Relationship between Degree of Polymeric Ionisation and Hydrolytic Degradation of Eudragit^® E Polymers under Extreme Acid Conditions

Round 1

Reviewer 1 Report

Overall I think this is an interesting piece of work showing what happens to Eudragit polymers under highly acidic conditions.  I don't consider these to be really new materials as such, as they are really isolated forms of the polymers prepared for testing.  I think it should be considered as to what happens to these materials when put back into water; do they generate an acidic solution? can they be reverted to the starting materials?

Regarding the text and figures I have three main comments;

The IR spectra are very poor resolution.  Given that this data is given importance in the text better spectra should be included.  

The DSC analysis could have been undertaken using the modulated mode available on the Q2000.  This would have enabled any Tg present under the exothermic peak to be seen.  If the materials are amorphous then there should be a Tg, and it would be interesting to see where this is.  

Also with the DSC, if the modulated experiment is not done, the 2nd heating cycle of the non-modulated data presented should be included, as this may also give an idea of the Tg intrinsic to the materials.   

Author Response

Regards,

First, the authors thank the evaluators and the Academic Editor for the comments and recommendations made, which we consider very accurate to improve the quality of the work. In addition, we inform that new experiments were carried out in order to clarify several doubts and questions made by the reviewers. The responses to each comment are expressed in the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript by Linares et al. reports the treatment of commercial copolymers under extremely acidic conditions to form new materials. Overall the manuscript is good with relative techniques to support the conclusion. I suggest the authors check each figure to make sure it is clear to readers. Several other comments can be found below:

1.       The two paragraphs in the Introduction part don't provide enough information on the reason this work is important to the field and readers.

2.       The authors claimed that Eudragit has been widely applied in many fields but they didn’t make a clear statement on why they use such extreme acid condition to treat these materials? In another word, why people should care about the chemical changes during the solubilization process? This should be clearly introduced in the Introduction part.

3.       Is the hydrolytic degradation rate of each segment from Eudragit the same? For example, the three segments can be hydrolyzed at the same pH and same rate? In Figure 1 the authors should make a clearer statement on the conditions they applied e.g. the concentration of HCl, for ionization and hydrolytic degradation.

4.       Page 1 line 23: 1HNMR and 13CNMR should be ‘1H NMR and 13C NMR’. Similar errors were found in the whole text. Please check carefully.

5.       Page 4 line 114. It is NMR, not RMN. The author should also provide detailed NMR parameters including 90 o pulse, delays and etc..

6.       The resolution for the FT-IR spectra was low – please improve it.

7.       The 13C NMR spectrum of Eudragit in Figure 3A is unclear.

8.       It is surprising that the modification process can affect tacticity. I am unaware that the XRD can tell such information. Please carefully check the NMR spectra, which are the good-standard to determine tacticity, to give better support to this conclusion.

Author Response

Regards,

First, the authors thank the evaluators and the Academic Editor for the comments and recommendations made, which we consider very accurate to improve the quality of the work. In addition, we inform that new experiments were carried out in order to clarify several doubts and questions made by the reviewers. The responses to each comment are expressed in the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The changes have added beneficially to the manuscript, I have no further comments 

Reviewer 2 Report

I don't have further comments to the revision.