Hydrophobic, Durable, and Reprocessable PEDOT:PSS/PDMS-PUa/SiO₂ Film with Conductive Self-Cleaning and De-Icing Functionality

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is well-written and offers research that is based on strong science. The design, analysis, and interpretation of the experiment are all good, and the data back up the conclusions. I think it adds something important to the field of PEDOT:PSS-based film electronics materials.

1. Due great conductivity, is waterproof, and is stable in the environment, please include the use of the produced composite film together with the minimal requirements that were appropriate for it. 

2. Include a comparison table that shows how this study compares to other related research, with a focus on important performance criteria and possible uses.

3. Figure 3a indicates that the error bars for each result are very high, suggesting that the obtained data may be unreliable.

4. What are the consequences of utilizing 5% or 7.5% IPA in the experiment, considering that increased IPA concentration renders the film brittle?

5. Surface roughness is a critical parameter for PEDOT:PSS-based electronic films, particularly in film electronics, since it can substantially influence their electrical, optical, and mechanical properties. Kindly provide the facts pertaining to the PEDOT.PSS-derived electronic films surface roughness value

6. Mechanical durability is a significant quality of the film. Kindly include the data on the flexibility, tensile strength, and fatigue resistance of the modified film.

Author Response

Response to the reviewers’ comments

Firstly, we deeply appreciate the reviewers for their hard work on our manuscript. Those comments are all valuable and very helpful for revising and improving our paper, as well as with important guiding significance to our future research. Below you will find our point-by-point response to the reviewers’ comments (Responses are marked in blue, and sentences revised in the manuscript are marked in red):

************************************************************************************************

Reviewers’ comments:

Reviewer #1:

1. Due great conductivity, is waterproof, and is stable in the environment, please include the use of the produced composite film together with the minimal requirements that were appropriate for it.

Response: Thank you for this comment. As your seen, the composite film developed in this article is to realize the possible uses of PEDOT:PSS based materials in self-cleaning coatings, antistatic coatings, and de-icing coatings, etc. Based on your suggestion, we have further emphasized these uses and included the minimum applicable requirements in the revised Results and discussion section.

Moreover, we modified the “Abstract”, “3.4.1. Thermostability”, and“3.4.5. De-icing capability” sections to provide more performance indexes. The revised contents are as follows:

Section “Abstract”:

“Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) stands out as a renowned commercial conducting polymer composite, boasting extensive and promising applications in the realm of film electronics. In this study, we have made a concerted effort to overcome the inherent drawbacks of PEDOT:PSS films (especially, high moisture absorption, mechanical damage vulnerability, insufficient substrate adhesion ability, etc.) by uniformly blending them with polydimethylsiloxane polyurea (PDMS-PUa) and silica (SiO₂) nanoparticles through a feasible mechanical stirring process, which effectively harnesses the intermolecular interactions, as well as the morphological and structural characteristics, among the various components. The Si−O bonds within PDMS-PUa and the –CH₃ groups attached to Si atoms significantly enhance the hydrophobicity of the composite film (as evidenced by a water contact angle of 132.89° under optimized component ratios). Meanwhile, SiO₂ microscopically modifies the surface morphology, resulting in increased surface roughness. This composite film not only maintains high conductivity (1.21 S/cm, in contrast to 0.83 S/cm for the PEDOT:PSS film) but also preserves its hydrophobicity and electrical properties under rigorous conditions, including high-temperature exposure (60-200 °C), ultraviolet (UV) aging (365.0 nm, 1.32 mW/cm²), and abradability testing (2000 CW abrasive paper, drag force of approximately 0.98 N, 40 cycles). Furthermore, the film demonstrates enhanced resistance to both acidic (1 mol/L, 24 h) and alkaline (1 mol/L, 24 h) environments, along with excellent self-cleaning and de-icing capabilities (−6 °C), as well as satisfactory adhesion (Level 2). Notably, the dried composite film can be re-dispersed into a solution with the aid of isopropanol through simple magnetic stirring and the sequentially coated films also exhibit good surface hydrophobicity (136.49°), equivalent to that of the pristine film. This research aims to overcome the intrinsic performance drawbacks of PEDOT:PSS based materials, enabling them to meet the demands of complex application scenarios in the field of organic electronics while endowing them with multifunctionality.”

Section “3.4.1. Thermostability”:

“In order to ascertain the impact of PEDOT:PSS/PDMS-PUa/SiO₂ film under extreme conditions, it was subjected to different temperatures (60-200°C) within two hours, during which time the change in the values of WCA and conductivity was being monitored (Figure 5a). With the change in temperature originating at 60°C, the WCA of PEDOT:PSS/PDMS-PUa/SiO₂ film first decreases from 119.7° to 94.5°, then increases at 120 °C, and then changes slightly. In comparison, the WCA of PEDOT:PSS film exhibits a downward trend that is relatively stable. For the reason, as the temperature increases, the molecular chain movement of PDMS-PUa intensifies, which may result in an enlargement of the gaps between molecular chains of PEDOT:PSS/PDMS-PUa/SiO₂, thereby affecting the hydrophobicity of the film to a certain extent. Furthermore, an elevation in temperature may lead to the formation of micropores or cracks within the film, affecting its surface roughness and hydrophobicity [43]. As the temperature rises, the overall conductivity of the PEDOT:PSS film shows a decreasing trend, whereas the conductivity of the PEDOT:PSS/PDMS-PUa /SiO₂ composite film exhibits an initial decline followed by a subsequent increase. The elevated temperature can result in a structural rearrangement of the PEDOT:PSS film, accompanied by a rearrangement of PEDOT [58], which shrinks the PSS region and increases conductivity (1.63 S/cm).”

