Theoretical Study on the Thermal Degradation Process of Nylon 6 and Polyhydroxybutyrate

Round 1

Reviewer 1 Report

In this manuscript, the authors address the mechanism of an interesting reaction, the thermal degradation process of Nylon 6 and Polyhydroxybutyrate. They carried out several reactions providing a reasonable scope for future application and computational investigation. The latter was carried out by only KS DFT calculations.

Based on the comments below, my recommendation is that the paper cannot be published in the present form since more computational details must be added to investigate a reaction mechanism.

General comments

1- Since the barrier differences amount to a few kcal/mol, other effects should be included in the computational methodology. The effect of BSSE has not been considered. Please include corrections in the calculations or clearly state limitations.

2- Only free energy DG and DE are shown and discussed. No enthalpy DH barriers are shown despite they have been calculated along with the harmonic analysis.

3- When reporting on calculations, it is recommended that the optimized molecular structures are discussed, their energetics, and finally data are discussed and conclusions are drawn.

4- Many sentences are cited without references. The authors must add all cited pieces of information

5- English needs improvement. Please work through the text carefully from this perspective.

Introduction Section

6- The authors should move the paragraph " Polymer degradation is...." after the first paragraph in this section.

7- The novelty of the present work concerning other state-of-art applications of DFT investigations in the thermal degradation process of polymers should be highlighted in this section.

Theoretical investigations

8- The authors investigate the reaction outcomes of the thermal degradation process of Nylon 6 and Polyhydroxybutyrate using only DFT calculations. The authors must use more computational methodology such as Conceptual Density Functional Theory (DFT), the electron localization function (ELF), Non-covalent interactions (NCIs), and QTAIM analyses…

 

 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The thermal stability of polymers is one of the most important properties, which greatly affect their processing and uses. The theoretical calculations about the thermal stability of polymers are of great significance. In this manuscript, the thermal degradation of polyamide 6 and polyhydroxybutyrate is studied by means of quantum-chemical calculations, and the solvent and temperature effects of thermal degradation are discussed. The approaches of theoretical calculations are feasible and the good results are achieved. The import points are clearly described. The conclusions are supported by the data. The research accords with the scope of Physchem - Theoretical and Computational Chemistry. After minor revision, this manuscript can be accepted for publishing.

 

The following minor issues should be addressed.

 

Lines 30-31: “Nylon 6 consists six-carbon chain with amide and carboxyl functional groups; the chemical structure of nylon 6”: “consists” should be replaced by “consists of”.

 

Lines 39-40: “Polyesters, in contrast to polyamides, are a group of naturally occurring polymers; an important part of which are polyhydroxyalkanoates (PHAs)”: “Polyesters, in contrast to polyamides, are a group of naturally occurring polymers” are not correct. Polyesters may be synthetic or natural. PHAs may be naturally occurring. “an important part of which are” should be “--- of which is”.

 

Line 69: “the polymer chain bents from terminal mer”: Please check this sentence.

Line 70: “during the “crosslinking” mechanism the polymer chain bents from inside of the chain”: Please check this sentence.

 

Line 141: “peptide bond” had better be replaced by “amide bond”.

 

References:

Ref. 1: Journal name “IJSR” should be replaced by “Int. J. Sci. Res.” (International Journal of Scientific Research).

Please check the paper titles in all references, and note the consistency of case sensitivities.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

 Accept in présent form