Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors present a highly relevant, timely, and well-structured systematic review on the transition from fossil-derived to bio-based polymer additives. The use of the PRISMA methodology ensures transparency, and the focus on recent literature (2023-2026) provides significant value to the scientific community. The manuscript is generally well-written and the scientific arguments are sound. However, there are a few formatting issues, visual missing elements, and minor inconsistencies that need to be addressed to make the paper more complete and polished. I recommend a "Major Revision" primarily to allow the authors ample time to properly adjust the figures and formatting.

• Decimal Separators in Table 2:There is a typographical error regarding the numerical formatting in Table 2. Please replace the commas (,) with periods (.) for all decimal values to align with standard English academic formatting.
• Acronym Definitions:From line 314 onwards, several acronyms for specialized molecules (e.g., PMBL, PBCL, VA8-P, DOPO) are introduced in the main text. While these are explained in Table 1, they must also be explicitly defined in the text upon their first mention to ensure smooth readability.
• Reference Typo (Zhang et al.):There is a misspelling regarding Reference [41] (Zhang et al., 2025). In Figure 4, it is incorrectly written as "Zang et al." , and this typo ("Zang et al.") is also repeated in the main text. Please correct this throughout the manuscript.
• Figure 3 Missing Legend:Figure 3 (VOSviewer network map) currently lacks a color scale legend. The caption states that the overlay color range illustrates the evolution of terms (2023-2026), but the reader cannot identify which color corresponds to 2023 and which to 2026. Please integrate the color bar (color scale legend) directly from the VOSviewer software into the image to make the map readable.
• Unit Consistency:In line 447, the text reads "11% protonated chitosan". Please change this to "11 wt% protonated chitosan" to maintain consistency with the unit formatting used in the rest of the manuscript.
• Translation Error:In line 791, the term "hidroxipropilmetilcelulose" is used. This appears to be a Portuguese/Spanish term. Please replace it with the correct English term: "hydroxypropyl methylcellulose (HPMC)".
• References Formatting: The formatting in the References section (starting from line 935) is inconsistent. Some references include a DOI while others do not, and the order of the bibliographic elements (Authors, Year, Title, Journal) varies across different entries. Please revise the entire reference list to strictly comply with the journal's specific citation style.

 

Author Response

1. Reviewer Comment: Decimal Separators in Table 2 - There is a typographical error regarding the numerical formatting in Table 2. Please replace the commas (,) with periods (.) for all decimal values to align with standard English academic formatting.

Answer:

We have corrected Table 2 as requested. All commas used as decimal separators have been replaced with periods (e.g., from "2,5" to "2.5") to adhere to standard English academic formatting.

 

2. Reviewer Comment: Acronym Definitions - From line 314 onwards, several acronyms for specialized molecules (e.g., PMBL, PBCL, VA8-P, DOPO) are introduced in the main text. While these are explained in Table 1, they must also be explicitly defined in the text upon their first mention to ensure smooth readability.

Answer:

We agree with the reviewer's assessment. All acronyms for specialized molecules (including PMBL, PBCL, VA8-P, and DOPO) are now explicitly defined in the main text at their first mention, regardless of their presence in new Table 1. This ensures a smoother reading experience without requiring constant cross-referencing.

 

3. Reviewer Comment: Reference Typo (Zhang et al.) - There is a misspelling regarding Reference [41] (Zhang et al., 2025). In Figure 4, it is incorrectly written as "Zang et al.", and this typo ("Zang et al.") is also repeated in the main text. Please correct this throughout the manuscript.

Answer:

We apologize for the oversight. The spelling has been corrected from "Zang" to "Zhang" throughout the entire manuscript, including Figure 4 and the corresponding citations in the main text, to ensure consistency with Reference [41].

 

4. Reviewer Comment: Figure 3 Missing Legend - Figure 3 (VOSviewer network map) currently lacks a color scale legend. The caption states that the overlay color range illustrates the evolution of terms (2023-2026), but the reader cannot identify which color corresponds to 2023 and which to 2026. Please integrate the color bar (color scale legend) directly from the VOSviewer software into the image to make the map readable.

Answer:

We appreciate the reviewer’s attention to detail. We apologize for the confusion caused by an error in the original manuscript's text. The original caption mistakenly described the figure as an "Overlay Visualization" (chronological), when it is, in fact, a "Network Visualization". In VOSviewer, this specific mode uses colors to represent thematic clusters based on co-occurrence strength, not a timeline. Since these clusters are qualitative groupings generated by the software's algorithm, there is no numerical "color scale" or "date legend" to be extracted from the software for this map.

