Novel Copper-Based Catalytic Systems for Atom Transfer Radical Polymerization of Acrylonitrile

Round 1

Reviewer 1 Report

The article titled "Novel Copper-Based Catalytic Systems for Atom Transfer Radical Polymerization of Acrylonitrile" by Ivan D. Grishin, Elizaveta I. Zueva, Yulia S. Pronina and Dimtry F. Grishin is a collection of information on the contemporary popular topic of Atom Transfer Radical Polymerization. The article was written based on 25 references which are quite fresh. References have been selected correctly. The authors have prepared very aesthetically pleasing drawings in their article, which make it easier to read the whole article and understand the issues raised. The research methodology for polymers was well chosen. The advantage of the article is the fact that the authors performed a wide range of experimental work.

However, I have a few comments on the article, which will improve the article as a whole and make it even more interesting for readers of "Catalysts". 

1. The introduction lacks specific data on copper-based catalytic systems for atom transfer radical polymerization, e.g. catalytic activities, TOF and TON numerical values.

2. Scheme 1. The mechanism of AGRET ATRP - here, the symbols used in the diagram should be explained, e.g. Pm, Pn, Hal, kp

3. On the basis of the kinetic plots, an attempt should be made to determine the order of the tested reactions

4. The work should include a scheme/equation of ATRP acrylonitrile polymerization reaction

5. The article lacks the physicochemical characteristics of the new copper (II) bromide complexes as catalytic systems

6. An explanation should be added why acrylonitrile was chosen as the monomer for the studied polyemrization.

Author Response

We are thankful for reviewer for careful reading of our paper and valuable comments and remaks. The paper was corrected. The detailed answers are provided below.

1. The introduction was improved in accordance with reviewer’s recommendation. Some additional information about ATRP was added. At the same time it should be noted that the terms TON and TOF are not applicable for ATRP process. The number of catalytic cycles or interactions of radical with copper complex does not exactly match number of added monomer units.
2. The Scheme 1 is corrected.
3. According to the mechanism and the actual theory of ATRP process, the reaction should have first order on monomer concentration. The linear kinetic plots on figure 1 confirm this proposition. At the same time some deviations from linear kinetic plots is observed on figure 2. This was mentioned in the text.
4. The general scheme of the process is shown on scheme 1. The polymerization of AN proceeds in a same way M=Acrylonitrile. We suppose the doubling of the scheme is excessive, especially after addition of comments to scheme 1.
5. Theses complexes are not novel and are well-studied in a previous works. The corresponding references are added in the text. These compounds were obtained in situ by interaction of copper bromide with corresponding nitrogen-based ligand. The detailed study seems excessive. The novelty of the work is the application of these systems for acrylonitrile polymerization, the use of RS as a reducing agent and tandem use of catalysts .
6. The explanation of the interest in acrylonitrile polymerization was added to the text.

Reviewer 2 Report

After read carefully this present manuscript, I would like to recommand this article for publication in your journal Catalyst, of course after some modifications and answers to my questions:

1) I would like to understand why the authors do not use CCl3Br instead CCl4 (in fact its known as a starting point of the ATRA method in organic chemistry).

Maybe they can try some experiments by using this compound.

2) It is possible to find a reference to point out the fact of specificity of PMDTA as ligand for Cu2+ ? If you have please add one. (please do not forget to indicate the full name of PMDTA in the paragraph 2.1)

3) It should be interesting to characterize Cu-PMDTA complexes by FT-IR ? They could also explain why they used TPMA and PMDTA as the main ligands in the entire work, instead of Me6TREN or BPy and its more soluble derivatives).

4) DMSO is also recognize in organic chemistry as an oxidizing agent. There is not bad effect on the result ? The author should try at least one time the same reaction with another polar solvent such as DMF or CH3CN.

Author Response

We are thankful for reviewer for careful reading of our paper and valuable comments and remaks. The paper was corrected. The detailed answers are provided below.

1. CCl4 is known for its ability to initiate ATRP reaction. It is cheap and available chlorine-based initiator. The proposed idea of the use of CCl₃Br is interesting. We are thankful to reviewer for this comment and will test this initiator later. Unfortunately, we can’t provide full experiment with CCl₃Br to add to this paper in a limited time as we need to purchase a compound, provide polymerization experiments and analyze samples by SEC.
2. A required reference was added to the text.
3. This idea is really interesting, but in our opinion it is excessive, as the compounds are already known and its UV-vis spectra confirm its formation. The idea of the work was to test PMDTA as one of the ligands for acrylonitrile polymerization. Me₆TREN forms too active complex with copper that results in the loss of control over the process. Complex with bipy is less active. These compounds were studied by us earlier. See ref [18].
4. The reviewer is right. DMSO may be considered as oxidizing agent, but a rather weak one. It’s reduction should lead to the formation of sulfur or sulfides. We have not observed these products. We have tested DMF as a solvent, but it has poor performance. The use of CH3CN is impossible, as it does not dissolve polyacrylonitirile.

Round 2

Reviewer 1 Report

The authors have improved the manuskyrpt very well. In my opinion, manuscrpt in current form can be published in Catalysts journal.

Reviewer 2 Report

After read their responses, I consider they have perfectly answered to my questions and I would like to recommend this article for publication under this present form.