Section “3.4.5. De-icing capability”:

“To better adapt to the cold weather application, we simulated the change in the film under freezing conditions (−10 °C-0 °C). The PEDOT:PSS film itself is hydrophilic and undergoes a process of swelling upon contact with a water drop, followed by condensation into ice (Figure 5h). Consequently, the film surface would be irreversibly damaged when the ice on the surface of PEDOT:PSS is removed. The PEDOT:PSS/PDMS-PUa/SiO₂ film displays excellent hydrophobic properties, thereby affording effective protection to the film, as shown in the Figure 5i. Once ice forms on its hydrophobic surface, the adhesion between the ice and the coating surface is much lower than that on an ordinary surface. This is because the microstructure and low surface energy characteristics of the hydrophobic surface make it difficult for the ice to adhere firmly [66]. When a relatively small external force is applied, the ice is more likely to detach from the hydrophobic surface. So, PEDOT:PSS/PDMS-PUa/SiO₂ film has the potential to be applied as conductive coatings that should be working under low-temperature environments.”

2. Include a comparison table that shows how this study compares to other related research, with a focus on important performance criteria and possible uses.

Response: Based on your suggestion, we have added a comparison table of relevant studies on the hydrophobicity adjustment of PEDOT:PSS in the “Introduction” section, and supplemented related discussion. In the revised version, the modified content is as follows:

“To facilitate the transformation of PEDOT:PSS from hydrophilic to hydrophobic, the introduction of specific modifiers is necessary. PEDOT:PSS inherently exhibits strong hydrophilicity, primarily due to the presence of –SO₃^– groups in PSS [30]. To alter its surface properties, chemical modification of PEDOT:PSS is necessary to reduce or eliminate these hydrophilic groups. Commonly used methods include introducing hydrophobic groups, employing surfactants, or altering their surface energy through blending. However, current research on PEDOT:PSS aqueous solutions has found that it was difficult to alter its properties by introducing other chemical groups. Instead, most studies opt for physical blending methods to enhance the properties of PEDOT:PSS films [31−33]. PEDOT:PSS constitutes a water-based system, whereas the majority of hydrophobic polymers are insoluble in water. Consequently, identifying a compatible substance that can effectively impart hydrophobicity to PEDOT:PSS while maintaining its electrical capability presents a significant challenge (Table 1) For example, our group has found that, polyhedral oligomeric silsesquioxane (POSS), which has small nano size, cage structure, easy doping of polymer materials, enhanced thermal stability, surface hardening, hydrophobicity and other properties [34], can weaken the hydrophilicity of PEDOT:PSS system and enhance its mechanical flexibility [35]. And, after the further introduction of waterborne epoxy resin and silane coupling agent, the adhesion, hardness and wear resistance of PEDOT:PSS based film to the glass substrate can be improved by forming much highly crosslinked network structure [36]. Additionally, in the field of solar cells, the hygroscopicity and acidity of PEDOT:PSS, when used as a hole transport layer, are key factors affecting the stability of the cells. To address this issue, Ma et al. introduced a hydrophobic perfluorosulfonic acid copolymer (Nafion) into PEDOT:PSS via a spin-coating process. The resulting composite films exhibited hydrophobicity (107°), chemical stability, and mechanical stability, leading to a marked improvement in device stability [37]. However, the hydrophobicity in these research is insufficient to support the promising uses of PEDOT:PSS based film in fields like self-cleaning, corrosion resistance, anti-icing, anti-fogging, drag reduction and oil-water separation [38,39], and the film durability is not studied in depth.”

Table 1. Study on the hydrophobicity of PEDOT:PSS-based films

Material	Conductivity	WCA	Application	Ref.
PEDOT:PSS/POSS	0.402 S/cm	79°	Antistatic film	[35]
PEDOT:PSS/Epoxy/POSS/SCA	104 Ω cm	87°	Antistatic film	[36]
PEDOT:PSS-Nafion	/	107°	Solar cells	[37]
This work	1.21 S/cm	132.89°	Hydrophobic coating	/

[35] Xin, X.; Yu, J.R.; Gao, N.; Xie, X.W.; Chen, S.; Zhong, J.; Xu, J.K. Effects of POSS composition on PEDOT:PSS conductive film. Synth. Met. 2021, 282, 116947.

[36] Li, Z.Q.; Xie, X.W.; Zhou, M.; Zhu, L.; Fu, C.Q.; Chen, S. High water-stable, hard and strong-adhesive antistatic films from waterborne PEDOT:PSS composites. Synth. Met. 2023, 293, 117290.

[37] Ma, S.; Qiao, W.; Cheng, T. Optical–electrical–chemical engineering of PEDOT:PSS by incorporation of hydrophobic nafion for efficient and stable perovskite solar cells. ACS Appl. Mater. Interfaces, 2018, 10(4): 3902-3911.

3. Figure 3a indicates that the error bars for each result are very high, suggesting that the obtained data may be unreliable.

Response: Based on your notice, we have rechecked the raw data and corrected the calculation error. And to make sure these results again, we tested these data again by taking much more attention to control factors that may cause errors (including sample preparation time, drying speed and temperature, testing time, size of film, etc.). At last, the revised version of Figure 3 is as follows:

 

4. What are the consequences of utilizing 5% or 7.5% IPA in the experiment, considering that increased IPA concentration renders the film brittle?

Response: Thank you for your question. Indeed, previously, we have found that when the IPA volume ratio was 8%, the conductivity of the composite film decreased (approximately 0.9 S/cm). The reason may be that a lower IPA concentration than 10 v/v% could lead to uneven distribution of PEDOT-rich agglomerates in the composite system, insufficient optimization of PEDOT chain conformation, and thus a decrease in conductivity. Relevant literature can be referred to: http://dx.doi.org/10.1016/j.solener.2016.08.023, a new citation numbered as [46] in the revised “References” section. In the revised manuscript. we have modified related representation in the section of “3.2.1. Color and UV-vis absorption spectra”, as follows:

“As illustrated in Figure 3a, when the IPA volume ratio  is 10%, the PEDOT:PSS dispersion exhibits uniform morphology, with the highest conductivity (1.21 S/cm) and WCA (132.39°). Nevertheless, when the IPA concentration is excessively high, the film is insufficiently thick and fragile. However, when the volume ratio of IPA is lower than 10%, it will lead to an uneven distribution of PEDOT-rich agglomerates in the system and insufficient conformational optimization of the PEDOT chain, thus resulting in a decrease in electrical conductivity [46]. For example, when the IPA volume ratio was 8%, the conductivity of the composite film decreased to approximately 0.9 S/cm. On the other hand, the addition of DMSO can facilitate the dispersion of the PEDOT chain and reduce the PSS wrapping between PEDOT, thereby improving the conductivity of PEDOT:PSS [47-49]. In this study, we chose to add 5% (v/v) DMSO to achieve the optimal conductivity, which have been widely known in this filed [47]. As both PDMS-PUa and SiO₂ contain Si-O bonds, they can be dispersed in IPA to form a uniform mixture and to prepare blue films. Therefore, in the following experiments, PEDOT:PSS/DMSO (5%)/IPA (10%) will be selected as the object. From the UV-vis absorption spectra, it can be seen that there is a strong absorption peak near 654 nm, which is due to the dioxane group reducing the energy barrier of the polythiophene structure (Figure 3b) [50].”

