However, before publication, I suggest that the authors should re-analyse the work. The way the work is written does not encourage reading it. An example may be the lack of a clearly defined research goal. For this reason, it would be good to analyse the text before publication and improve the language.

Authors’ revisions: We accept the criticism of Referee #1. By following the tip of another referee’s (#3) instruction, we have revised the paragraphs (texts in blue fonts), which we think are more appropriately reflecting the objective of this continuing work. By additional revisions in responding to other Referees’ (#2-#4) comments, we have enhanced the logics and analyses of this manuscript.

Author Response File: Author Response.docx

Reviewer 2 Report

Report on the paper by Yang et al.

Unfortunately, the main results of the present paper are on micro-meter scale, and thus the paper is not suitable for Nanomaterials.

Author Response

Comments by Referee #2

Unfortunately, the main results of the present paper are on micro-meter scale, and thus the paper is not suitable for Nanomaterials.

Authors’ revisions/responses:  We fully respect the referee’s judgement. But we would like to emphasize that the final assembled entities in this work indeed are in scales of micrometers; but the starting crystal-by-crystal packing in in nano-meter scale (single crystals that self-assemble into spherulitic aggregates.). The assembly is in a hierarchical scale-up from nano- to micrometers. We aimed to prove in this work that the assembly is based on discrete cross-hatch grating, whose constituents are mainly nano-meter single crystals. 

We leave it to Editor to decide its suitability in this journal. Should the Editor feel the same way as Referee #2, we will gracefully seek publication elsewhere it more appropriately belongs to.

Author Response File: Author Response.docx

Reviewer 3 Report

In this work, the crystallization mechanism of PDT is studied in detail by microscopy techniques. The manuscript is hard to follow for two reasons: a) It is poorly organized and it is not quite clear what experiments were performed. There are a lot of discussions and results from previous works and thus the text has no coherence, and b) English need improvement. Below there are some other major and minor issues.

Major issues

1.      Lines 151-156. The resolution of microscopes is governed by diffraction effects which occur in sizes comparable to the wavelength of incident light. The number mentioned by the authors for the minimum film thickness (3 μm) is rather close to the resolution of optical microscopes. I think the authors should consult an expert in Optics for this issue in order to make sure that the requirement for minimum film thickness of 3 μm does not arise from diffraction effects.

2.      Since these polymers exhibit polymorphsim, I believe that it is completely inappropriate to discuss crystallization mechanism without mentioning or studying the crystal structure by XRD. Perhaps the monomorphic and polymorphic polymers mentioned in lines 50-54 which may or may not exhibit ring banded pattern have common crystal type?

Minor issues

3.      Explain “PDT” in abstract

4.      Revise last paragraph of introduction

5.      Section 2. Please provide details about the film preparation.

6.      Line 93 was not were

7.      Line 97 English improvement

8.      Line 136 delete the full stop and use comma instead

9.      Line 139. “I” must be small not capital in the word “Interestingly”

10.  Line 173 revise “corresponding”

Author Response

Referee #3 - Comments and Suggestions for Authors

In this work, the crystallization mechanism of PDT is studied in detail by microscopy techniques. The manuscript is hard to follow for two reasons: a) It is poorly organized and it is not quite clear what experiments were performed. There are a lot of discussions and results from previous works and thus the text has no coherence, and b) English need improvement. Below there are some other major and minor issues.

Authors’ revisions:  We have seriously revised and texts and English syntax errors. Thanks for comments that have helped us to improve.  Other point-by-point responses are shown below.

Major issues

1. Lines 151-156. The resolution of microscopes is governed by diffraction effects which occur in sizes comparable to the wavelength of incident light. The number mentioned by the authors for the minimum film thickness (3 μm) is rather close to the resolution of optical microscopes. I think the authors should consult an expert in Optics for this issue in order to make sure that the requirement for minimum film thickness of 3 μm does not arise from diffraction effects.

Authors’ revisions:  We fully agree with referee’s tech. points, which are sound and deserve attention. Optical microscopy usually has resolution of 1 um or so (wavelength ~0.8 um). But pls. let us to emphasize here that the mentioned texts of “the minimum film thickness (3 μm)” [actually ranging from 3-5 um] refers to the work in a cited publication (old ref. #28) dealing with a different subject (extinction bands). In that cited work, not only POM was used but also AFM images were used as the main evidence for the claims, which were re-cited in this work.  Therefore, the claimed results (cited texts) were not based only on the optical microscopy investigation, but further analyzed by AFM evidence in terms of morphology leading to the extinction bands.

Cited Ref. #28 is listed here: [we say old #28, as there may be new refs. to be added in the revisions as requested by other referees.]