To resolve this and ensure full clarity, we have:

Corrected the Figure 3 caption to explicitly state that colors identify thematic research clusters (e.g., green for bio-precursors, red for biopolymers).

Revised the Results section (Lines 203–220) to clearly define what each color represents, providing a direct link between the visual clusters and the scientific discussion.

Clarified in the text that the bibliometric growth is shown in Figure 2 (quantitative timeline), while Figure 3 is dedicated to the qualitative conceptual mapping of the field.

 

5. Reviewer Comment: Unit Consistency - In line 447, the text reads "11% protonated chitosan". Please change this to "11 wt% protonated chitosan" to maintain consistency with the unit formatting used in the rest of the manuscript.

Answer:

 

We have standardized the unit formatting throughout the entire manuscript. All instances of percentage loadings, including the mention of protonated chitosan (formerly "11%"), have been updated to "wt%" to ensure technical consistency and precision.

 

6. Reviewer Comment: Translation Error - In line 791, the term "hidroxipropilmetilcelulose" is used. This appears to be a Portuguese/Spanish term. Please replace it with the correct English term: "hydroxypropyl methylcellulose (HPMC)".

Answer:

We apologize for the language inconsistency. The term has been corrected to the proper English nomenclature: hydroxypropyl methylcellulose (HPMC).

 

7. Reviewer Comment: References Formatting - The formatting in the References section (starting from line 935) is inconsistent. Some references include a DOI while others do not, and the order of the bibliographic elements (Authors, Year, Title, Journal) varies across different entries. Please revise the entire reference list to strictly comply with the journal's specific citation style.

Answer:

We have thoroughly revised the References section to ensure stylistic consistency throughout the manuscript. All bibliographic elements (Authors, Title, Journal/Publisher, and Year) have been standardized. DOI links were added to all journal articles where available. For non-article entries, such as technical reports [12] and book chapters [58], the formatting was adjusted to align with the journal's required sequence of information.

Reviewer 2 Report

Comments and Suggestions for Authors

In response to the unsustainable and polluting issues of petroleum-based materials, the author takes bio-based materials as the main line, lists various mainstream bio-based materials, and provides a comprehensive account of their research status, material properties, and other aspects. However, there are still some issues with this manuscript that need to be addressed.

1. The scope of the topic is too broad. It is necessary to specify the areas of research for bio-based additives in terms of certain properties.
2. For the application of bio-based materials in polymers, as well as conventional biomass materials, they are quite common, and there have been reports on such comprehensive reviews. The author's originality and advancement need to be further emphasized in the manuscript.
3. In the manuscript, the author needs to clearly explain why bio-based materials can be used as plasticizers and flame retardants? What is the mechanism of its action?
4. For the examples listed by the author, the key performance and reaction mechanisms depicted in the researchers' studies need to be appropriately presented in the manuscript.
5. The chemical structure formulas of the bio-based materials mentioned by the author need to be added to the manuscript.
6. The language in the manuscript needs to be refined.

Author Response

1. Reviewer Comment: The scope of the topic is too broad. It is necessary to specify the areas of research for bio-based additives in terms of certain properties

Answer:

The authors appreciate the reviewer’s insight. We agree that a more defined scope enhances the technical depth of the review. Accordingly, we have refined the focus of the manuscript to specifically target functional additives that enhance processability and thermal/mechanical stability, the primary bottlenecks for biopolymer adoption.

We have updated the Title and the Introduction (Lines 108–123) to explicitly state this scope. The review now clearly categorizes the additives into 'Processing Aids' and 'Stability/Reinforcement Agents,' ensuring a cohesive analysis of how these bio-based solutions overcome specific engineering challenges in sustainable materials science.

 

2. Reviewer Comment: For the application of bio-based materials in polymers, as well as conventional biomass materials, they are quite common, and there have been reports on such comprehensive reviews. The author's originality and advancement need to be further emphasized in the manuscript.

Answer:

We appreciate the reviewer’s comment and have revised the Introduction to emphasize the originality of this work. Our study is designed as a systematic and chronological evolution of the foundational review by Marturano et al. (2023), specifically capturing the "molecular programming" era that emerged between 2023 and 2026. Unlike previous narrative reports, this manuscript utilizes the PRISMA methodology and bibliometric mapping to resolve recent conflicting data on bio-based additives. By focusing on the transition from passive fillers to advanced multifunctional agents, such as bio-vitrimers and phosphorylated lignin, we provide a high-resolution roadmap that represents a necessary and significant update to the existing literature.

