# Silicone elastomers with a small MWCNTs content: Thermal properties, surface profile and hydrophobicity

Iryna Sulym, Konrad Terpilowski, Mykola Borysenko, Emmanuel Flahaut, Zarel Valdez-Nava

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Iryna Sulym, Konrad Terpilowski, Mykola Borysenko, Emmanuel Flahaut, Zarel Valdez-Nava. Silicone elastomers with a small MWCNTs content: Thermal properties, surface profile and hydrophobicity. Synthetic Metals, 2026, 317, pp.118090. 10.1016/j.synthmet.2026.118090. hal-05476201

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# Silicone elastomers with a small MWCNTs content: Thermal properties, surface profile and hydrophobicity

Iryna Sulym<sup>a,b,*</sup>, Konrad Terpiłowski<sup>c</sup>, Mykola Borysenko<sup>b,c</sup>, Emmanuel Flahaut<sup>d,e</sup>, Zarel Valdez-Nava<sup>a</sup>

## ARTICLE INFO

### Keywords:

MWCNTs/PDMS nanocomposites
SYLGARD™ 184
Thermal stability
3D surface topology
SEM
Hydrophobicity

## ABSTRACT

MWCNTs/PDMS nanocomposites with a small amount of MWCNTs (0.25, 0.5, 1.5 and 2.5 wt%) were prepared by the solution-casting and curing techniques. The structural properties of the fabricated elastomers were characterized using FTIR and Raman spectroscopies, indicating an interaction between the nanofiller and the polymer through physical bonding. The characteristic peaks of MWCNTs are not visible in the XRD spectra of the obtained polymer nanocomposites due to their lower content and surrounding by the matrix. Thermal decomposition in air was performed to determine the effect of the low-loaded MWCNTs on the thermal-oxidative stability of nanocomposites. Differential thermogravimetric (DTG) analysis showed a notable shift towards higher temperatures at approximately 42 °C, 78 °C, and 33 °C for the first three DTG peaks maxima in the case of the 2.5MWCNTs/PDMS nanocomposite compared to neat PDMS. The morphology and surface roughness were investigated by SEM and a 3D non-contact optical surface profilometer. The incorporation of 2.5 wt% MWCNTs into the PDMS matrix results in an increase in the water contact angle from 95.6 ± 4.2° to 112.4 ± 2.8° and a decrease in the apparent surface free energy from 28.0 ± 3.9 mJ/m² to 20.8 ± 2.4 mJ/m² compared to neat PDMS, demonstrating that the MWCNTs/PDMS nanocomposites are more hydrophobic. Studies were conducted on the stability of surface properties (hydrophobicity, roughness) over time under relevant environmental conditions. This paper shows that the surface topology, wettability and thermal properties of PDMS can be tuned with reasonable confidence using a small amount of MWCNTs.

## 1. Introduction

Polymer nanocomposites – the materials whose polymer matrices include nanosized fillers – are of great interest for various industrial applications [1–5]. The nanoscale structure of additives combined with a unique set of properties such as a very large specific surface area, high surface energy density, electrical and thermal conductivity, superior mechanical strength, heat resistance, and ability to be mixed with other materials to form nanocomposites, created promising opportunities for the development of modern materials and devices [5–8]. Silicone-based elastomers belong to the class of the most promising inorganic synthetic polymers due to their wide-range thermal stability, chemical resistance, low toxicity, elasticity, weatherability. They are extensively used in fields such as electronics, automobiles, aerospace and defense industry

[9–11]. Poly(dimethylsiloxane) (PDMS) includes the [SiO(CH₃)₂] unit and is the most common member of silicone polymers family [9,11,12]. The presence of the Si–O–Si backbone makes PDMS a very flexible material [13]. In addition, PDMS has a low surface free energy, which can be used to fabricate hydrophobic/superhydrophobic surfaces [7, 14–16]. Among all the various carbon-based nanofillers, carbon nanotubes (CNTs) are characterized by excellent intrinsic properties that make them an effective additive component in polymer composites [17]. CNTs possess great flexibility and strength, small mass density, a large aspect ratio (typically >1000) and a hollow geometry [12,18]. In this context, a PDMS matrix filled with multi-walled CNTs (MWCNTs) combines the ease of processing, flexibility and large thermal stability of the polymer with the remarkable electrical, mechanical, and thermal features of MWCNTs [19]. For these reasons, CNTs/PDMS composites

<footnote><sup>a</sup> Univ Toulouse, Toulouse INP, CNRS, LAPLACE, Toulouse, France</footnote>

<footnote><sup>b</sup> Laboratory of Oxide Nanocomposites, Chuiko Institute of Surface Chemistry of NAS of Ukraine, 17 Oleh Mudrak str., Kyiv 03164, Ukraine</footnote>

<footnote><sup>c</sup> Department of Interface Phenomena of Faculty of Chemistry, Maria Curie-Skłodowska University, M. Curie-Skłodowska sq. 3, Lublin 20031, Poland</footnote>

<footnote><sup>d</sup> CIRIMAT, Université de Toulouse, Toulouse INP, CNRS, 118 Route de Narbonne, 31062, Toulouse cedex 9, France</footnote>

<footnote>* Corresponding author at: Univ Toulouse, Toulouse INP, CNRS, LAPLACE, Toulouse, France.
E-mail address: iryna.sulym@laplace.univ-tlse.fr (I. Sulym).</footnote>
<figure><img src="image_3.png" /><figcaption>Fig. 1. Curing mechanism of silicone with the platinum catalyst (there are no by-products generated in this process).</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>Fig. 2. Scheme of the fabrication process of MWCNTs/PDMS nanocomposites.</figcaption></figure>

<table><caption>**Table 1**
The sample details of as-prepared MWCNTs/PDMS nanocomposites.</caption><thead><tr><th>Sample code</th><th>Wt. percentage of P-MWCNTs (wt%)</th><th>MWCNTs (g)</th><th>S184 (Part A) (g)</th><th>S184 (Part B) (g)</th><th>PDMS-10 (g)</th></tr></thead><tbody><tr><td>Neat PDMS</td><td>0.000</td><td>0.000</td><td>4.960</td><td>0.580</td><td>1.080</td></tr><tr><td>0.25MWCNTs/ PDMS</td><td>0.250</td><td>0.011</td><td>3.020</td><td>0.420</td><td>1.040</td></tr><tr><td>0.5MWCNTs/ PDMS</td><td>0.500</td><td>0.030</td><td>4.940</td><td>0.580</td><td>1.080</td></tr><tr><td>1.5MWCNTs/ PDMS</td><td>1.500</td><td>0.073</td><td>3.040</td><td>0.420</td><td>1.040</td></tr><tr><td>2.5MWCNTs/ PDMS</td><td>2.500</td><td>0.113</td><td>3.020</td><td>0.440</td><td>1.060</td></tr></tbody></table>

are used in numerous areas, including biomedical and tissue engineering, membranology, flexible and power nanoelectronics, touch sensors [20–22]. Various techniques to fabricate CNTs/PDMS nanocomposites have been reported in the literature, namely mechanical stirring, in-situ polymerization, shear mixing, solvent mixing, electrospinning, melt blending and exfoliation [12,23]. However, achieving a uniform dispersion of carbon nanotubes in a polymeric material is still a

challenging topic. In recent decades, physical approaches (sonication, manual stirring, shear mixing by bead milling) and chemical treatment of carbon nanotubes have both been used to improve the dispersion of MWCNTs in a silicon matrix [24]. It is known that a homogeneous dispersion of carbon nanotubes in the PDMS matrix and a strong bonding force between each other are still the key to improve the properties of the composite.