28. Yang, C.-E.; Woo, E.M.; Nagarajan, S. Epicycloid extinction-band assembly in Poly(decamethylene terephthalate) confined in thin films and crystallized at high temperatures. Polymer (Guildf). 2021, 212, 123256.
29. Since these polymers exhibit polymorphsim, I believe that it is completely inappropriate to discuss crystallization mechanism without mentioning or studying the crystal structure by XRD. Perhaps the monomorphic and polymorphic polymers mentioned in lines 50-54 which may or may not exhibit ring banded pattern have common crystal type?

Authors’ revisions:  We understand referee #3’s concerns. But the issue of correlation between crystal lattices and polymorphism with crystallization into banded patterns are a complex issue, which was not the aim of this manuscript. Pls. allow us to mention the following examples with conflicting correlations between the polymorphism and banded patterns: Poly(heptamethylene terephthalate) (PHepT) is known to exhibit polymorphism and banded patterns. By contrast, poly(trimethylene terephthalate) (PTT) is known to known to have monomorphism at the Tc range of banded patterns. poly(nonamethylene terephthalate) (PNT) is known to known to have only monomorphism, yet it develops complex banded patterns. By even more dramatic contrast, poly(hexamethylene terephthalate) (PHT) has complex melting, with polymorphism, but PHT never develops banded patterns.

Pls see references listed as a,b,c in following paragraphs. To avoid that we might be criticized as overly self-citing in manuscript, we simply mention these refs, to referee, rather than citing these extra in the revised manuscript.

1. K. C. Yen, E M. Woo, and K. Tashiro, “Microscopic Fourier-Transformed Infrared Characterization on Multiple Types of Spherulites with Polymorphic Crystals in Poly(heptamethylene terephthalate), Macromol. Rapid Co mmun., 31, 1343-1347 (2010).
2. Y. F. Chen and E M. Woo, “Annular Multi-Shelled Spherulites in Interiors of Bulk-Form Poly(nonamethylene terephthalate)”, Macromol Rapid Commun., 30, 1911-1916 (2009).
3. A. K. Ghosh, E. M. Woo, Y. S. Sun, L. T. Lee, and M. C. Wu “Characterization and Analyses on Complex Melting, Polymorphism, and Crystal Phases in Melt-Crystallized Poly(hexamethylene terephthalate)”, Macromolecules, 38, 4780-4790 (2005).

Minor issues

3. Explain “PDT” in abstract

Authors’ revisions:  We have added “poly(decamethylene terephthalate)”. Indeed, it was a careless omission from our side.

4. Revise last paragraph of introduction

Authors’ revisions:  By following the tip of referee’s instruction, we have revised the paragraphs (texts in blue fonts), which we think more appropriately reflect the objective of this continuing work.

5. Section 2. Please provide details about the film preparation.

Authors’ revisions:  It has been remedied, shown in blue-font texts. Thanks.

6. Line 93 was not were

Authors’ revisions:  It has been corrected. Thanks.

7. Line 97 English improvement

Authors’ revisions:  It has been corrected. Thanks.

8. Line 136 delete the full stop and use comma instead

Authors’ revisions:  It has been fixed. Thanks.

9. Line 139. “I” must be small not capital in the word “Interestingly”

Authors’ revisions:  It has been fixed. Thanks for expert error-checking.

10. Line 173 revise “corresponding”

Authors’ revisions: It has been fixed. Thanks. 

We appreciate referee #3’s careful reading to give us opportunity to check out those syntax errors.

Author Response File: Author Response.docx

Reviewer 4 Report

I enjoyed reading this work on twisted polymer spherulites. While the scientific work is good, the introduction misses to embed the research into the wider field of banded spherulites and the past and current literature. I give the authors the opportunity to add other's works in the field in a revision so that I have not to criticize again excessive self-citation (start searching for authors including 'Bernauer' (first observation of phenomenon), then 'Bart Kahr'. The authors may know of more past and current research than I do in this field.

Author Response

Referee #4 - Comments and Suggestions for Authors

I enjoyed reading this work on twisted polymer spherulites. While the scientific work is good, the introduction misses to embed the research into the wider field of banded spherulites and the past and current literature.

I give the authors the opportunity to add other's works in the field in a revision so that I have not to criticize again excessive self-citation (start searching for authors including 'Bernauer' (first observation of phenomenon), then 'Bart Kahr'. The authors may know of more past and current research than I do in this field.

Authors’ revisions: In the original version, we were putting focus on arylate polyesters only in this article; but indeed these other classical backgrounds are critical and can widen the scopes by including what suggested by referee #4. Thanks for tips of referring to the classical work by 'Bernauer' (first observation of phenomenon of crystal deformation, and series of systematic and critical investigations by 'Bart Kahr' et al. We have added a new short paragraph with necessary citations in the revised version. [blue font texts]

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

No further comments.

Reviewer 3 Report

The authors responded adequately to my comments. I suggest acceptance.