[46] Abdel-Fattah, T.M.; Younes, E.M.; Namkoong, G.; El-Maghraby, E.M.; Elsayed, A.H.; Abo Elazm, A.H. Solvents effects on the hole transport layer in organic solar cells performance. Sol. Energy, 2016, 137, 337-343.

5. Surface roughness is a critical parameter for PEDOT:PSS-based electronic films, particularly in film electronics, since it can substantially influence their electrical, optical, and mechanical properties. Kindly provide the facts pertaining to the PEDOT.PSS-derived electronic films surface roughness value.

Response: You are right that the variations in the surface roughness of thin films may significantly influence their electrical, optical, and certain mechanical properties, particularly concerning film transmittance, adhesion, and interfacial strength. We have provided AFM images along with corresponding roughness measurements for both PEDOT:PSS and PEDOT:PSS/PDMS-PUa (30 wt.%)/SiO₂ composite thin films (Figure 2). For details, please refer to Section “3.1. Structure and morphology analysis of PEDOT:PSS/PDMS-PUa/SiO₂ films”.

6. Mechanical durability is a significant quality of the film. Kindly include the data on the flexibility, tensile strength, and fatigue resistance of the modified film.

Response: You are absolutely correct. Mechanical durability is an important characteristic of thin films and a crucial criterion for measuring their stability and quality. However, based on this work, the main purpose is to promote the promising application of hydrophobic coatings on substrate surfaces (such as glasses, metals, plastics, woods, etc.), and there may not be a high requirement for the flexibility and  stretchability testing of them. This is also because there are well-known and inevitable  trade-off among the electrical, mechanical and other properties of PEDOT:PSS based films. But in other work, we indeed have considered combining the hydrophobic properties and flexibility of PEDOT:PSS films (as shown in the following figure), and are committed to developing towards flexible electrochromic  display films (https://doi.org/10.1016/j.cej.2024.154959). However, due to the difficulty in coordinating hydrophobicity and flexibility, the effect is mediocre, which is also the direction we will strive for in the future.

 

Figure. (a) The stress-strain curve and (b) elongation at break and fracture, and water contact angle of a composite film. (from Chemical Engineering Journal, 2024, 497, 154959)

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript by Fang et al. aims to enhance certain properties of PEDOT:PSS films to improve their practical applicability. By incorporating SiO₂ nanoparticles and PDMS-PUA into PEDOT:PSS, the authors significantly increased the hydrophobicity of the composite film. They demonstrated that the fillers form a lotus-leaf-like surface structure, which contributes to the film's hydrophobic behavior.

While this study falls within the scope of Coatings, several revisions are necessary before the manuscript can be accepted for publication:

1. Figures 3c and 3d are referenced in the text but are absent from the manuscript. The description of Figure 3b suggests the presence of multiple spectra, yet only one is displayed. The authors should either correct the description or include all relevant spectra.
2. The manuscript does not justify the selected ratios of the composite film components. A clear explanation for these choices should be provided.
3. The authors should clarify why DMSO and isopropyl alcohol were chosen for film preparation. Are these solvents optimal for dispersion stability, film formation, or other properties?
4. The resolution of the figures, particularly the IR spectra, is insufficient for detailed analysis. Higher-quality images must be provided. The IR spectra vary significantly in intensity, making direct comparison difficult. The authors should either normalize the spectra or reacquire them under consistent conditions.

5. The Materials and Methods section requires expansion to include all relevant experimental parameters for reproducibility. Were the FTIR spectra obtained via ATR or pellet (KBr) method? The experimental conditions (e.g., resolution, scan number) should be detailed.

 

Author Response

Response to the reviewers’ comments

Firstly, we deeply appreciate the reviewers for their hard work on our manuscript. Those comments are all valuable and very helpful for revising and improving our paper, as well as with important guiding significance to our future research. Below you will find our point-by-point response to the reviewers’ comments (Responses are marked in blue, and sentences revised in the manuscript are marked in red):

************************************************************************************************

Reviewers’ comments:

Reviewer #2:

1. Figures 3c and 3d are referenced in the text but are absent from the manuscript. The description of Figure 3b suggests the presence of multiple spectra, yet only one is displayed. The authors should either correct the description or include all relevant spectra.

Response: Thank you for your reminder. We have corrected and made modifications on Figure 3. The revised version is as follows:

“As illustrated in Figure 3a, when the IPA volume ratio  is 10%, the PEDOT:PSS dispersion exhibits uniform morphology, with the highest conductivity (1.21 S/cm) and WCA (132.39°). Nevertheless, when the IPA concentration is excessively high, the film is insufficiently thick and fragile. However, when the volume ratio of IPA is lower than 10%, it will lead to an uneven distribution of PEDOT-rich agglomerates in the system and insufficient conformational optimization of the PEDOT chain, thus resulting in a decrease in electrical conductivity [46]. For example, when the IPA volume ratio was 8%, the conductivity of the composite film decreased to approximately 0.9 S/cm. On the other hand, the addition of DMSO can facilitate the dispersion of the PEDOT chain and reduce the PSS wrapping between PEDOT, thereby improving the conductivity of PEDOT:PSS [47-49]. In this study, we chose to add 5% (v/v) DMSO to achieve the optimal conductivity, which have been widely known in this filed [47]. As both PDMS-PUa and SiO₂ contain Si-O bonds, they can be dispersed in IPA to form a uniform mixture and to prepare blue films. Therefore, in the following experiments, PEDOT:PSS/DMSO (5%)/IPA (10%) will be selected as the object. From the UV-vis absorption spectra, it can be seen that there is a strong absorption peak near 654 nm, which is due to the dioxane group reducing the energy barrier of the polythiophene structure (Figure 3b) [50].”