The thermal characteristics of the nanocomposite are as important as its mechanical and electrical properties, as this gives more freedom in the choice of the field of application. It was noticed that the addition of MWCNTs into the PDMS matrices leads to an increase in the glass transition as well as, melting and thermal decomposition temperatures [12,25,26]. This phenomenon is mainly interpreted due to the hindered chain and segmental mobility of the polymer materials [27,28].

This paper discusses MWCNTs/PDMS elastomeric nanocomposites fabricated in a range of MWCNTs concentrations (0.25 – 2.5 wt%) using the solution-casting and curing approach. A set of methods, namely: ATR-FTIR, XRD, Raman spectroscopy, SEM and optical surface profilometry were applied to investigate the polymer nanocomposites in terms of structural properties, dispersion and surface topology. Besides, the influence of the surface structure on the hydrophobic features was analyzed by measuring the water contact angle and estimating the
<figure><img src="image_5.png" /><figcaption>Fig. 3. Actual fabricated samples: neat PDMS and MWCNTs/PDMS nanocomposites with different MWCNTs contents.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 4. ATR-FTIR spectra for (1) S184 (pre-polymer, Part A), (2) PDMS-10, (3) neat PDMS and (4) 2.5MWCNTs/PDMS nanocomposite.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig. 5. XRD analysis of neat PDMS (1), 0.25MWCNTs/PDMS (2), 0.5MWCNTs/PDMS (3), 1.5MWCNTs/PDMS (4) and 2.5MWCNTs/PDMS nanocomposites (5).</figcaption></figure>

surface free energy. In addition, after three years of storage of the samples under appropriate environmental conditions, durability studies of surface properties (hydrophobicity, roughness) were conducted. The thermal stability of the neat PDMS and prepared polymer nanocomposites was analyzed using thermogravimetric/differential thermal analysis (TG/DTA) in air atmosphere. Many researchers would like to introduce CNTs into polymer matrix to improve the thermal stability of the resulting materials, but most of them use a large amount of fillers, resulting in the possible degradation of some other properties of the polymer matrix may [27,29,30]. The present study aimed to correlate the surface profile, hydrophobicity, and thermal properties of neat PDMS and MWCNTs/PDMS nanocomposites with the addition of a small content of nanofiller.

## 2. Experimental

### 2.1. Materials

Pristine MWCNTs (P-MWCNTs) were used as a nanofiller (outer diameter in the range of 10–22 nm and the specific surface area of 160 m²/g), obtained by the catalytic chemical vapour deposition method using pyrolysis of propylene on a mixed metal oxides catalyst, detailed in a previous work [31]. The PDMS kit (S184, SYLGARD™ 184 silicone elastomer, Dow Corning, Germany) consisting of pre-polymer resin (Part A, viscosity of 5100 cSt) and curing agent (Part B, viscosity of 110 cSt) was used as a matrix for the development of nanocomposites at the ratio of 10:1. Mixing these components initiates a curing process which is usually aided by heat. Cross-linking occurs between the vinyl-terminated group from part A and the Si–H group from part B in the presence of the Pt-based catalyst (Fig. 1) [32,33]. To improve the dispersion of carbon nanotubes, low viscosity (10 cSt) trimethyl-terminated poly(dimethylsiloxane) (PDMS-10, Sigma-Aldrich, Germany) was added. The PDMS polymer was chosen for its good hydrophobic properties and ease of fabrication. *n*-Hexane (high-performance liquid chromatography HPLC grade with >95 % purity, Alfa Aesar, Kandel, Germany) was used as a non-polar organic solvent common for both PDMS and MWCNTs to enhance the dispersion.

### 2.2. Fabrication of MWCNTs/PDMS nanocomposites

The incorporation of the carbon nanotubes into the polymer matrix was performed using the solution-casting and curing method (Fig. 2). To avoid agglomeration and to promote good dispersion of P-MWCNTs within PDMS, nanocomposites were prepared by combination of mechanical stirring and sonication [34]. First, P-MWCNTs were dispersed in the *n*-hexane solution by ultrasonication treatment for 10 min. Then, the polymer elastomer component of PDMS kit (Part A) was added into the dispersion of MWCNTs in *n*-hexane and further sonicated for 10 min. Subsequently, PDMS-10 was poured into the mixture with further ultrasonication for 5 min. To help the evaporation of the solvent, the MWCNTs/PDMS composite mixtures were heated at 70 °C by means of magnetic stirring (30 min). The resulting product was mixed with a curing agent (Part B) followed by degassing under vacuum to remove any entrapped air bubbles, forming a very viscous slurry. In the final step, the mixtures were poured into molds (30 mm diameter) and cured at 80 °C for 2 h in air. The fabricated MWCNTs/PDMS nanocomposites were prepared at different concentrations such of MWCNTs (0.25, 0.5, 1.5 and 2.5 wt%). The final samples were labelled as xMWCNTs/PDMS, where x represents the MWCNTs content (wt%) in the nanocomposite. Neat (no addition of P-MWCNTs) PDMS (S184 + PDMS-10) matrix was prepared by the same procedure to be used as control. The thickness of the final samples was approximately 1.2 mm.

Table 1 shows details of the various filler concentrations and composition for each MWCNTs/PDMS nanocomposite sample.

Fig. 3 shows the fabricated neat PDMS and polymer nanocomposite discs.
<figure><img src="image_8.png" /><figcaption>**Fig. 6.** Raman spectra of neat PDMS (a), P-MWCNTs (b) and MWCNTs/PDMS nanocomposites (c) with four different MWCNTs contents 0.25 wt% (1), 0.5 wt% (2), 1.5 wt% MWCNTs (3) and 2.5 wt% (4).</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>**Fig. 7.** Relative intensity ratios of the D/G bands for P-MWCNTs and MWCNTs/PDMS nanocomposites.</figcaption></figure>

## 2.3. Characterization of MWCNTs/PDMS nanocomposites

The molecular bonding of neat PDMS and MWCNTs/PDMS nanocomposites was evaluated from the Fourier-transform infrared spectroscopy (ThermoNicolet iS10 FTIR spectrometer) (wavenumber range 4000 $cm^{-1}$ – 400 $cm^{-1}$) using the ATR technique. The spectra were smoothed, baseline aligned and presented as the absorbance ones.

The structural analysis of the samples was performed using the X-ray diffraction (XRD, DRON-3M diffractometer, Burevestnik, St.-Petersburg, Russia) at room temperature with the CuKα radiation ($\lambda$ = 0.15418 nm) and a Ni filter. The measurements were performed in the mode of reflected rays and the Bragg-Brentano geometry. The diffraction angle measurement range was from 5° to 60° with a step of 0.05° (samples

were glued onto the silica substrates using vaseline oil).

