Unsaturated Copolyesters from Macrolactone/Norbornene: Toward Reaction Kinetics of Metathesis Copolymerization Using Ruthenium Carbene Catalysts

Round 1

Reviewer 1 Report

This manuscript by Prof. Martinez et al. describes the synthesis of copolymers from macrolactone and norbornene. The influences of Ru metathesis catalysts on reactivity and polymer composition are investigated. The results of the study are valuable to researchers working in the similar field. This Reviewer recommends the acceptance of the manuscript to the Journal.

One minor issue: the author indicates that Ru1 displays superior stability relative to Ru2 and Ru3 catalysts. This Reviewer does not find any evidence throughout the manuscript, which supports this statement. The author is recommended to provide more information or to remove this supported statement.

 

Author Response

Thank you for your comments on our paper entitled “Unsaturated Copolyesters from Macrolactone/Norbornene: Toward Reaction Kinetics of Metathesis Copolymerization Using Ruthenium Carbene Catalysts” (Manuscript ID: ijms-1675354). We have carefully reviewed the comments and have revised the manuscript accordingly. Our responses are given in a point-by-point manner below.

 

Point 1. One minor issue: the author indicates that Ru1 displays superior stability relative to Ru2 and Ru3 catalysts. This Reviewer does not find any evidence throughout the manuscript, which supports this statement. The author is recommended to provide more information or to remove this supported statement.

Response 1: The stability of the Ru1-Ru3 catalysts did not was studied in this work. We opted not to include this statement.

(Page 3, Paragraph 2). Lines 137 and 138. It was changed “The catalysts Ru1 with an NHC ligand showed superior activity and stability upon catalysts Ru2 and Ru3 bearing PCy₃ ligands” by “The catalysts Ru1 with an NHC ligand showed superior activity upon catalysts Ru2 and Ru3 bearing PCy₃ ligands”

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled "Unsaturated Copolyesters from Macrolactone/Norbornene: Toward Reaction Kinetics of Metathesis Copolymerization Using Ruthenium Carbene Catalysts" is an intrresting attempt to try the very common Grubbs catalyst for polymerization for a specific copolymerization reaction. The idea behind the study is sound, as is the exectutuin of the study, although it's just one reaction catalyzed by only 3 different, very common catalyst. On the other hand authors did a good job in optimizing the reaction and trying many different reaction setups to come with some interesting results and they described their findings quite well (though there are some minor language problems in the text).

One thing I don't like is the sentence on Page 3: "It has been demonstrated by computational modeling that the free Gibbs activation energies of metathesis are consistently higher for the catalyst Ru1 than for Ru2 with better transition state stabilization by the IMesH2 ligand compared to PCy3 [1].". First, this is likely a wrong reference, since paper 1 does not provide any computational results. Second, this feature (higher activation energies of SIMes Grubbs catalysts versus PCy3 one) has been also demonstrated experimentally; for the reference please see Chapter 9 in Grubbs Handbook of Metathesis. Finally, while the sentence is true, there is no discussion (even a short one) why higher activation energies are desireable in polymerization. I would suggest expanding this part slightly and adding more references, so the reader can better understand the mechanistic details behind the expected better results obtained using 2nd generation Grubbs catalysts.

Despite the somehow limited scope I'm in favor of accepting this manuscript after the revision is made.

Author Response

Thank you for your comments on our paper entitled “Unsaturated Copolyesters from Macrolactone/Norbornene: Toward Reaction Kinetics of Metathesis Copolymerization Using Ruthenium Carbene Catalysts” (Manuscript ID: ijms-1675354). We have carefully reviewed the comments and have revised the manuscript accordingly. Our responses are given in a point-by-point manner below.

