Copolymerization of Norbornene and Methyl Acrylate by Nickel Catalyst Bearing 2-(Diarylphosphino)-N-phenylbenzenamine Ligands
Round 1
Reviewer 1 Report
Good piece of work. All the experiments and characterizations are thorough and properly done.
Catalysts system reported here is similar to their previous work (Macromolecules 2022, 55, 9, 3513–3521), but its good to see the effect of different substituents.
Along with their previous systems, authors can compare the performances of their current system with other important nickel-based catalysts used in this copolymerization (may be in a table form) to help the readers understand where the current system stands.
Determination of parameters such as ‘rate of monomer insertion’ and ‘rate of chain termination’ from the obtained analytical data and using these parameters to compare the reactivities of the catalytic systems can help to understand these systems better. Refer to : https://doi.org/10.1021/om500345r; https://doi.org/10.1021/om4006998.
Author Response
Good piece of work. All the experiments and characterizations are thorough and properly done. Catalysts system reported here is similar to their previous work (Macromolecules 2022, 55, 9, 3513–3521), but it’s good to see the effect of different substituents.
Thank you so much for your comments. Answers for the corresponding questions are as follows.
- Along with their previous systems, authors can compare the performances of their current system with other important nickel-based catalysts used in this copolymerization (may be in a table form) to help the readers understand where the current system stands.
Answer: According to the reviewer’s comment, we have compared the copolymerization performances with other catalyst systems, and the discussions were added in the revision as follows:
“It should be noted that palladium catalysts bearing [N,N]-type ligands have been reported to produce NB/MA copolymers with high MA incorporation up to 82 mol% [31,32], while few nickel catalysts achieved the copolymerization of norbornene and MA. The bis(N-acylated imidazolin-2-imine) nickel catalyst can promoted the copolymerization of norbornene and MA with similar activity and molecular weight of present nickel catalyst to produce copolymers with much lower MA incorporation (1.13–2.54 mol%)”
- Determination of parameters such as ‘rate of monomer insertion’ and ‘rate of chain termination’ from the obtained analytical data and using these parameters to compare the reactivities of the catalytic systems can help to understand these systems better. Refer to: https://doi.org/10.1021/om500345r; https://doi.org/10.1021/om4006998.
Answer: The monomer insertion rate (Ri) and chain termination rate (Rt) were calculated according to the two reported papers. Detailed discussion on these parameters of Ni1, Ni2 and Ni-Me was added in the revision as follows, and the two references have also been cited:
“The monomer insertion rate (Ri) and chain termination rate (Rt) were calculated according to the references reported by Eisen et al. [29,30]. At 80 oC, the Ph-substituted Ni1 has a Ri value of 16.57 mmol/h and a Rt value of 1.68 μmol, while Ni2 has a lower Ri value of 7.65 mmol/h and Rt value of 0.69 μmol (entries 9 and 13). In contrast, previously reported Ni-Me exhibited much higher Rt value of 5.80 μmol to produce low molecular weight polynorbornene (entry 14)”
Reviewer 2 Report
1. It is better to add a brief explanation about the catalysts (I - IX) in chart 1.
2. There are seven references to Zhengguo Cai in the sources. This number of self-references is high. The author should give a maximum of 5 references to his articles.
3. To compare two catalysts, the polymerization conditions must be the same. In Table 1, catalysts Ni1 and Ni2 performed polymerization at 25 °C, but Ni-Me at 20 °C. Please report the results under completely identical polymerization conditions.
4. Why are the DSC curves not presented in the article? Please insert it into the main text of the article.
5. Can you provide NMR spectra for copolymers?
Author Response
- It is better to add a brief explanation about the catalysts (I - IX) in chart 1.