The Raman spectra were obtained at $\lambda_0$ = 514 nm in the range of 0 – 3200 $cm^{-1}$ using an inVia Raman Reflex Microscope DMLM Leica Research Grade (Renishaw, UK) for further confirmation of the presence and successful incorporation of MWCNTs in PDMS. The normalization, baseline correction and smoothing functions were used.

The thermogravimetric/differential thermal analysis (TG/DTA) of P-MWCNTs, neat PDMS and MWCNTs/PDMS nanocomposites was performed in air. The TG, DTA and differential TG (DTG) curves were recorded using a Derivatograph Q-1500D (Paulik, Paulik & Erdey, MOM, Budapest) over the 20 – 900 °C range at a heating rate of 10 °C/min. The samples (mass ~ 50 mg) were placed in an alumina crucible. For TG/DTA analysis, aluminum oxide ($\alpha$-Al₂O₃, corundum) was used as a standard.

Scanning electron microscopy (SEM) along with energy-dispersive X-ray spectroscopy (EDX) was used to investigate the dispersion and morphology of the neat PDMS, P-MWCNTs and polymer nanocomposites. The images were taken using a TESCAN VEGA3 (Czech Republic) apparatus with an accelerating voltage of 20 kV. SEM images of the top-view and the fracture surface of the neat PDMS and polymer nanocomposites were obtained. The cross-section of the fracture surface was created by immersing the samples in liquid nitrogen (LN) for about 1–2 min, and then manually breaking them. Since the boiling point of LN (– 197.79 °C) is lower than the glass transition ($T_g$) of PDMS (– 124 °C), the cooled LN samples underwent a brittle fracture along the cross-section. In the brittle fracture, crack propagation is expected to occur through regions of low bond strength and grain boundaries, where MWCNTs can be discerned. The polymer samples were covered with a thin Au/Pd layer (10 nm in thickness) (Q 15OR ES plus) to make them conductive for the surface morphological analysis. After that step the specimens were fixed on the circular aluminum holder with the double-sided adhesive carbon tape. ImageJ 1.54 g, Java 1.8.0_345 [64-bit]
<figure><img src="image_10.png" /><figcaption>**Fig. 8.** TG (a, left) and corresponding DTG (b, right) plots for neat PDMS, MWCNTs/PDMS polymer nanocomposites (a,b) as well as TG/DTG curves for P-MWCNTs (c) in air atmosphere.</figcaption></figure>

<table><caption>**Table 2**
The details of DTG curves.</caption><thead><tr><th rowspan="2">Sample code</th><th colspan="4">Characteristic temperature in air (°C)</th></tr><tr><th>T<sup>1</sup><sub>max</sub></th><th>T<sup>2</sup><sub>max</sub></th><th>T<sup>3</sup><sub>max</sub></th><th>T<sup>4</sup><sub>max</sub></th></tr></thead><tbody><tr><td>Neat PDMS</td><td>348</td><td>438</td><td>507</td><td>-</td></tr><tr><td>P-MWCNTs</td><td>-</td><td>-</td><td>653</td><td>884</td></tr><tr><td>1.5MWCNTs/PDMS</td><td>384</td><td>503</td><td>539</td><td>702</td></tr><tr><td>2.5MWCNTs/PDMS</td><td>390</td><td>515</td><td>540</td><td>702</td></tr></tbody></table>

<figure><img src="image_11.png" /><figcaption>**Fig. 9.** Residue at 900 °C of the materials studied in the air.</figcaption></figure>

software was used to measure a minimum of 100 random diameters of carbon nanotubes obtained from the SEM images. The average diameter of the P-MWCNTs was then analyzed and calculated based on the

collected data.

To obtain information about the topography of the fabricated elastomeric samples, a 3D non-contact optical surface profiler (Contour GT-K13D, Bruker, Germany) was used. This procedure was performed on three different sites of the top surface on each sample, the surfaces in contact with the mold were not analyzed. The sampling area was 940 µm × 1300 µm. The roughness parameters (R<sub>a</sub>, R<sub>q</sub>, R<sub>r</sub>) were calculated using the WYKO – Vision64 (ver.5.41) software.

Advancing (ACA) and receding (RCA) contact angles of water drops put on the surface of polymer discs were obtained using the DigiDrop Contact Angle Meter (GBX, Romans-sur-Isère, France) equipped with a closed and humidity-controlled measuring chamber as well as a digital camera. Measurements were performed as follows: a 6 µL drop of water was settled on the surface of the test sample using an automatic deposition system and the ACA was measured, then 2 µL of the liquid volume was sucked into a syringe and the RCA was estimated. An average of ten measurements was taken to report ACA and RCA values and measurement deviation. The contact angle values were calculated using the WinDrop++ software. Assuming that the ACA is the largest possible on the examined surface and the RCA is the smallest, the equilibrium contact angle (ECA) known from the Young's equation [35] should have a value in between. In this paper, wettability was described using the equilibrium contact angle calculated according to the Tadmor's theory [36].

For determination of the apparent surface free energy (ASFE), a new approach developed by Chibowski (2) [37] was used. This model is based on the contact angle hysteresis (CAH) and can be applied for to all types of surfaces. The surface free energy of solid (Eq. 1) can be calculated from the advancing and receding contact angles of the liquid whose surface tension is known.

$$ \gamma_s^{tot} = \frac{\gamma_L (1 + \cos\theta_a)^2}{(2 + \cos\theta_r + \cos\theta_a)} \quad (1) $$

<footnote>ᵃTmax - the maximum weight loss rate temperature.</footnote>
<figure><img src="image_12.png" /><figcaption>Fig. 10. SEM images of top-view (×500, left) and cross-section view (×20.0 Kx, right) for neat PDMS (a, f); PDMS with 0.25 wt% MWCNTs (b, g); PDMS with 0.5 wt% MWCNTs (c, h); PDMS with 1.5 wt% MWCNTs (d, i) and PDMS with 2.5 wt% MWCNTs (e, j). Red circles indicate what we assume to be MWCNTs agglomerations, and red arrows indicate MWCNTs bundles.</figcaption></figure>

where: γ<sub>tot</sub> – the surface free energy, γ<sub>L</sub> – the liquid surface tension, θ<sub>a</sub>, θ<sub>r</sub> – the advancing and receding contact angles.

When the equilibrium contact angle is used, (Eq. 1) transforms into (Eq. 2).

$$ \gamma_s = \frac{\gamma_1}{2}(1 + \cos\theta) \qquad (2) $$

Studies of the durability of surface properties (hydrophobicity, roughness) of the obtained neat PDMS and MWCNTs/PDMS elastomers over time under relevant environmental conditions were conducted using a 3D non-contact optical surface profiler, as well as water contact angle (WCA) measurements, as detailed above in this paragraph. The samples were stored in closed petri dishes at a temperature of about 20 °C for three years.