 

3. Reviewer Comment: In the manuscript, the author needs to clearly explain why bio-based materials can be used as plasticizers and flame retardants? What is the mechanism of its action?

Answer:

The authors appreciate the reviewer’s suggestion to strengthen the theoretical framework of the manuscript. As requested, a detailed explanation of the dual-functionality mechanisms has been included in Section 3.2.1 (Lines 390–400). We have clarified that the plasticizing effect is driven by the disruption of intermolecular forces and the increase in free volume, while the flame-retardant effect results from a synergistic action between condensed-phase char formation and gas-phase radical quenching. The specific molecular designs of the additives reported by Qian et al. [37], Hou et al. [36], and Sun et al. [38] were used to illustrate these combined physical-chemical mechanisms.

 

4. Reviewer Comment: For the examples listed by the author, the key performance and reaction mechanisms depicted in the researchers' studies need to be appropriately presented in the manuscript.

Answer:

We appreciate the reviewer’s suggestion. The manuscript was revised to ensure that for each key study discussed, both quantitative results and the underlying reaction mechanisms are explicitly presented. These additions include specific data on property improvements and technical explanations of interactions such as covalent anchoring, hydrogen bonding, or steric stabilization. The changes are highlighted in the text to provide a clearer structure-property relationship while maintaining a cautious and objective scientific analysis.

 

 

5. Reviewer Comment: The chemical structure formulas of the bio-based materials mentioned by the author need to be added to the manuscript.

Answer:

 

We have addressed the reviewer’s request by incorporating Table 1, which now includes the chemical structures of the primary, discrete bio-based additives analyzed.

Regarding the broad range of materials mentioned, we have strategically selected these specific structures because they possess well-defined chemical identities that clearly illustrate the reactive mechanisms (e.g., phosphorus-nitrogen synergies, furanic stability, and aromatic reinforcement) discussed throughout the text.

For other materials cited, such as lignin, tannins, and various agro-industrial residues (e.g., wood chips or coffee grounds), providing a single chemical formula would be scientifically inaccurate due to their inherent structural complexity, high polydispersity, and compositional variability. For these cases, the manuscript focuses on their functional group density and macromolecular behavior, which are the relevant parameters for their application in polymer science. We believe this approach provides the necessary structural clarity without compromising scientific rigor.

 

6. Reviewer Comment: The language in the manuscript needs to be refined.

Answer:

The authors thank the reviewer for this suggestion. The entire manuscript has undergone a comprehensive linguistic revision. Specific improvements include:

• Syntax and Punctuation: Sentence structures were refined to improve clarity and flow, and punctuation was corrected throughout the text.
• Academic Tone: Technical terminology was standardized, and "filler" phrases were replaced with more precise academic language.
• Consistency: Units, symbols (such as T_g, M_n, and CO₂), and decimal notations were normalized to meet international publication standards.

We believe the manuscript's readability and professional quality have been significantly enhanced.

Reviewer 3 Report

Comments and Suggestions for Authors

This paper aims at reviewing recent advances on the use of bio-sourced additives in polymer materials. A recent review was published in 2023 on the same topic [DOI: 10.1016/j.pmatsci.2023.101186] and is cited. Quite expectedly, the new review focused thus on the new works published since then, thus between 2023 and to-day.

Several additives used up to now suffer severe drawbacks due to their toxicity. Besides, even tough they are present in small amounts in the polymer material, when they are released in nature and that they don’t degrade, they can slowly accumulate in nature, which brings new potential risks on the long term. There is thus a need to innovate by the discovery of additives with low toxicity and that degrades when released in the environment. In the past, many additives were synthesized from oil as a source of carbon. The  use of biomass is an opportunity to extend the range of available molecules as potential additives with low toxicity and degradation with suitable kinetics into products valorized by nature. As noted in the review, the  use of bio-sourced waste is also a route towards a circular economy. This context accounts for the publication of a review, which should raise the interest of the readership of the journal. The authors reported their strategy to collect relevant papers by using Scopus. The number of newly published papers is steadily increasing, which proves the importance of the field. The paper is clearly structured and divided into sections based on the improvement of given properties of these additives for various applications.