[46] Abdel-Fattah, T.M.; Younes, E.M.; Namkoong, G.; El-Maghraby, E.M.; Elsayed, A.H.; Abo Elazm, A.H. Solvents effects on the hole transport layer in organic solar cells performance. Sol. Energy, 2016, 137: 337-343.

 

Figure 3. (a) The effect of IPA on the conductivity and WCA of PEDOT:PSS/PDMS-PUa (30 wt.%)/SiO₂ film, with images of (b) UV-vis absorption spectrum. (c) The SEM images of the cross-section of PEDOT:PSS/PDMS-PUa (50 wt.%)/SiO₂ film. (d) The influence of PDMS-PUa (wt.%) on the elemental weight of S on the top surface and cross-section of PEDOT:PSS/PDMS-PUa/SiO₂ films, and (e) its impact on EDS intensity.

2. The manuscript does not justify the selected ratios of the composite film components. A clear explanation for these choices should be provided.

Response: Thank you for your question. Based on your suggestion, on the basis of our previous description, we have made further clarification about the selected ratios of the composite film components, as follows.

Determination of the PDMS-PUa ratio: We primarily took into comprehensive consideration the conductivity and WCA of the composite formed by PDMS-PUa and PEDOT:PSS. When the content of PDMS-PUa is 30 wt.%, WCA of the film reaches its maximum value (132.89°), and it  also exhibits good conductivity. For related information, please refer to “3.3.1. Surface hydrophobicity” section.

Determination of the IPA ratio: When the IPA volume ratio  is 10%, the PEDOT:PSS dispersion exhibits uniform morphology, with the highest conductivity (1.21 S/cm) and WCA (132.39°). When the IPA concentration is higher than 10%, the film is insufficiently thick and fragile. When the volume ratio of IPA is lower than 10%, it will lead to an uneven distribution of PEDOT-rich agglomerates in the system and insufficient conformational optimization of the PEDOT chain, thus resulting in a decrease in electrical conductivity. For example, when the IPA volume ratio was 8%, the conductivity of the composite film decreased to approximately 0.9 S/cm. For related information, please refer to “3.2.1. Color and UV-vis absorption spectra” section.

Determination of the DMSO ratio: As most studies demonstrated, the addition of 5% (v/v) DMSO can maximize the improvement in the electrical conductivity of PEDOT:PSS based film (referring to: https://doi.org/10.1016/j.apsusc.2019.143967, https://doi.org/10.1039/C5TC00276A, etc.).  For related information, please refer to “3.2.1. Color and UV-vis absorption spectra” section.

Determination of SiO₂ ratio: We previously tested the impact of different SiO₂ contents on WCA of PEDOT:PSS based composite film. It was found that when 5 wt.% SiO₂ was added, PEDOT:PSS/PDMS-PUa/SiO₂ film exhibited the highest WCA (128.9°). The relevant data has been included in the following figure, and related content also has been supplemented in the supporting information (Figure S3).

 

Figure S3. The influence of varying SiO₂ contents on the hydrophobic properties of PEDOT:PSS/PDMS-PUa (30 wt.%)/SiO₂ composite films. 

Revised “3.3.2. Surface abradability” section:

“In Figure 4h, the WCA of PEDOT:PSS film exhibited hydrophilic properties even under 40 times of friction although showed a decreasing trend (Figure S5). With the incorporation of 30 wt.% PDMS-PUa and 5 wt.% SiO₂ (mainly due to its high WCA, as shown in Figure S3), the friction resistance of PEDOT:PSS/PDMS-PUa/SiO₂ film gradually increased. After undergoing 40 times of friction, its WCA remained at about 100°, maintaining good hydrophobic properties, and further indicating that its good wear resistance.”

3. The authors should clarify why DMSO and isopropyl alcohol were chosen for film preparation. Are these solvents optimal for dispersion stability, film formation, or other properties?

Response: Thank you for your suggestion. IPA and DMSO are the most popular additives for PEDOT:PSS dispersions. On the one hand, adding IPA to the aqueous dispersion of PEDOT:PSS can mitigate the defect of uneven dispersion of PEDOT-rich agglomerates within the system, while also improving the wettability of PEDOT:PSS on the substrate, resulting in a more uniform distribution. On the other hand, the addition of DMSO can facilitate the dispersion of the PEDOT chain and reduce the PSS wrapping between PEDOT, thereby improving the conductivity of PEDOT:PSS. More information can refer to our current review paper “PEDOT:PSS-based Electronic Materials: Preparation, Performance Tuning, Processing, Applications, and Future Prospect. Progress in Polymer Science, 2025, 166, 101990. https://doi.org/10.1016/j.progpolymsci.2025.101990”. The relevant modifications have been added to the “3.2.1. Color and UV-vis absorption spectra” section of the revised manuscript, as follows:

“As illustrated in Figure 3a, when the IPA content is 10%, the PEDOT:PSS dispersion exhibits uniform morphology, with the highest conductivity (1.21 S/cm) and WCA (132.39°). Nevertheless, when the IPA concentration is excessively high, the film is insufficiently thick and fragile. However, when the volume ratio of IPA is lower than 10%, it will lead to an uneven distribution of PEDOT-rich agglomerates in the system and insufficient conformational optimization of the PEDOT chain, thus resulting in a decrease in electrical conductivity[46]. The addition of DMSO can facilitate the dispersion of the PEDOT chain and reduce the PSS wrapping between PEDOT, thereby improving the conductivity of PEDOT:PSS [47-49].”

[46] Abdel-Fattah, T.M.; Younes, E.M.; Namkoong, G.; El-Maghraby, E.M.; Elsayed, A.H.; Abo Elazm, A.H. Solvents effects on the hole transport layer in organic solar cells performance. Sol. Energy, 2016, 137: 337-343.