## 3. Results and discussion

### 3.1. ATR-FTIR spectroscopy

The ATR-FTIR spectra of the fabricated neat PDMS, 2.5MWCNTs/ PDMS nanocomposite as well as S184 (pre-polymer, Part A), PDMS-10 are presented in Fig. 4. In the FTIR spectra of all the samples, the symmetric and asymmetric peaks of –CH<sub>3</sub> vibrations in PDMS were found at 2968 and 2910 cm<sup>-1</sup>, respectively [11]. The peaks at 1408 cm<sup>-1</sup> and 1259 cm<sup>-1</sup> are attributed to the –CH<sub>3</sub> deformation vibrations [38]. The broad peak in the range from 1000 to 1200 cm<sup>-1</sup> correspond to the symmetric Si–O–Si stretching [38]. Meanwhile, the peak observed at 846 cm<sup>-1</sup> indicates the Si–C band, while the band at 797 cm<sup>-1</sup> is attributed to the rocking peaks for Si(CH<sub>3</sub>)<sub>2</sub> [38]. A comparison of the ATR-FTIR spectra of all samples (Fig. 4) showed that no new absorption peak appeared for the polymer nanocomposite, indicating that the MWCNTs were only physically blended into the polymer matrix. This was also supported by additional analysis using X-ray photoelectron spectroscopy (XPS) (see Fig. S1, Section A, Supporting information).

### 3.2. XRD analysis

The diffractograms of the studied samples are similar, showing two typical humps associated with the semi-crystalline nature of the polysiloxane chains (Fig. 5). The first peak is observed at 2θ ~ 12°, and the second at 22°. From the data presented in Fig. 5, it can be concluded that increasing the MWCNTs content resulted in small changes in the intensity and width of the observed amorphous peaks compared to neat PDMS. The diffraction peaks at 26° (0 0 2 plane) and 45° (1 0 1 plane) ICDD PDF 01–089–8487, corresponding to the graphitic structure of CNTs (spacing between layers) [39], were not identified in the XRD diffractograms of MWCNTs/PDMS nanocomposites. These results indicate that addition of a small amount of carbon nanotubes to the PDMS matrix has a negligible effect on the crystalline characteristics of the resulting polymer nanocomposites, if any. Similar XRD profiles were obtained by other authors [40].

### 3.3. Raman spectra

Raman spectroscopy is an effective and non-destructive technique for high-resolution characterization of carbon (nano)materials and their composites [41]. Raman spectroscopy (Fig. 6) was used to characterise both the individual components (neat PDMS, P-MWCNTs), and their interactions. The Raman spectrum of neat PDMS exhibits several typical peaks of the silicone elastomer. Peaks associated with skeletal C–C bending vibrations and symmetric Si–O–Si stretching were observed at 179 cm<sup>-1</sup> and 493 cm<sup>-1</sup>, respectively (Fig. 6a) [26,42]. A symmetric Si–CH<sub>3</sub> rocking peak at 626 cm<sup>-1</sup> and a symmetric Si–C stretching band at 709 cm<sup>-1</sup> were noticed. The vibrational peaks at 1267 and 1412 cm<sup>-1</sup> usually refer to the symmetric and asymmetric bending of CH<sub>3</sub> groups, respectively [43]. Moreover, strong intensity peaks corresponding to
<figure><img src="image_13.png" /><figcaption>**Fig. 11.** SEM images of P-MWCNTs with different magnification: (a) × 50.0 Kx, (c) × 25.0 Kx, (d) × 10.0 Kx, and (b) distribution of pristine MWCNTs as a function of their diameters.</figcaption></figure>

symmetric and asymmetric –CH₃ stretching vibrations were observed at 2907 and 2969 cm⁻¹ [26,42].

The Raman spectrum of P-MWCNTs (Fig. 6b) exhibits three main bands: G, D, and 2D. The D band (D = disorder) located at 1355 cm⁻¹ originates from structural defects and/or amorphous carbon. The G band (G = graphite) is present at 1595 cm⁻¹ and informs about the degree of order of the graphene structure in the nanotubes [44,45]. A complex third visible 2D band (defined as the D-overtone mode) is observed between ca. 2600 and 3000 cm⁻¹. The presence of the 2D band further indicates the presence of multiple walls, which should be expected for sample of MWCNTs. [46]. In the Raman spectrum of P-MWCNTs, any radial breathing mode (RBM) band located in the range 100–400 cm⁻¹ was not observed, which excludes the presence of single-walled or double-walled CNTs in the sample [47].

For the MWCNTs/PDMS nanocomposites, the D, G and 2D bands, at ca. 1354 cm⁻¹, 1592 cm⁻¹ and 2707 cm⁻¹, respectively, could be clearly seen (Fig. 6c). The main peaks originating from the PDMS matrix were also observed (Fig. 6c). In our case, even at very low nanofiller loading (0.25 – 2.5 wt%), the main bands of MWCNTs (G, D and 2D) could be easily identified in the nanocomposites.

The ratio between the D and G bands is typically used as an indicator of the amount of defects in CNTs and disordered carbon nanostructures in general [48]. A large value of the relative peak area ratio, I<sub>D</sub>/I<sub>G</sub>, generally indicates a large defect density [49]. The I<sub>D</sub>/I<sub>G</sub> ratio increased from 0.87 (P-MWCNTs) to 1.1 (2.5MWCNTs/PDMS) which is related to a higher density of lattice defects due to the introduction of carbon nanotubes into the polymer matrix as shown in Fig. 7. As FTIR did not reveal any chemical binding between PDMS and MWCNTs, this increase in the number of defects in the MWCNTs may be related to some damaging during the mixing procedure [50].

### 3.4. Thermal analysis

Thermogravimetry is a reliable technique that allows to determine the thermal stability and decomposition of polymeric materials over a wide temperature range. This analysis can also predict and estimate the lifetime of materials under varying climatic/service conditions. In the current paper, the thermal analysis was performed in air for a determination of the thermal-oxidative stability of neat PDMS, P-MWCNTs and polymer nanocomposites. The results are shown in Fig. 8.