I have just minor remarks:

By reading the review, the reader could have the feeling that oil-based additives are automatically toxic and that bio-based additives are not, even though it is not written so directly within the text. The reality is of course more subtle because there is such a direct cause-effect correlation between the origin of the product and its toxicity. For instance, a single product can be either bio-based of oil-based depending of the process used for its synthesis. Besides, among the bio-based products, they can be either natural  or not when they are modified by chemical processes. It is also quite common that, for a product usually produced from oil, a novel synthetic process is discovered in such a way that the same product can become bio-sourced. I have the feeling that a comment could be added in the text to avoid such kind of confusion and for keeping the review rigorous scientifically.

The title used the keyword “sustainable”, which involves the three economic, social and environmental pillars. As this is usually the case, the reviews focused mainly on the environmental pillar and less on the economic and social consequences. The reviews mentioned the renewability of the resource, which is a positive point for the bio-resource, and will have an economic impact when the resource will be scarce. The current situation in the world highlights the facts that other parameters impact the availability of the resource and its price, with an obvious economical and social impact. One can not the availability of the resource in a limited number of countries, the dependence of some countries to a too limited number of countries with risks akin to the political developments and even wars. These are some tracks to deepen the economic and sustainable impact. Of course, this is not the aim of the review to develop a detailed discussion on these topics but I have the feeling that a brief comment can be useful.

The authors used acronyms, which are sometimes not very common, and are difficult to understand. Of course, the meaning of the acronyms can be found easily by reading the cited works. Nevertheless, when that situation happens, it remains useful for the reader to indicate a small explanation of a scheme with a chemical structure.

Globally, my comments should be easy to be taken into account by the authors and, accordingly,  I recommend this review for publication.

 

 

 

 

Author Response

1. Reviewer Comment: The manuscript should avoid the potential misconception that oil-based additives are automatically toxic and bio-based ones are not. The scientific reality is more subtle, as the same product can be synthesized from different sources, and chemical modifications of bio-based materials can alter their safety profiles. A comment should be added to ensure scientific rigor regarding the correlation between origin and toxicity.

Answer:

The authors would like to thank the reviewer for this insightful and scientifically rigorous observation. We fully agree that the distinction between a molecule's origin and its toxicological profile is fundamental for a balanced discussion. As suggested, we have revised the Introduction to explicitly clarify that toxicity is a function of chemical structure and not carbon source. Section 1 (Introduction, lines 80–85).

“It is important to emphasize that the toxicological profile of a molecule is defined by its chemical structure and not by its origin. Consequently, bio-based "drop-in" additives may also exhibit the same chemical behavior as their fossil-derived counterparts, and any sub-sequent functionalization of natural precursors must be carefully evaluated to ensure that performance optimization does not compromise safety. “

 

2. Reviewer Comment: Since the title includes the term 'sustainable', the review should briefly address the economic and social pillars alongside the environmental one. I suggest adding a brief discussion on resource availability, geopolitical dependencies, and how global events (such as conflicts or scarcity) impact the price and supply chain of biomass-derived additives.

Answer:

The authors agree that a holistic approach to sustainability must include socio-economic resilience. As suggested, we added a discussion in the Conclusions and Future Perspectives (lines 1010–1013) regarding the socio-economic benefits of bio-based additives. We specifically highlighted how utilizing localized biomass residues can mitigate geopolitical dependencies and supply chain vulnerabilities inherent to fossil-based resources, especially during periods of global instability.

 

“Beyond technical goals, the socio-economic pillar of sustainability must be strengthened; utilizing localized biomass residues can mitigate the geopolitical dependencies and supply chain vulnerabilities inherent to fossil-based resources, especially in contexts of global instability and resource scarcity. “

3. Reviewer Comment: The use of uncommon acronyms makes the text difficult to follow at times. While readers can find their meanings in the cited works, it would be much more helpful to provide a brief explanation or, ideally, include schemes depicting the chemical structures of the more complex additives discussed.

Answer:

We agree with the reviewer. To improve readability, we added Table 1 (Lines 241–250), which lists the acronyms, names, and structural schemes for selected representative additives discussed in the text. This selection focuses on the most complex molecules to help the reader quickly identify their molecular architecture. Additionally, we ensured that all other acronyms are defined upon their first mention throughout the manuscript.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all my concerns and successfully incorporated the requested revisions. The manuscript is now significantly improved and ready for publication. Well done.

Reviewer 2 Report

Comments and Suggestions for Authors

After the manuscript was revised by the author, its quality was improved and the current version can be accepted.