[47] Mahato, S.; Puigdollers, J.; Voz, C.; Mukhopadhyay, M.; Mukherjee, M.; Hazra, S. Near 5% DMSO is the best: A structural investigation of PEDOT:PSS thin films with strong emphasis on surface and interface for hybrid solar cell. Appl. Surf. Sci, 2020, 499: 143967.

[48] Tounakti, C.; Decorse, P.; Kouki, F.; Philippe, L. Relationship between enhancement of PEDOT: PSS conductivity by solvent treatment and PSS chain reorganization. J. Polym. Sci, 2023, 61(7): 582-603.

[49] Chou, T.R.; Chen, S.H.; Chiang, Y.T.; Lin, Y.T.; Chao, C.Y. Highly conductive PEDOT: PSS films by post-treatment with dimethyl sulfoxide for ITO-free liquid crystal display. J. Mater. Chem. C, 2015, 3(15): 3760-6.

4. The resolution of the figures, particularly the IR spectra, is insufficient for detailed analysis. Higher-quality images must be provided. The IR spectra vary significantly in intensity, making direct comparison difficult. The authors should either normalize the spectra or reacquire them under consistent conditions.

Response: Based on your suggestion, we have made adjustment to the IR spectra. The modified Figure 2a in the revised manuscript is as follows:

 

5. The MaterialsandMethods section requires expansion to include all relevant experimental parameters for reproducibility. Were the FTIR spectra obtained via ATR or pellet (KBr) method? The experimental conditions (e.g., resolution, scan number) should be detailed.

Response: Thank you very much for this reminder. Based on your suggestion, we have supplemented the detailed experimental conditions and sample testing methods related to FTIR, and the revision is as follows:

Section “2.4.2. Spectral absorbency”:

“The molecular structures of PEDOT:PSS/PDMS-PUa/SiO₂ within films were investigated using an fourier transform infrared (FT-IR) spectrometer (ALPHA-II, Bruker, Germany), under resolution (Δν= 0.5 cm⁻¹), with 16 scans, and under ambient conditions of 25 ± 1 °C. The molecular structures of H₂N-PDMS-NH₂, PDMS-PUa, SiO₂, PEDOT:PSS, and PEDOT:PSS/PDMS-PUa/SiO₂ were analyzed by FT-IR spectroscopy (With the exception of H₂N-PDMS-NH₂, which was analyzed via attenuated total reflection (ATR) spectroscopy, others were all tested as potassium bromide (KBr) pellets).”

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The comments are attached.

Comments for author File: Comments.pdf

Author Response

Response to the reviewers’ comments

Firstly, we deeply appreciate the reviewers for their hard work on our manuscript. Those comments are all valuable and very helpful for revising and improving our paper, as well as with important guiding significance to our future research. Below you will find our point-by-point response to the reviewers’ comments (Responses are marked in blue, and sentences revised in the manuscript are marked in red):

************************************************************************************************

Reviewers’ comments:

Reviewer #3:

1. abbreviations. Once defined, use them judiciously to maintain readability. Please revise the following sentence for clarity and grammar: “Herein, we made an endeavor to solve the disadvantages (especially, high moisture absorption, mechanical damage vulnerability, insufficient substrate adhesion ability, etc.) of PEDOT:PSS film by uniformly combining it with polydimethylsiloxane polyurea (PDMS-PUa) and SiO₂ through feasible mechanical stirring, which can organic uses the intermolecular interaction between different components, morphology and structure characteristics.” The sentence is grammatically incorrect and conceptually unclear.

Response: In response to your suggestions, we have checked the abbreviations in the entire text and made modifications to the paragraph you mentioned, and the revisions are as follows:

“In this study, we have made a concerted effort to overcome the inherent drawbacks of PEDOT:PSS film (especially, high moisture absorption, mechanical damage vulnerability, insufficient substrate adhesion ability, etc.) by uniformly blending them with polydimethylsiloxane polyurea (PDMS-PUa) and silica (SiO₂) nanoparticles through a feasible mechanical stirring process, which effectively harnesses the intermolecular interactions as well as the morphological and structural characteristics among the various components.”

2. The overall writing quality of the abstract should be improved for clarity, conciseness, and flow.

Response: Following your recommendation, we have refined the “Abstract” as shown below:

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) stands out as a renowned commercial conducting polymer composite, boasting extensive and promising applications in the realm of film electronics. In this study, we have made a concerted effort to overcome the inherent drawbacks of PEDOT:PSS films (especially, high moisture absorption, mechanical damage vulnerability, insufficient substrate adhesion ability, etc.) by uniformly blending them with polydimethylsiloxane polyurea (PDMS-PUa) and silica (SiO₂) nanoparticles through a feasible mechanical stirring process, which effectively harnesses the intermolecular interactions, as well as the morphological and structural characteristics, among the various components. The Si-O bonds within PDMS-PUa and the -CH₃ groups attached to Si atoms significantly enhance the hydrophobicity of the composite film (as evidenced by a water contact angle of 132.89° under optimized component ratios). Meanwhile, SiO₂ microscopically modifies the surface morphology, resulting in increased surface roughness. This composite film not only maintains high conductivity (1.21 S/cm, in contrast to 0.83 S/cm for the PEDOT:PSS film) but also preserves its hydrophobicity and electrical properties under rigorous conditions, including high-temperature exposure (60-200 °C), ultraviolet (UV) aging (365.0 nm, 1.32 mW/cm²), and abradability testing (2000 CW abrasive paper, drag force of approximately 0.98 N, 40 cycles). Furthermore, the film demonstrates enhanced resistance to both acidic (1 mol/L, 24 h) and alkaline (1 mol/L, 24 h) environments, along with excellent self-cleaning and de-icing capabilities (−6 °C), as well as satisfactory adhesion (Level 2). Notably, the dried composite film can be re-dispersed into a solution with the aid of isopropanol through simple magnetic stirring and the sequentially coated films also exhibit good surface hydrophobicity (136.49°), equivalent to that of the pristine film. This research aims to overcome the intrinsic performance drawbacks of PEDOT:PSS based materials, enabling them to meet the demands of complex application scenarios in the field of organic electronics while endowing them with multifunctionality.