The thermal-oxidative degradation of linear poly(dimethylsiloxanes) in air is complex and includes two reactions: oxidation occurs in the side organic groups and degradation occurs in the main chains of the PDMS molecule, which leads to the release of carbonyl compounds and formation of crosslinking points of Si-O-Si [51]. As shown in Fig. 8b, there can be observed two degradation stages in the DTG curves for pure PDMS, while three stages of thermal decomposition are observed for the polymer nanocomposites. Regarding the MWCNTs/PDMS samples, the multiple degradation stages can be related to several reactions, including PDMS depolymerization, oxidation of methyl groups, and the oxidative cross-linking reactions in air (Fig. 8a,b). When MWCNTs are incorporated into the PDMS matrix, the third stage was observed in the temperature range of 640 – 810 °C (Fig. 8b) being attributed to the combustion of MWCNTs according to the literature [26]. Thermal degradation of the P-MWCNTs was also performed (Fig. 8c). In air, P-MWCNTs are thermally stable up to 410 °C. Above this temperature, weight loss begins to occur due to oxidation of remaining amorphous carbon and the MWCNTs themselves. As a result, P-MWCNTs were completely burned at approximately 950 °C (Fig. 8c). Thermal stability of the samples was determined in terms of the maximum weight loss rate temperature (T<sub>max</sub>). The details of DTG curves for the selected samples
<figure><img src="image_14.png" /><figcaption>Fig. 12. 3D height maps obtained for neat PDMS (a), 0.25 wt% (b), 0.5 wt% (c), 1.5 wt% (d) and 2.5 wt% (e) MWCNTs/PDMS nanocomposites.</figcaption></figure>

<table><caption>**Table 3**
The average surface roughness values (±s.d.) of the neat PDMS and MWCNTs/ PDMS nanocomposites.</caption><thead><tr><th>Sample</th><th>R<sub>a</sub></th><th>R<sub>q</sub></th><th>R<sub>t</sub></th></tr></thead><tbody><tr><td>Neat PDMS</td><td>81.8 ± 10.5 nm</td><td>109.1 ± 17.4 nm</td><td>1.8 ± 0.6 µm</td></tr><tr><td>0.25MWCNTs/PDMS</td><td>158.2 ± 14.3 nm</td><td>214.8 ± 3.2 nm</td><td>1.9 ± 0.2 µm</td></tr><tr><td>0.5MWCNTs/PDMS</td><td>5.5 ± 1.0 µm</td><td>7.5 ± 0.8 µm</td><td>67.0 ± 4.0 µm</td></tr><tr><td>1.5MWCNTs/PDMS</td><td>7.9 ± 2.9 µm</td><td>9.8 ± 2.8 µm</td><td>100.7 ± 16.1 µm</td></tr><tr><td>2.5MWCNTs/PDMS</td><td>10.1 ± 3.2 µm</td><td>12.6 ± 2.4 µm</td><td>115.6 ± 21.2 µm</td></tr></tbody></table>

<sup>a</sup>R<sub>a</sub> - the arithmetic mean deviation of the profile from the mean line, measured along measuring or elementary section, R<sub>q</sub> - the Root Mean Square deviation standard from the vertical mean value of measurement coordinates, R<sub>t</sub> - the distance between the deepest valley and the highest elevation.

are listed in Table 2. The addition of 2.5 wt% of MWCNTs to the PDMS matrix determines the upshifts of approximately 42 °C, 78 °C, and 33 °C for the first three DTG peaks maxima.

Fig. 9 gives the weight percentage of the residue at 900 °C of the studied samples. The 2.5MWCNTs/PDMS nanocomposite had 6.5 wt% higher values than neat PDMS in air atmosphere. The larger amount of the residue obtained in air after the degradation of polymer nanocomposites may be explained by the combination of formed traces of silica and residual inclusions of particles [52]. The thermal stability of nanocomposites is slightly improved by the presence of a small content of carbon nanotubes, but this effect is still insignificant, which may also confirm the lack of chemical interactions between MWCNTs and PDMS.

### 3.5. Morphological analysis

SEM was used to characterize the agglomeration and dispersion of MWCNTs within the PDMS matrix. The top-view and the cross-section view SEM images of the fabricated samples are presented in Fig. 10. Neat PDMS was imaged to validate that the samples did not contain

voids (Fig. 10a,f). The topography of the neat polymer is featureless, shows a flat and smooth surface, except for surface contamination (Fig. 10a), which demonstrates that the material is in focus in the SEM. Fig. 10b,c shows the top-view SEM images of the 0.25MWCNTs/PDMS and the 0.5MWCNTs/PDMS nanocomposites, respectively, which are also observed at ×500 magnification and are similar to neat PDMS. Fig. 10d,e shows the top-view morphology of MWCNTs/PDMS nanocomposites with higher carbon nanotubes content, indicating a homogeneous dispersion of MWCNTs (marked by red circles) buried in the PDMS matrix. It was observed that for a larger filler content (2.5 wt%), the SEM image presents more MWCNTs agglomerations (Fig. 10e), highlighting the increase in MWCNTs networks in the polymer matrix. Top-view SEM images of the 1.5MWCNTs/PDMS and 2.5MWCNTs/PDMS nanocomposites, respectively, obtained at higher magnification (×2.0 Kx) are presented in Fig. S2 (Section B, Supporting information).

In Fig. 10g-j the cross-section view of the MWCNTs/PDMS nanocomposites indicates brittle failure, although the topography is more heterogeneous than that of neat PDMS (Fig. 10f), due to the incorporation of carbon nanotubes bundles (marked by red arrows). The dark areas in Fig. 10 are polymer-rich and the lighter regions are usually the bundles of MWCNTs [53,54]. As can be seen (Fig. 10g-j), it is obvious that the MWCNTs are homogeneously dispersed in the polymer matrix, and that all the carbon nanotubes are torn at the fracture surface. SEM images of the cross-section view for the 0.25MWCNTs/PDMS, the 0.5MWCNTs/PDMS and 2.5MWCNTs/PDMS nanocomposites, respectively, obtained at lower magnification (×10.0 Kx), are presented in Fig. S3 (Section B, Supporting information). Furthermore, individual MWCNTs can be observed to be pulled from the PDMS matrix at the peaks of the fracture surface (marked by red arrows). The SEM images in Fig. 10 are consistent with the observations for similar CNTs-PDMS systems [53,55]. Fig. 11 shows SEM images (a, c, d) of P-MWCNTs at 1 µm, 2 µm and 5 µm scales combined with diameter distribution (b). The P-MWCNTs have a smooth surface with bundles of tangled tubes and a calculated average diameter of approximately 21 nm.
<figure><img src="image_15.png" /><figcaption>Fig. 13. Water wettability (a), the apparent surface free energy (b) and state of the water droplet on the obtained disc surfaces (c) as a function of MWCNTs content.</figcaption></figure>

<caption>**Table 4**</caption>

Data literature summary of the water contact angles and thermal stability for CNTs/silicone elastomers according to CNTs content.

<table><thead><tr><th>Polymer matrix</th><th>Filler loading (wt%)</th><th>Thermal stability in air (°C)</th><th>Water contact angle (°)</th><th>Ref.</th></tr></thead><tbody><tr><td rowspan="2">PDMS (Sylgard 184)</td><td>MWCNTs (4.28)</td><td>273</td><td>-</td><td rowspan="2">[12]</td></tr><tr><td>MWCNTs (6.0)</td><td>322</td><td>-</td></tr><tr><td rowspan="4">PDMS (Sylgard 184)</td><td>MWCNTs (1.0)</td><td>575</td><td>-</td><td rowspan="4">[61]</td></tr><tr><td>MWCNTs (2.0)</td><td>545</td><td>-</td></tr><tr><td>MWCNTs (3.28)</td><td>536</td><td>-</td></tr><tr><td>MWCNTs (8)</td><td>-</td><td>104</td></tr><tr><td rowspan="4">PDMS</td><td>MWCNTs (1)</td><td>-</td><td>103.10</td><td rowspan="4">[62]</td></tr><tr><td>MWCNTs (2)</td><td>-</td><td>± 1.51</td></tr><tr><td>MWCNTs (4)</td><td>-</td><td>± 2.89</td></tr><tr><td>NH<sub>2</sub>-MWCNTs (2)</td><td>-</td><td>± 4.13</td></tr><tr><td rowspan="4">PDMS (Sylgard 184 +PDMS10)</td><td>MWCNTs (1.5)</td><td>T<sub>max</sub><sup>1</sup> = 384<br>T<sub>max</sub><sup>2</sup> = 503<br>T<sub>max</sub><sup>3</sup> = 539</td><td>103.0 ± 2.6</td><td rowspan="4">Current study</td></tr><tr><td>MWCNTs (2.5)</td><td>T<sub>max</sub><sup>1</sup> = 390<br>T<sub>max</sub><sup>2</sup> = 515<br>T<sub>max</sub><sup>3</sup> = 540</td><td>112.4 ± 2.8</td></tr></tbody></table>

<sup>a</sup>T<sub>max</sub> - the maximum weight loss rate temperature according to DTG curves.

