An Overview of Coacervates: The Special Disperse State of Amphiphilic and Polymeric Materials in Solution

Round 1

Reviewer 1 Report

The review by Naskar and coworkers offers an up-to-date summary of the construction and application of coacervates. This review is long and comprehensive and is potentially interesting to readers not only in the academic field but also in practical applications. However, the structure of the review needs to be revised to be more logical. Major revisions are needed before it can be considered for publication in any journals. Some detailed suggestions are as follows:

（1）    On page 6, the “Factors influencing coacervation” should be part of the contents in the “Methods used for the determination of physical chemical properties of Coacervates”.

（2）    On page 6, the factors that influence coacervation is actually very important part of this review. The several factors from (i) to (vi) from line 257 to 258 should be discussed point by point in the following section.

（3）    The classification of coacervates in the present work does not cover all kinds of important coacervates. For example, the coacervates formed by peptide or proteins are very important, but not well discussed in the present version.

（4）    There should include a Figure that describing the classification, the structure and properties and application of the coacervates, so as to help the reader grasp the main idea of the review.

（5）    The first two lines in the abstract is wrong. The dense phase is not always a lower phase.

（6）    An outline is needed.

Author Response

Comments and Suggestions for Authors

The review by Naskar and coworkers offers an up-to-date summary of the construction and application of coacervates. This review is long and comprehensive and is potentially interesting to readers not only in the academic field but also in practical applications. However, the structure of the review needs to be revised to be more logical. Major revisions are needed before it can be considered for publication in any journals. Some detailed suggestions are as follows:

（1）On page 6, the “Factors influencing coacervation” should be part of the contents in the “Methods used for the determination of physical chemical properties of Coacervates”.
Ans. We would rather retain those in their own section. General readers and young researchers can quickly get an idea of the types of methodologies being used to explore coacervates. In the section on "Factors influencing coacervation," some methods are also covered with examples.

（2）On page 6, the factors that influence coacervation is actually very important part of this review. The several factors from (i) to (vi) from line 257 to 258 should be discussed point by point in the following section.
Ans. According to the suggestion factors influencing coacervation (i) to (vii) have been separated by mentioning the proper section in the revised manuscript. Please see pages 9 to 14.  Some addition is also done on page 14.

（3）The classification of coacervates in the present work does not cover all kinds of important coacervates. For example, the coacervates formed by peptide or proteins are very important, but not well discussed in the present version.

Ans. Coacervate is fairly a diverse field. Various kinds of work have been done over time. In this review, we presented a succinct overview of the coacervates along with the influencing factors of their formation, the development of theory to understand their complexity, and their applications in different fields. It's true that this review makes mention of a few coacervate systems involving biological molecules. It is challenging to cover all types of examples due to space restrictions. Indeed, protein and peptide-based coacervates are extremely useful in the field of medicine. A section has been added in the name of peptide/protein type under complex coacervate. This is presented on pages 26 - 27.

（4） There should include a Figure that describing the classification, the structure and properties and application of the coacervates, so as to help the reader grasp the main idea of the review.
Ans. A schematic diagram with detailed descriptions has been added at the end of the summary on page 33.

（5） The first two lines in the abstract is wrong. The dense phase is not always a lower phase.

Ans. The necessary modification of the statement has been made. Please see page 1.

 

 (6) An outline is needed.

Ans. Content has been added after the abstract. This is presented on pages 1 and 2.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript provides a review of coacervates, which are systems of dense colloidal systems in liquid phase in thermodynamic equilibrium with dilute colloidal solutions. The manuscript first introduces the general concept of coacervate, then discusses qualitatively the theories of the formation of coacervates. This followed by a discussion of the factors affecting the formation of coacervates (such as ionic strength, concentration, and in general phase diagrams). Examples of both simple and complex coacervates are discussed, before dealing with the applications. The manuscript is well written and well structured. It is a useful and enjoyable introduction to coacervates. Some additional discussion in the introduction about the difference between coacervates and precipitates should however be welcome, because for the unexperienced reader, for whom the review is meant, this is an interesting aspect. Furthermore, the modeling part is too qualitative. Some quantitative aspect might be interesting to the general readership.

Author Response

This manuscript provides a review of coacervates, which are systems of dense colloidal systems in liquid phase in thermodynamic equilibrium with dilute colloidal solutions. The manuscript first introduces the general concept of coacervate, then discusses qualitatively the theories of the formation of coacervates. This followed by a discussion of the factors affecting the formation of coacervates (such as ionic strength, concentration, and in general phase diagrams). Examples of both simple and complex coacervates are discussed, before dealing with the applications. The manuscript is well written and well structured. It is a useful and enjoyable introduction to coacervates. Some additional discussion in the introduction about the difference between coacervates and precipitates should however be welcome, because for the unexperienced reader, for whom the review is meant, this is an interesting aspect. Furthermore, the modeling part is too qualitative. Some quantitative aspect might be interesting to the general readership.

 Ans. The suggestion of additional information about the phenomena coacervation and precipitation and their difference for the readers has been considered. This is presented on pages 11-12.

            The quantitative aspects of the modeling of coacervates have not been the aim of our review. In Sec.1 (Perspective), we have discussed about the coacervates, their shapes, types, functions, etc. qualitatively.  In Sec. 2 (The theories), quantification approach of the coacervation process has been attempted in energetics terms, in some details. The changes and additions made are presented on pages 5-8.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have adequately addressed all my concerns, and the paper should now be accepted after a little more attention is given to grammatical errors.