 

3. Remove abbreviations from the abstract. Define all terms in full upon first mention.

Response: Following your comment, we have provided complete definitions for all previously undefined terms that were first mentioned in the full text.

4. Please cite the relevant review article in the sentence: “However, although it can combine the two functions of conductive fillers and polymer matrices into one, as analyzed by our team in the previous review paper.”

Response: Based on your suggestion, we have added reference to the sentence you mentioned.

Section “1. Introduction”:

“However, although it can combine the two functions of conductive fillers and polymer matrices into one, it has serious problems such as high moisture absorption rate, vulnerability to mechanical damage, and insufficient matrix adhesion ability [14].”

[14] Chen, S.; Liang, L.S.; Zhang, Y.Q.; Lin, K.W.; Yang, M.N.; Zhu, L.; Yang, X.M.; Zang, L.; Lu, B.Y. PEDOT: PSS-based electronic materials: Preparation, performance tuning, processing, applications, and future prospect. Prog. Polym. Sci. 2025, 166, 101990.

5. Correct the grammar in this sentence: “It is also usually to modify the surface with fluorine/silicon containing organic compounds, long chain alkanes and other low surface energy substances to reduce the surface free energy.”

Response: Thank you for this reminder. We have revised the sentence you mentioned.

Section “1. Introduction”:

“Surface modification is commonly performed using fluorine/silicon-containing organic compounds, long-chain alkanes, and other low-surface-energy substances to reduce the surface free energy.”

6. Replace hyphens with an dashes (–)for chemical groups like “-SO₃⁻” throughout the manuscript.

Response: Following your recommendation, we have replaced all hyphens with dashes for chemical groups throughout the manuscript, such as “-SO₃⁻”.

7. Please provide supporting references for this sentence: “On the other hand, the PUa component allows for the control of material hardness, toughness, and interactions with other components by adjusting its chemical composition.”

Response: Based on your suggestion, we have added relevant reference in the revised manuscript.

Section “1. Introduction”:

“On the other hand, the PUa component allows for the control of material hardness, toughness, and interactions with other components by adjusting its chemical composition [40]”

[40] Xie, Q.Y.; Liu, C.; Lin X.B.; Ma, C.F.; Zhang, G.Z. Nanodiamond reinforced poly(dimethylsiloxane)-based polyurea with self-healing ability for fouling release coating. ACS Appl. Polym. Mater, 2020, 2(8): 3181-8.

8. Avoid repetitive use of abbreviations. Once defined, use them judiciously to maintain readability.

Response: Based on your suggestion, we have checked all the abbreviations in the article and removed the duplicated abbreviations.

9. The sentence referencing Figures S3a-S3d and sulfur content changes is dense. Consider separating into clearer, simpler observations with direct figure references.

Response: According to your suggestion, we have made modifications about these figures, and incorporated them directly into the Figures 3 of the main text instead in supporting information.

In the revised manuscript:

 

Figure 3. (a) The effect of IPA on the conductivity and WCA of PEDOT:PSS/PDMS-PUa (30 wt.%)/SiO₂ film, with images of (b) UV-vis absorption spectrum. (c) The SEM images of the cross-section of PEDOT:PSS/PDMS-PUa (50 wt.%)/SiO₂ film. (d) The influence of PDMS-PUa (wt.%) on the elemental weight of S on the top surface and cross-section of PEDOT:PSS/PDMS-PUa/SiO₂ films, and (e) its impact on EDS intensity.

10. The statement that the composite film “restricts electron transitions in water” should be revised to a more precise description such as “prevents leakage current” or “maintains electrical insulation.”

Response: Based on your suggestion, we have revised the paragraph you mentioned.

Section “3.2.2. Surface resistance and electrical conductivity”: 

Previous version: When it is placed in bare water, the hydrophobic layer on its surface will hinder the direct contact between water molecules and the interior of itself, thereby restricting the contact between conductive components and electron transitions [46].

Revised version: When immersed in pure water, the hydrophobic coating on its surface acts as a barrier that blocks direct interaction between water molecules and the material’s interior, effectively shielding the conductive components from water exposure. This robust physical separation negates influence of water’s conductivity on the film’s electrical circuitry, thereby preserving its electrical insulation properties [51].

11. Clarify whether WCA measurements were taken from multiple film locations, and how the average and standard deviation were calculated.

Response: Based on your suggestion, we have added relevant explanation in the revised manuscript, as follows:

Section“2.4.4. Surface wettability”:

“After preparing the relevant dispersions, they were cast onto soda-lime glass slides (2 cm × 2 cm). Two samples were prepared for each composition ratio. The films were then vacuum-dried at 60°C for 12 h. The WCA of each film was measured by a contact angle goniometer to determine its surface tension (SDC-100, Dongguan Shengding Precision Instrument Co., Ltd., China) under ambient conditions of 25 ± 1 °C and 50% relative humidity (RH). During testing, each sample was measured at three different positions, and the average value of the test results was calculated along with the standard deviation.”

12. While WCA and conductivity are discussed extensively, are there any trade-offs with transparency, mechanical durability, or environmental stability, especially with the PEDOT:PSS/DMSO/IPA formulation?

Response: Thank you for such very insightful comment. We employed a quite classical composite regulation strategy using IPA and DMSO to optimize the comprehensive performances of PEDOT:PSS films. Their effect on the dispersions or films of PEDOT:PSS separately or in combination all have been earned systematically and detailed investigation in the past decades. Related comprehensive impact on optical, electrical, mechanical, thermal, and others can be found in our current review paper “PEDOT:PSS-based Electronic Materials: Preparation, Performance Tuning, Processing, Applications, and Future Prospect. Progress in Polymer Science, 2025, 166, 101990. https://doi.org/10.1016/j.progpolymsci.2025.101990”.  and in a previously published book “PEDOT-Principles and Applications of an Intrinsically Conductive Polymer, 2011, by Taylor and Francis Group, LLC”.