Energy-dispersive X-ray spectroscopy (EDX) mapping spectrum of

0.5MWCNTs/PDMS and 2.5MWCNTs/PDMS nanocomposites indicated the characteristic elemental distribution (C, O and Si) (see Figs. S4-S5, Section B, Supporting information).

### 3.6. Profilometry

The 3D surface images for all samples are shown in Fig. 12. The scale next to the 3D surface images shows the distribution of the greater difference between the shallowest and highest points of the surface. The higher the number on this scale, the higher the surface roughness. The corresponding arithmetic mean roughness (R<sub>a</sub>), root mean square roughness (R<sub>q</sub>), maximum roughness height (R<sub>t</sub>) and standard deviations (s.d.) are listed in Table 3. The linear parameters (R<sub>a</sub>, R<sub>q</sub> and R<sub>t</sub>) are usually used to characterize the nanocomposite surfaces [56]. The roughness parameters depend on several factors, such as filler size and shape, percentage of surface area occupied by filler particles, hardness, and filler-matrix interaction [57]. As follows from Fig. 12, the surface roughness increases with an increase in the concentration of the filler. Among the investigated samples, the smallest surface roughness (R<sub>a</sub>) was observed for neat PDMS (81.8 ± 10.5 nm) (Table 3). Additionally, 2.5MWCNTs/PDMS nanocomposite showed the highest R<sub>a</sub> and R<sub>q</sub> values (10.1 ± 3.2 µm and 12.6 ± 2.4 µm, respectively).

### 3.7. Wettability and apparent surface free energy

The static measurement of the contact angle is an important indicator of the hydrophobic or hydrophilic nature of the surface. The wettability of surfaces can be strongly affected by surface microstructure, roughness and surface free energy [58]. To study the hydrophobic performance of the fabricated samples, the water contact angle (WCA) and the apparent surface free energy of the neat PDMS and MWCNTs/PDMS nanocomposites were characterized (Fig. 13). It is clear
<figure><img src="image_16.png" /><figcaption>**Fig. 14.** Water wettability (a), the apparent surface free energy (b) and state of the water droplet on the obtained disc surfaces (c) as a function of MWCNTs content after three years of storage.</figcaption></figure>

<table><caption>**Table 5**
The average surface roughness values (±s.d.) of the neat PDMS and MWCNTs/ PDMS nanocomposites after three years of storage.</caption><thead><tr><th>Sample</th><th>R<sub>a</sub></th><th>R<sub>q</sub></th><th>R<sub>t</sub></th></tr></thead><tbody><tr><td>Neat PDMS</td><td>87.8 ± 5.9 nm</td><td>117.1 ± 14.9 nm</td><td>3.4 ± 1.8 µm</td></tr><tr><td>0.25MWCNTs/PDMS</td><td>168.9 ± 13.3 nm</td><td>212.54 ± 3.6 nm</td><td>2.09 ± 0.5 µm</td></tr><tr><td>0.5MWCNTs/PDMS</td><td>5.8 ± 1.1 µm</td><td>7.7 ± 1.1 µm</td><td>65.2 ± 3.6 µm</td></tr><tr><td>1.5MWCNTs/PDMS</td><td>9.4 ± 1.9 µm</td><td>11.5 ± 1.5 µm</td><td>109.1 ± 9.1 µm</td></tr><tr><td>2.5MWCNTs/PDMS</td><td>12.1 ± 2.2 µm</td><td>15.7 ± 2.6 µm</td><td>117.6 ± 25.2 µm</td></tr></tbody></table>

ᵃR<sub>a</sub> - the arithmetic mean deviation of the profile from the mean line, measured along measuring or elementary section, R<sub>q</sub> - the Root Mean Square deviation standard from the vertical mean value of measurement coordinates, R<sub>t</sub> - the distance between the deepest valley and the highest elevation.

that the ECA increases slightly from 95.6 ± 4.2–112.4 ± 2.8 ° with the increasing MWCNTs (Fig. 13a). This is due to the fact that the PDMS components were predomination on the disk surfaces regardless of the MWCNTs mass fraction. The addition of a larger amount of nanofiller (1.5 and 2.5 wt%) increased the hydrophobicity of polymer nanocomposites due to a change in the surface roughness. These results are in good agreement with the 3D surface height maps and SEM observations of the studied samples (Paragraphs 3.5–6).

The surface free energy is the main characteristic of polymers and affects their surface properties significantly [59]. Thus, the apparent surface free energy (ASFE) was calculated and the results are displayed in Fig. 13b. The ASFE of neat PDMS is 28.0 ± 3.9 mJ/m², while the ASFE of 2.5MWCNTs/PDMS nanocomposite is reduced to 20.8 ± 2.4 mJ/m². For the nanocomposites, the ASFE values decrease with the increasing weight content of MWCNTs. The calculated ASFE value is a result of surface roughness and chemical composition of the tested samples.

With increasing MWCNTs content in PDMS composites, a decrease in the water contact angle hysteresis is observed, indicating a reduction in

both topographical and chemical heterogeneity of the surface. Despite the significant increase in roughness (R<sub>a</sub> from ~82 nm to >10 µm, see Table 3), surfaces with higher MWCNTs loading become more uniform on the scale relevant to droplet interaction, as the carbon nanotubes are more evenly distributed and embedded in the polymer matrix, which reduces the number of pinning sites for the droplet (Paragraphs 3.5–6). XPS (see SI section) and FTIR (Paragraph 3.1) analyses confirm that MWCNTs do not introduce new chemical groups – the surface remains chemically dominated by PDMS, and the surface energy variations are smaller than in neat PDMS, which also contributes to the reduction of hysteresis. As a result, the lower hysteresis reflects a more homogeneous, less pinning-prone surface, which is consistent with literature data and typical wetting mechanisms of MWCNTs/PDMS composites [34,60].

As a result, the data obtained in this study are compatible with the literature, and the addition of a small amount of MWCNTs affects the thermo-oxidative stability and wettability of the resulting silicone-based materials (Table 4).