 

Point 1. One thing I don't like is the sentence on Page 3: "It has been demonstrated by computational modeling that the free Gibbs activation energies of metathesis are consistently higher for the catalyst Ru1 than for Ru2 with better transition state stabilization by the IMesH2 ligand compared to PCy3 [1].". First, this is likely a wrong reference, since paper 1 does not provide any computational results. Second, this feature (higher activation energies of SIMes Grubbs catalysts versus PCy3 one) has been also demonstrated experimentally; for the reference please see Chapter 9 in Grubbs Handbook of Metathesis. Finally, while the sentence is true, there is no discussion (even a short one) why higher activation energies are desireable in polymerization. I would suggest expanding this part slightly and adding more references, so the reader can better understand the mechanistic details behind the expected better results obtained using 2nd generation Grubbs catalysts.

Response 1: Yes, it is a wrong reference. The reference [1] has been eliminated in the paragraph 2, line 143

 (Page 3, Paragraph 2). Lines 141 to 143. It was changed “It has been demonstrated by computational modeling that the free Gibbs activation energies of metathesis are consistently higher for the catalyst Ru1 than for Ru2, with better transition state stabilization by the IMesH₂ ligand compared to PCy₃ [1].” By “It has been demonstrated that the free Gibbs activation energies of metathesis are consistently higher for the catalyst Ru1 than for Ru2, with better transition state stabilization by the IMesH₂ ligand compared to PCy₃ [37].”

 

The references section was modified. The reference [37] was added:

(Page 14). Lines 608 to 620. It was changed

“37. Mayo, F.R.; Lewis, F.M. Copolymerization. I. A Basis for Comparing the Behavior of Monomers in Copolymerization; The Copolymerization of Styrene and Methyl Methacrylate, J. Am. Chem. Soc. 1944, 66, 1594–1601. https://doi.org/10.1021/ja01237a052.

38. Fineman, M.; Ross, S.D. Linear Method for Determining Monomer Reactivity Ratios in Copolymerization, J. Polym. Sci. 1950, 5, 259–262. https://doi.org/10.1097/01241398-199509000-00028.
39. Erbil, C.; Özdemir, S.; Uyanik, N. Determination of the monomer reactivity ratios for copolymerization of itaconic acid and acrylamide by conductometric titration method, Polymer. 2000, 41, 1391–1394. https://doi.org/10.1016/S0032-3861(99)00291-8.
40. Schleyer, P.V.R.; Wiliiams, J.E.; Blanchard, K.R. Evaluation of strain in hydrocarbons. The strain in adamantane and its origin, J. Am. Chem. Soc. 1970, 92, 2377–2386. https://doi.org/10.1021/JA00711A030.
41. Hlil, A.R.; Balogh, J.; Moncho, S.; Su, H.L.; Tuba, R.; Brothers, E.N.; Al-Hashimi, M.; Bazzi, H.S. Ring opening metathesis polymerization (ROMP) of five- to eight-membered cyclic olefins: Computational, thermodynamic, and experimental approach, J. Polym. Sci. Part A Polym. Chem. 2017, 55 (2017) 3137–3145. https://doi.org/10.1002/POLA.28695.
42. Hodge, P. Entropically driven ring-opening polymerization of strainless organic macrocycles, Chem. Rev. 2014, 114, 2278–2312. https://doi.org/10.1021/cr400222p.”

by

“37. Justin R. Griffiths, J.R.; Diver, S.T.  Factors Affecting Initiation Rates. In Handbook of metathesis, 2nd ed.; Grubbs, R. H., Wenzel, A. G. Vol 2. Wiley-VCH. Verlag GmbH & Co. KGaA. Germany, 2015, Volume 2, pp. 273-279. DOI: 10.1002/9783527674107