13. Does the modified film composition affect film-substrate adhesion or interfacial energy? How stable is the film under typical device processing conditions (e.g., thermal cycling, humidity exposure)?

Response: Yes, the film composition adjustment could affect the film-substrate adhesion. As the PDMS-PUa content increased, the adhesion of the composite film gradually increased. The reason for this is that the hydrogen bond in the PDMS-PUa interacts with the glass substrate and improves the adhesion. At the same time, the addition of SiO₂ increases the surface roughness of the composite film, which could provide more physical attachment sites for adhesion, enabling mechanical interlocking. Please refer to the revised section “3.3.3. Interfacial adhesion” for relevant content.

“Figure 4i shows that as the PDMS-PUa content increased, the adhesion of the film gradually increased. The reason for this is that the hydrogen bond in the PDMS-PUa interacts with the glass substrate and improves the adhesion of the film [56]. At the same time, the addition of SiO₂ increases the surface roughness of the composite film, which could provide more physical attachment sites for adhesion, enabling mechanical interlocking at interface. That is to say, during the deposition process, PEDOT:PSS can fill into these rough surface structures, forming an interlocking structure that further enhances adhesion [57]. The PDMS-PUa itself also has good viscoelasticity. Although the low surface energy of PDMS may result in its lower adhesion to other materials, its flexibility helps alleviate stress and prevent the film from peeling due to stress concentration during the adhesion process [43].”

14. Please clarify whether the hydrophobicity observed at 30 wt.% PDMS-PUa remains stable over time, especially under ambient or humid conditions. Has this been monitored?

Response: Thank you for this valuable question. Over an extended exposure period, due to the influence of environmental factors such as temperature and air humidity, the values of WCA of PEDOT:PSS film may change due to its strong hygroscopicity. According to previous observation, the WCA of PEDOT:PSS/PDMS-PUa (30 wt.%)/SiO₂ film exhibits relatively stable WCA value under normal temperature conditions (25 ± 5 ^oC) and humidity environment (RH around 60%-80%) within 24 h. However, over a longer duration, due to the difficulty to control the real-time temperature and humidity, and eliminate the influence of the water droplets that have already been added on the surface of the same test film, it is challenging to monitor these effect in real time and to quantify the extent. Based on your suggestion, maybe in the figure, we or other researchers can solve these issues and construct a reliable method to evaluate this issue.

15. The conductivity trend with increasing PDMS-PUa content (initial drop, then rise at 40–50 wt.%) needs further explanation. Is this effect reproducible? Was any error analysis or statistical validation performed?

Response: Regarding the phenomenon you mentioned, where the electrical conductivity initially decreases and then increases with the rising content of PDMS-PUa as shown in Figure AA, we have observed that it is reproducible. Every data was achieved through parallel experiments. Relevant explanation have been enriched in the revised section of “3.2.2. Surface resistance and electrical conductivity,” as shown below, and corresponding morphological characterization have been presented in the Figure 3c. The main reason for this phenomenon is that PDMS-PUa naturally deposits the lower layer due to its high density. Meanwhile, the proportion of PEDOT:PSS in the upper layer increases accordingly, resulting in an enhancement of the film’s conductivity.

 

Figure 3c. The SEM images of the cross-section of PEDOT:PSS/PDMS-PUa (50 wt.%)/SiO₂ film.

16. Regarding the statement: “However, during the preparation of PEDOT:PSS composite films, the addition of DMSO stretches the PEDOT chain and removes some of the PSS”. Please provide literature support or experimental justification for this claim.

Response: Based on your suggestion, we have added reference to this sentence.

Section “3.3.1. Surface hydrophobicity”:

“However, during the preparation of PEDOT:PSS composite films, the addition of DMSO stretches the PEDOT chain and removes some of the PSS, thus reducing the film’s water absorption [47,48,55].”

[47] Mahato, S.; Puigdollers, J.; Voz, C.; Mukhopadhyay, M.; Mukherjee, M.; Hazra, S. Near 5% DMSO is the best: A structural investigation of PEDOT: PSS thin films with strong emphasis on surface and interface for hybrid solar cell. Appl. Surf. Sci, 2020, 499: 143967

[48] Tounakti, C.; Decorse, P.; Kouki, F.; Philippe, L. Relationship between enhancement of PEDOT: PSS conductivity by solvent treatment and PSS chain reorganization. J. Polym. Sci, 2023, 61(7): 582-603.

[48] Shi, H.; Liu, C.; Jiang, Q.; Xu, J. Effective approaches to improve the electrical conductivity of PEDOT: PSS: A review. Adv. Electron. Mater. 2015, 1, 1500017.

17. Clarify how the "40 friction cycles" were performed. Were specific standards, loads, or abrasion methods followed?

Response: This method is followed a reported way in the literature (ref. [42] in the “References” section; https://doi.org/10.1016/j.jallcom.2020.153702). For details, please refer to the section of “2.4.5. Surface abradability”.

“The mechanical stability of hydrophobic film was evaluated by a previously reported method [42]. The surface to be worn was formed from 2000 CW abrasive paper. The sample is subjected to a drag force equivalent to the weight of a 100 g object (approximately 0.98 N), resulting in a linear displacement of 20 cm per cycle. Following every 5 wear test, the WCA on the film surface was quantified.”

18. You mention that the WCA remained “about 100°” after wear. Please include the initial and final WCA values, and the percentage degradation to quantify the effect.

Response: Thank you for this suggestion. We have supplemented the WCA data before and after abrasion.

Section “After undergoing 40 times of friction”:

“After undergoing 40 times of friction, WCA remained at about 100° with a reduction percentage of 24.7% comparing to the initial value of 132.89°, maintaining good hydrophobic properties, indicating that the film had some wear resistance.”

19. The claim that hydrogen bonding improves adhesion is made in the adhesion section. However, no FTIR, XPS, or other spectroscopic evidence is provided to support this interaction. If it cannot be confirmed experimentally, the claim and possibly the related section should be revised or removed.