### 3.8. The durability of surface properties (hydrophobicity, roughness)

Recent measurements of water contact angle (WCA) and apparent surface free energy (ASFE) confirmed the hydrophobic nature of all investigated silicone-based elastomer surfaces. Compared to the results obtained three years ago, the current samples exhibited slightly lower ECA (ranging from 99.8 ± 1.3° for neat PDMS to 104.8 ± 0.7° for 2.5 wt % MWCNTs) and correspondingly higher ASFE values (from 30.2 ± 0.7–27.1 ± 0.4 mJ/m², respectively) (Fig. 14). This indicates a modest decrease in surface hydrophobicity, which may be due to partial surface oxidation and aging effects of PDMS over time. Nevertheless, the general trend remains consistent with the previous investigation – an increase in WCA and a decrease in ASFE with increasing MWCNTs
content, confirming that the incorporation of carbon nanotubes en-
hances the hydrophobic character of the nanocomposites, mainly due to
changes in surface roughness and morphology.

After three years of storage under ambient conditions, noticeable
changes were observed in the surface characteristics of the studied
MWCNTs/PDMS nanocomposites. The average roughness parameters
(R<sub>a</sub>, R<sub>q</sub>, R<sub>θ</sub>) increased for all samples compared to the freshly prepared
materials (Table 5), indicating progressive surface oxidation and
degradation of the outer polymer layer. Such oxidation processes likely
lead to the formation of polar silanol (Si–OH) groups and partial chain
scission within the silicone matrix, resulting in a more heterogeneous
and rougher surface texture. At the same time, the WCA values
decreased (Fig. 14), confirming the gradual reduction in surface hy-
drophobicity. The simultaneous increase in surface roughness and
decrease in wettability indicates that the surface follows the Wenzel
wetting model [58], where liquid penetration into surface asperities
enhances the apparent contact angle hysteresis. These effects point
long-term oxidative aging of silicone-based elastomers, which alters
their surface energy balance and may affect their functional perfor-
mance in applications requiring stable hydrophobic behavior.

4. Conclusions

Herein, the fabrication of PDMS-based elastomeric nanocomposites is demonstrated by incorporating small concentrations of MWCNTs (0.25, 0.5, 1.5 and 2.5 wt%) using the solution mixing and curing approaches. The presence of MWCNTs in the PDMS matrix was confirmed by the Raman spectroscopy. The XRD results showed that the microstructure of the polymer nanocomposites was amorphous and that the addition of the carbon nanotubes did not change mainly the bulk properties of the base polymer. The thermal-oxidative stability of PDMS before and after the incorporation of MWCNTs was studied using the thermogravimetric analysis. The temperature of the maximum degradation rate for the 2.5MWCNTs/PDMS nanocomposite in air shifts toward a higher temperature in accordance with the DTG peaks at approximately 42 °C, 78 °C, and 33 °C compared to neat PDMS. The SEM images of neat PDMS indicated that the material did not contain voids. The MWCNTs/PDMS samples with 1.5 wt% and 2.5 wt% MWCNTs contents showed a near-uniformity of top- and fracture surfaces. The overall features of the fractured surfaces seem to be equivalent, i.e. the nanofiller is embedded in the polymer matrix. The population of MWCNTs fragments increase with the increasing MWCNTs loading. The 3D surface maps of the samples exhibit different levels of surface roughness and their profiles. Among the studied samples, the lowest surface roughness (R<sub>a</sub>) was observed for pure PDMS (81.8 ± 10.5 nm), while the highest R<sub>a</sub> and R<sub>q</sub> values (10.1 ± 3.2 µm and 12.6 ± 2.4 µm, respectively) were observed for the 2.5MWCNTs/PDMS nanocomposite. The water contact angle indicates that the prepared polymer nanocomposites are hydrophobic. Due to the addition of carbon nanotubes, the WCA increases and the ASFE decreases for the resulting MWCNTs/PDMS nanomaterials. Furthermore, after three years of storage of samples under ambient conditions, durability studies of surface properties (hydrophobicity, roughness) confirmed that their remained hydrophobic. For the 2.5 MWCNTs/PDMS nanocomposite, the ECA value slightly decreased by 7.1 %, while the ASFE increased by 30.2 % compared to the freshly prepared sample. The overall findings reported in this paper will be helpful for researchers to configure S184 silicone elastomer with multi-walled carbon nanotubes. Further studies on the electrical properties of MWCNTs/PDMS nanocomposites and bulk morphology will be interesting for future developments.

CRediT authorship contribution statement

**Mykola Borysenko:** Writing – review & editing, Resources, Investigation.
**Konrad Terpilowski:** Writing – review & editing, Resources, Formal analysis, Data curation.
**Iryna Sulym:** Writing – original draft,

Validation, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. **Zarel Valdez-Nava:** Writing – review & editing, Resources. **Emmanuel Flahaut:** Writing – review & editing, Resources.

**Declaration of Competing Interest**

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The current paper is funded by the French National Research Agency under the project CARBO2DERM (grants ANR-19-CE09-0007 and ANR-23-PAUK-0080). The authors would like to express their gratitude to Dr. Y.I. Sementsov (CISC, NASU, Kyiv, Ukraine) for providing the pristine MWCNTs as well as to master's student H. Luis (Univ Toulouse, Toulouse INP, CNRS, LAPLACE, Toulouse, France) for the assistance with SEM examination.

**Appendix A. Supporting information**

Supplementary data associated with this article can be found in the online version at doi:10.1016/j.synthmet.2026.118090.

Data Availability

Data will be made available on request.

**References**

[1] S. Bianco, P. Ferrario, M. Quaglio, R. Castagna, C.F. Pirri, S. Bianco, P. Ferrario, M. Quaglio, R. Castagna, C.F. Pirri, Nanocomposites based on elastomeric matrix filled with carbon nanotubes for biological applications, in: Carbon Nanotubes - From Research to Applications, IntechOpen, 2011, https://doi.org/10.5772/18638.

[2] A. Dhillon, D. Kumar, 2 - Recent advances and perspectives in polymer-based nanomaterials for Cr(VI) removal, in: C.M. Hussain, A.K. Mishra (Eds.), New Polymer Nanocomposites for Environmental Remediation, Elsevier, 2018, pp. 29–46, https://doi.org/10.1016/B978-0-12-811033-1.00002-0.

[3] A. Liu, Z. Ni, J. Chen, Y. Huang, Highly sensitive graphene/polydimethylsiloxane composite films near the threshold concentration with biaxial stretching, Polymers 12 (2020) 71, https://doi.org/10.3390/polym12010071.

[4] S. He, Y. Zhang, J. Gao, A. Nag, A. Rahaman, Integration of different graphene nanostructures with PDMS to form wearable sensors, Nanomaterials 12 (2022) 950, https://doi.org/10.3390/nano12060950.

[5] M.R. Vagos, M. Gomes, J.M.R. Moreira, O.S.G.P. Soares, M.F.R. Pereira, F. J. Mergulhão, Carbon nanotube/poly(dimethylsiloxane) composite materials to reduce bacterial adhesion, Antibiotics 9 (2020) 434, https://doi.org/10.3390/antibiotics9080434.