Answer: According to the reviewer’s comment, we have added brief explanation of these catalysts was added in the revision as follows:
“As shown in Chart 1, nickel catalysts bearing the familiar N^N type α-diimine (I) [14-16], N^O type β-ketoamine (II) [17,18], aniline-anthraquinone (III) [13], imidazolidin-2-imine (IV and V) [7,8] and N-heterocyclic carbene ligands (VI and VII) [19,20], as well as P^O type phosphino-phenolate ligands (VIII) [21] have been reported for the (co)polymerization of NB and polar monomers”.
- There are seven references to Zhengguo Cai in the sources. This number of self-references is high. The author should give a maximum of 5 references to his articles.
Answer: We have reduced the references to Zhengguo Cai in the sources.
- To compare two catalysts, the polymerization conditions must be the same. In Table 1, catalysts Ni1 and Ni2 performed polymerization at 25 °C, but Ni-Me at 20 °C. Please report the results under completely identical polymerization conditions.
Answer: The norbornene polymerization results of catalyst Ni-Me (entries 14 and 15, Table 1) have been reported in our previous work (Macromolecules 2022, 55(9), 3513–3521), and the results obtained at 20 °C and 80 °C were selected to make comparisons, while Ni1 and Ni2 catalysts were tested at 25–80 oC in the current work. In order to have the same polymerization condition according to the reviewer’s comment, the comparisons among three catalysts was discussed based on the same polymerization condition obtained at 80 oC.
- Why are the DSC curves not presented in the article? Please insert it into the main text of the article.
Answer: DSC curves of obtained copolymers have been added in the revision as shown in Figure 5.
- Can you provide NMR spectra for copolymer？
Answer: The NMR spectra of all the NB/MA copolymers were added in the revision.
Reviewer 3 Report
In this contribution, the authors report on the synthesis of novel Ni complexes bearing 2-(Diarylphosphino)-N-phenylbenzenamine ligands and on their use as (pre)catalysts for the norbornene polymerization and norbornene/methyl acrylate copolymerization. Structure/activity relationships as well as the influence of the polymerization conditions on the outcome of the process have been investigated. The novel catalysts exhibited lower activities than the previously reported bis(phenyl)phosphino-N,N-dimethylaniline nickel complex, albeit allowing for higher polymer Mn.
I believe the information featured in the manuscript might be of interest for the readers of catalysts, hence I recommend its publication.
Minor points to address:
Mind the spelling of “MALDI-TOF”
In the table captions as well as in the experimental part, please indicate the amount of monomer(s) both in mmol and in g.
I believe the sentence “Research grade ethylene was purified by dehydration column of ZHD-20 and deoxidation column of ZHD-20A” could be removed from the experimental section.
Please check the section concerning the norbornene co-polymerization section of the experimental part. Aside from some typos, it is not clear how much monomer is employed and how the catalyst is prepared (i.e. are the Ni complex and MAO pre-mixed and then injected?).
Indicate “catalytic amount” of DMAP and NaH used in the synthesis of tert-butyl N-(2-bromophenyl)-N-phenylcarbamate?
Author Response
Minor points to address:
- Mind the spelling of “MALDI-TOF”
Answer: The spelling of this word has been corrected.
- In the table captions as well as in the experimental part, please indicate the amount of monomer(s) both in mmol and in g.
Answer: The amount of monomers has been revised both in mmol and in g.
- I believe the sentence “Research grade ethylene was purified by dehydration column of ZHD-20 and deoxidation column of ZHD-20A” could be removed from the experimental section.
Answer: This sentence has been removed from the text.
- Please check the section concerning the norbornene co-polymerization section of the experimental part. Aside from some typos, it is not clear how much monomer is employed and how the catalyst is prepared (i.e. are the Ni complex and MAO pre-mixed and then injected?).
Answer: The norbornene copolymerization section has been revised, and more details have been added in the revision.
- Indicate “catalytic amount” of DMAP and NaH used in the synthesis of tert-butyl N-(2-bromophenyl)-N-phenylcarbamate?
Answer: The catalytic amount of DMAP is 0.25 mmol (0.025 eq.) and the amount of NaH is 10 mmol (1.0 eq.). These details were added in the revision.