Response: Thank you for your reminder. Hydrogen bonding exists in the molecular structure of PDMS-PUa, primarily arising from interactions between the ureido groups (NH-CO-NH) in the polyurea segments and the carbonyl groups (C=O) or amino groups (N-H) of adjacent molecular chains. These hydrogen bonding in PDMS-PUa indeed significantly enhances its adhesion to substrates. However, as you mentioned, it is difficult to evaluate experimentally. In this regard, I have supplemented the missing references and made some modification on representation in the revised section of “3.3.3. Interfacial Adhesion”, as shown below.

“Figure 4i shows that as the PDMS-PUa content increased, the adhesion of the film gradually increased. The reason for this is that there are abundant hydrogen bonding existing in the molecular structure of PDMS-PUa, primarily arising from interactions between the ureido groups (NH-CO-NH) in the PU segments and the carbonyl groups (C=O) or amino groups (N-H) of adjacent molecular chains. These hydrogen bonds can interact with the glass substrate to improve the adhesion of the film [56]. At the same time, the addition of SiO₂ increases the surface roughness of the composite film. The rough surface provides more physical attachment sites for other materials, enabling mechanical interlocking. During the deposition process, PEDOT:PSS can fill into these rough surface structures, forming an interlocking structure that further enhances adhesion [57].”

[56] Wang, D.; Yang, K.; Cheng, S. Harsh environment resistible and recyclable thermoplastic polyurea adhesivebased on stable and density hydrogen bonds. Chem. Eng. J, 2024, 482: 148663.

[57] Liu, C, Xie, Q.Y.; Ma, C.F.; Zhang, G.Z. Fouling release property of polydimethylsiloxane-based polyurea with improved adhesion to substrate. IEC Res., 2016, 55(23): 6671-6676.

20. The explanation of thermal effects on conductivity (due to bound water removal and polymer rearrangement) is plausible. However, could the authors support this with TGA, DSC, or other thermal analysis data to confirm such transitions and correlate them with conductivity changes?

Response: Thank you for this valuable comment. Elevated temperatures can induce a structural rearrangement of the PEDOT:PSS film, accompanied by a reorganization of PEDOT chains. This process shrinks the PSS-rich domains and subsequently enhances electrical conductivity. Relevant studies have been previously reported, and we have supplemented the corresponding references based on your suggestion.

Section“3.4.1. Thermostability”:

In order to ascertain the impact of PEDOT:PSS/PDMS-PUa/SiO₂ film under extreme conditions, it  was subjected to different temperatures (60-200 °C) within two hours, during which time the change in the values of WCA and conductivity was being monitored (Figure 5a). With the change in temperature originating at 60 °C, the WCA of PEDOT:PSS/PDMS-PUa/SiO₂ film first decreases from 119.7° to 94.5°, then increases at 120 °C, and then changes slightly. In comparison, the WCA of PEDOT:PSS film  exhibits a downward trend that is relatively stable. For the reason, as the temperature increases, the molecular chain movement of PDMS-PUa intensifies, which may result in an enlargement of the gaps between molecular chains of PEDOT:PSS/PDMS-PUa/SiO₂, thereby affecting the hydrophobicity of the film to a certain extent. Furthermore, an elevation in temperature may lead to the formation of micropores or cracks within the film, affecting its surface roughness and hydrophobicity [43]. As the temperature rises, the overall conductivity of the PEDOT:PSS film shows a decreasing trend, whereas the conductivity of the PEDOT:PSS/PDMS-PUa /SiO₂ composite film exhibits an initial decline followed by a subsequent increase. The elevated temperature can result in a structural rearrangement of the PEDOT:PSS film, accompanied by a rearrangement of PEDOT [58], which shrinks the PSS region and increases conductivity (1.63 S/cm).

[58] Vitoratos, E.; Sakkopoulos, S.; Dalas, E.; Paliatsas, N.; Karageorgopoulos, D. Thermal degradation mechanisms of PEDOT: PSS. Org. Electron, 2009, 10(1): 61-66.

21. The claim that the films offer anti-UV aging capability is not convincingly demonstrated in the presented results. If such data is absent, the heading or claims should be adjusted to reflect the actual scope.

Response: Thank you for this notice. The PEDOT:PSS/PDMS-PUa/SiO₂ film indeed only has a certain degree of UV resistance and does not have enough anti-UV ability outdoor. Therefore, the “Title” has been revised to be more accurate.

Before modification: “Hydrophobic, durable, and reprocessable PEDOT:PSS/PDMS-PUa/SiO₂ film with conductive, self-cleaning, de-icing and UV ageing resistance functionality”.

After modification: “Hydrophobic, durable, and reprocessable PEDOT: PSS/PDMS-PUa/SiO₂ film with conductive, self-cleaning and de-icing functionality”.

22. The explanation includes the formation of silicates from SiO₂ reacting with OH⁻. Was there any direct evidence provided (e.g., FTIR shifts, XRD peaks, SEM-EDS mapping) to support silicate formation and link it to flexibility enhancement?

Response: Thank you for this question. In this study, after the PEDOT:PSS/PDMS-PUa/SiO₂ film was immersed in KOH for 24 h, it exhibited enhanced flexibility. Based on this observation, we propose that the formation of silicates through the reaction between SiO₂ and OH⁻ may lead to significant dissolution of SiO₂ during immersion. This process facilitates the release of internal stress and the reorganization of molecular chains within the film. Additionally, PDMS inherently possesses excellent elasticity and flexibility, which collectively contribute to the improved macroscopic flexibility and foldability of the film. In response, we have supplemented relevant references, and the revised version is as follows:

Section“3.4.3. Resistance to acid and alkali corrosion”: 

“This may be due to the reaction of the SiO₂ with the OH⁻ to form silicate leading to significant dissolution of SiO₂ during immersion, which could facilitate the release of internal stress and the reorganization of molecular chains within the film and thus reduces its rigidity [62].”

[62] He, S.H.; Chen, J.R.; Lu, Y.; Huang, S.; Feng, K. Enhanced waterproof performance of superhydrophobic SiO2/PDMS coating. Prog. Org. Coat, 2024, 197: 108845.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors made required corrections, so manuscript can be accepted.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript is ready for publishing.