38. Mayo, F.R.; Lewis, F.M. Copolymerization. I. A Basis for Comparing the Behavior of Monomers in Copolymerization; The Copolymerization of Styrene and Methyl Methacrylate, J. Am. Chem. Soc. 1944, 66, 1594–1601. https://doi.org/10.1021/ja01237a052.
39. Fineman, M.; Ross, S.D. Linear Method for Determining Monomer Reactivity Ratios in Copolymerization, J. Polym. Sci. 1950, 5, 259–262. https://doi.org/10.1097/01241398-199509000-00028.
40. Erbil, C.; Özdemir, S.; Uyanik, N. Determination of the monomer reactivity ratios for copolymerization of itaconic acid and acrylamide by conductometric titration method, Polymer. 2000, 41, 1391–1394. https://doi.org/10.1016/S0032-3861(99)00291-8.
41. Schleyer, P.V.R.; Wiliiams, J.E.; Blanchard, K.R. Evaluation of strain in hydrocarbons. The strain in adamantane and its origin, J. Am. Chem. Soc. 1970, 92, 2377–2386. https://doi.org/10.1021/JA00711A030.
42. Hlil, A.R.; Balogh, J.; Moncho, S.; Su, H.L.; Tuba, R.; Brothers, E.N.; Al-Hashimi, M.; Bazzi, H.S. Ring opening metathesis polymerization (ROMP) of five- to eight-membered cyclic olefins: Computational, thermodynamic, and experimental approach, J. Polym. Sci. Part A Polym. Chem. 2017, 55 (2017) 3137–3145. https://doi.org/10.1002/POLA.28695.
43. Hodge, P. Entropically driven ring-opening polymerization of strainless organic macrocycles, Chem. Rev. 2014, 114, 2278–2312. https://doi.org/10.1021/cr400222p.”

 

 

 

 

(Page 7). Lines 235. It was changed “Lewis [37] and Fineman-Ross [38]” by “Lewis [38] and Fineman-Ross [39]”

(Page 7). Lines 241. It was changed  “[39]” by “[40]”

(Page 7). Lines 243. It was changed  “[40]” by “[41]”

(Page 7). Lines 244. It was changed  “[41, 42]” by “[42, 43]”

 

 

 

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

A. Martinez et al. describes the evaluation of various Ru based metathesis catalysts in ring-opening metathesis copolymerization of w-6-hexadecenlactone and norbornene monomers. The authors screened three different Ru metathesis complexes across varying feed ratio of the monomers. The incorporation of monomers in the polymer chains were quantified by NMR analysis. The authors were able to determine the reactivity ratios of the two monomers used applying the Mayo-Lewis and Fineman- Ross methods. The authors also provided thermomechanical properties isolated copolymers. The manuscript may be interesting to readers working in this filed. However, the manuscript lacks in-depth analysis of polymer backbone based on kinetics and nmr data. Therefore, the manuscript can be accepted only after the following issues being resolved.

1. The rate of propagation of NBE is much higher than HDL. Therefore, the copolymer isolated must be either a block copolymer or gradient copolymer. However, the authors claim that the copolymer isolated are random copolymers. Authors should provide the kinetic plots for at least one copolymerization employing each Ru complexes.

2. In Table for all the copolymers, the molecular weight distribution looks too broad. Authors should explain why they are too broad and should provide GPC traces. Also please provide the theoretical MW in Table 1.

3. Procedure for the copolymerization is incomplete. Authors should provide detailed experimental procedures.

4. I am not sure the NMR assignment are correct. Please make sure the C and H are assigned properly. There should be significant NBE-NBE homopolymer sections in the polymer chains which is not shown in NMR assignment.

5. 3-bromopyridine modified Ru-catalysts are known for good initiation rate. Did the authors attempted copolymerization using this complex? What will be the outcome if functional NBE are used?

6. Scheme 1: The structure of Ru initiators is too small. Please enlarge.

7. Please combine the sections 3.1 and 3.2 and remove the section headings ‘regaents’ and

   ‘Techniques’.

8. There are several typos in the manuscript. For example the in several places ‘not’ is written as

   ‘no’. Please correct it.

9. Page 3, line 127: Replace ‘synthesized’ with ‘competed’.

10. Line 487, ‘ring opened’ should replace with ‘ring opening’

11. Line 489, ‘upon’ should replace with ‘over’.

Author Response

Thank you for your comments on our paper entitled “Unsaturated Copolyesters from Macrolactone/Norbornene: Toward Reaction Kinetics of Metathesis Copolymerization Using Ruthenium Carbene Catalysts” (Manuscript ID: ijms-1675354). We have carefully reviewed the comments and have revised the manuscript accordingly. Our responses are given in a point-by-point in the PDF file

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The manuscript is, in my opinion, ready to be published.