Li et al. prepared PEG/P (U-AM-ChCl) composite hydrogel by light polymerization. The effects of PEG content on the swelling, mechanical and fatigue properties of composite hydrogels were studied. The hydrogel with 1wt% PEG was added to obtain enhanced compressive strength and fatigue strength, as well as excellent swelling performance and self-healing performance. Although the author conducted detailed experiments and data analysis, there are still many issues in the manuscript that need further supplementation and analysis.
1. It is mentioned in the abstract that the compressive strength, swelling property and self-healing ability of the hydrogel with 1wt% PEG have been greatly improved. Why are different performances analyzed based on the amount of 1wt% added? Different contents should have different effects on different performance, and choosing the same amount of addition may not be the optimal solution. In other words, adding different contents should study different performance separately and then choose the optimal solution.
2. The introduction mentions the preparation of polymerizable DES by mixing urea (U), acrylamide (AM), and choline chloride (ChCl) in a molar ratio of 1:1:1. Why choose this ratio? Is there any other better ratio?
3. In the subheadings of the second section titled "2 Materials and methods", there is an error in the subheadings, such as "3.2 Materials", "3.2 Preparation of deep European solutions", "3.2 Preparation of deep European solutions", "3.2 Preparation of deep European solutions", "2.1 SEM Characterization", "2.2 Hydrogel Swelling property test", "2.3 Testing of hydrogel mechanical properties" and "2.4 Hydrogel fatigue resistance testing". The order is chaotic, without 3.1, starting directly from 3.2, and the order is also incorrect, indicating that it is not rigorous enough.
4. In the introduction of the content of SEM characterization, it was mentioned that the hydrogel was cut into 1-3mm thick discs and soaked in deionized water for 7 days. The time required for the preparation of the product was too long, so there was no advantage? If soaking for 7 days is only necessary for testing SEM, and the tested sample is no longer in its original shape or the material has deteriorated, will the test results be accurate?
5. In Table 1, why only the wt% of PEG is changed in PEG, MBA, and TPO-L, while the other two substances remain unchanged. Is there any basis for taking 1.0 and 0.5 wt% of the other two substances, respectively?
6. Figure 4 shows the infrared spectra of P (U-AM ChCl) and PEG/P (U-AM ChCl), but only LP1, LP2, LP3, and LP4 are labeled in the figure. Unable to distinguish which is the infrared spectrum of P (U-AM ChCl) and which is the infrared spectrum of PEG/P (U-AM ChCl)? It cannot be distinguished from Figure 4 alone, please explain?
7. Is the punctuation " , " or the initial letter of "This" used incorrectly in the first paragraph of section 3.4? Such as ‘With the increase of PEG content, the hydrogen bonding density of the hydrogel was increased36, This physical crosslinked network becomes more complex and stable,’
8. There is not much difference in the compression stress-strain curves between the 10 cycles of c and d in Figure 6. It's not very obvious which one is smoother? And the horizontal axis is a time unit, not a strain unit.
9. Why is the maximum compression deformation set to 80% based on what considerations? How about performance exceeding 80%? Does the hydrogel performance fail when it exceeds 80%?
10. Why only select 10 cycles, what about 100 cycles and 1000 or even 10000 cycles? Including swelling and compressive strength. Only 10 cycles show that hydrogel has excellent fatigue resistance, which is too far-fetched.
11. What are the advantages of the hydrogel prepared in this manuscript compared with other hydrogels of the same type published recently? Can you compare it with recent publications?
12. The hydrogel rotation described in this manuscript can be maintained for a long time without performance degradation under ambient condition?
13. The degree of healing of the hydrogel can reach 91.93% within 48 hours. Is the healing time too long. It takes so long to heal, it's difficult to meet the requirements of rapid recovery in practical applications, so this performance doesn't have much advantage.
14. What advantages do you think PEG/P (U-AM-ChCl) composite hydrogel has in application? Can you provide some practical examples in the manuscript?