A Bibliometric Survey on Polyisobutylene Manufacture

Round 1

Reviewer 1 Report

Dear Coleagues,

Congratulations on a very interesting article.
When it comes to the language, in a few cases statements such as "charge walking steps" were less understandable to me. Generally, the article is written in the correct technical language.
From the research point of view, it would be valuable to estimate the scope of publications from other languages (Spanish, French, Portuguese, etc.). In the earlier years, many publications were presented in national languages. A comment in the article would be valuable here.
On my part, I also pay attention to the use of these materials in construction, in metal and glass curtain wall structures, as well as in sealing and insulating materials. The construction industry absorbs these modern materials very quickly.
Apart from general comments, I have no specific comments.
Once again, congratulations on your interesting research work.

Best regards

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments to the author

Report on the manuscript entitled "Bibliometric Survey of Polyisobutylene Manufacture" submitted by José Carlos Pinto and coll.

The authors have provided a well-written and comprehensive article that presents a useful overview of the current state of the art on polyisobutylene manufacturing. This review will be of considerable interest for the researchers acting in this field, therefore, I consider it suitable for publication after some minor revisions.

The structure of the article is quite original, with a first part (introduction) dedicated to an overview of the properties and applications of polyisobutylene along with a brief description of the polymerization techniques/conditions and mechanism for the synthesis of conventional polyisobutylene (C-PIB, incorporating internal double bond in the chain: Polymer-CH=C(CH3)) and highly reactive polyisobutylene (HR-PIB, unsaturation at the terminal chain end: Polymer-CH2-C(CH3)=CH2). The introduction section concludes with a very useful table summarizing the characteristics of PIB grade, their main application and the manufacturer as well as the countries involved in their production.

Then, the authors have wisely chosen to present a bibliographic survey in two sections, one for academic articles and the other for patents.

Each section has been classified as follows: year of publication, distribution of scientific journals, dissemination of work by country and research institution, then by experimental conditions: nature of the catalyst/Lewis acid, nature of the co-catalyst/Lewis base, solvent used for polymerization, reaction temperature, and finally a short paragraph concerning the most cited articles in the field.

In order to gain insight into the operating parameters that influence the structures/properties of the resulting polymers, a third section focused on standard principal component analysis. I am not familiar with this correlation methodology, however, it seems to allow numerical analysis of bibliographic data in an accurate manner; unfortunately, the analysis of the data does not allow to determine the adequate conditions to form either c-PIBs or HR-PIBs, highlighting the important variation of the experimental parameters in the cited papers.

Here are some suggestions to improve the quality of the review:

1) Are there other methods of polymerization of isobutylene such as coordination-insertion or radical polymerization? Could the authors add a sentence on this subject,

2) I would remove bibliometric as a keyword because it is probably too general.

3) Table 1 describes the four main steps in cationic polymerization.I would recommend placing the charges instead of the stars, the elementary steps are not clear with the star,

4) Section 2: Replace the title "Materials and Methods" with "Method used for the literature survey"

5) The title of section 3.1.5.2. should be "Lewis base co-catalyst" instead of Lewis acid catalyst

6) page 14, line 459: phenyl instead of fenyl

7) I would recommend to follow the IUPAC rules and mention "dispersity" and not polydispersity

8) There are minor typographical and grammatical errors, but these should be easily corrected during the editing phase.

At this stage, I recommend publication of this review.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

The paper for review I have received is a remarkable bibliometric study on industrial polyisobutylene production processes from Rio de Janeiro. The review is well written and considers the most critical aspects of manufacturing such an important polymer, and fits well in the scope of this journal. Therefore, I highly support the publication in Processes.

Only some minor comments.

• The authors describe polyisobutylene well, also as a polymer with good physical properties. The chemical resistance against most of the strongly destructive chemicals and solvents has to be also mentioned.
• Also, a short description (only some sentences) about the unique application of various polyisobutylenes (for example, star/arborescent polymers or amphiphilic conetworks) would be advantageous. Groups from the University of Akron, the Hungarian Academy of Sciences, and the Czech Academy of Sciences are working on these novel materials.
• Up to now, there are only two examples of successful radical polymerization of isobutylene. The Michl group produced branched polyisobutylenes in toluene with LiCB₁₁(CH₃)₁₂catalyst (JACS, Macromolecules, 2009-2012), while the Hero/Kali group produced polyisobutylene in water using an azo-initiator (Eur Polym J, 2021). Right now, there is no industrial importance of these methods, but they should be suggested in such a review because of the possible future importance.
• Finally, even the data mining phase was ended in 2020, the paper is going to be published in 2021. The authors should add at least a short paragraph about the most important results since that time border.

I strongly support the publication of this review in Processes as it is, or after some minor revision.

Author Response

Please see the attachment.

Author Response File: Author Response.docx