[6] Z. Spitalsky, D. Tasis, K. Papagelis, C. Galiotis, Carbon nanotube–polymer composites: chemistry, processing, mechanical and electrical properties, Prog. Polym. Sci. 35 (2010) 357–401, https://doi.org/10.1016/j.progpolymsci.2009.09.003.

[7] A. Ribeiro, B. Soares, J. Furtado, A. Silva, N. Couto, Superhydrophobic nanocomposite coatings based on different polysiloxane matrices designed for electrical insulators, Prog. Org. Coat. 168 (2022) 106867, https://doi.org/10.1016/j.porgcoat.2022.106867.

[8] P.H.C. Camargo, K.G. Satyanarayana, F. Wypych, Nanocomposites: synthesis, structure, properties and new application opportunities, Mat. Res. 12 (2009) 1–39, https://doi.org/10.1590/S1516-14392009000100002.

[9] P. Lucas, J.-J. Robin, Silicone-Based Polymer Blends: An Overview of the Materials and Processes, in: X. Dong Liu, A.R. Esker, M. Häußler, C. Kim, P. Lucas, M. Matsunaga, N. Nishi, J.-J. Robin, B.Z. Tang, D.-A. Wang, M. Yamada, H. Yu (Eds.), Functional Materials and Biomaterials, Springer, Berlin, Heidelberg, 2007, pp. 111–147, https://doi.org/10.1007/12_2007_115.

[10] J. Kong, Y. Tong, J. Sun, Y. Wei, W. Thitsartarn, C.C.Y. Jayven, J.K. Muiruri, S. Y. Wong, C. He, Electrically conductive PDMS-grafted CNTs-reinforced silicone elastomer, Compos. Sci. Technol. 159 (2018) 208–215, https://doi.org/10.1016/j.compscitech.2018.02.018.

[11] M. Salahchini Javanmardi, E. Ameri, Pervaporation characteristics of PDMS/PMHS nanocomposite membranes inclusive multi-walled carbon nanotubes for improvement of acetic acid–methanol esterification reaction, Polym. Bull. 77 (2020) 2591–2609, https://doi.org/10.1007/s00289-019-02875-z.

[12] N. Sankar, M.N. Reddy, R.K. Prasad, Carbon nanotubes dispersed polymer nanocomposites: mechanical, electrical, thermal properties and surface
morphology. Bull. Mater. Sci. 39 (2016) 47–55, https://doi.org/10.1007/s12034-015-1117-3.

[13] B. Borah, G. Rajitha, R.K. Dash, Correlation between the thickness and properties of the ethanol treated GO-PDMS based composite materials, J. Mater. Sci. Mater. Electron 29 (2016) 2021–2024, https://doi.org/10.1007/s10854-018-0154-2.

[14] M. Jin, X. Feng, J. Xi, J. Zhai, K. Cho, L. Feng, L. Jiang, Super-hydrophobic PDMS surface with ultra-low adhesive force, Macromol. Rapid Commun. 26 (2005) 1805–1809, https://doi.org/10.1002/marc.200500458.

[15] H.-F. Zhang, M.K. Teo, C. Yang, Superhydrophobic carbon nanotube/polydimethylsiloxane composite coatings, Mater. Sci. Technol. 31 (2015) 1745–1748, https://doi.org/10.1179/1743284714Y.00000000752.

[16] Y. Xue, P. Verdross, W. Liang, R.T. Woodward, A. Bismarck, Breaking the ice: applications of photothermal superhydrophobic materials for efficient deicing strategies, Adv. Colloid Interface Sci. 341 (2025) 103489, https://doi.org/10.1016/j.cis.2025.103489.

[17] K.I. Winey, T. Kashiwagi, M. Mu, Improving electrical conductivity and thermal properties of polymers by the addition of carbon nanotubes as fillers, MRS Bull. 32 (2007) 348–353, https://doi.org/10.1557/mrs.2007.234.

[18] Z. Spitalsky, D. Tasis, K. Papagelis, C. Galiotis, Carbon nanotube–polymer composites: chemistry, processing, mechanical and electrical properties, Prog. Polym. Sci. 35 (2010) 357–401, https://doi.org/10.1016/j.progpolymsci.2009.09.003.

[19] B. Mensah, H.G. Kim, J.-H. Lee, S. Arepalli, C. Nah, Carbon nanotube-reinforced elastomeric nanocomposites: a review, Int. J. Smart Nano Mater. 6 (2015) 211–238, https://doi.org/10.1080/19475411.2015.1121632.

[20] N. Sheshkar, G. Verma, C. Pandey, A.K. Sharma, A. Gupta, Enhanced thermal and mechanical properties of hydrophobic graphite-embedded polydimethylsiloxane composite, J. Polym. Res. 28 (2021), https://doi.org/10.1007/s10965-021-02774-w.

[21] M.N. Nejad, M. Asghari, M. Afsari, Investigation of carbon nanotubes in mixed matrix membranes for gas separation: a review, ChemBioEng Rev. 3 (2016) 276–298, https://doi.org/10.1002/cben.201600012.

[22] J. Hong, J. Lee, D. Jung, S.E. Shim, Thermal and electrical conduction behavior of alumina and multiwalled carbon nanotube incorporated poly(dimethyl siloxane), Thermochim. Acta 512 (2011) 34–39, https://doi.org/10.1016/j.tca.2010.08.019.

[23] S. Azhari, A. Termeh Yousefi, H. Tanaka, A. Khajeh, N. Kuredemus, M. Mansouri Bigdeli, M.N. Hamidon, Fabrication of piezoresistive based pressure sensor via purified and functionalized CNTs/PDMS nanocomposite: toward development of haptic sensors, Sens. Actuators A Phys. 266 (2017) 158–165, https://doi.org/10.1016/j.sna.2017.09.026.

[24] Y. Liu, W. Chi, H. Duan, H. Zou, D. Yue, L. Zhang, Property improvement of room temperature vulcanized silicone elastomer by surface-modified multi-walled carbon nanotube inclusion, J. Alloy. Compd. 657 (2016) 472–477, https://doi.org/10.1016/j.jallcom.2015.10.129.

[25] S. Sagar, N. Iqbal, A. Maqsood, M. Shahid, N.A. Shah, T. Jamil, M.I. Bassyouni, Fabrication and thermal characteristics of functionalized carbon nanotubes impregnated polydimethylsiloxane nanocomposites, J. Compos. Mater. 49 (2015) 995–1006, https://doi.org/10.1177/0021998314528733.

[26] E.A. da Silva, G. Windmøller, G.G. Silva, K.C. de S. Figueiredo, Polydimethylsiloxane membranes containing multi-walled carbon nanotubes for gas separation, Mat. Res. 20 (2017) 1454–1460, https://doi.org/10.1590/1980-5373-MR-2016-0825.

[27] T. Shimizu, R. Kishi, K. Kobashi, T. Morimoto, T. Okazaki, T. Yamada, K. Hata, Improved thermal stability of silicone rubber nanocomposites with low filler content, achieved by well-dispersed carbon nanotubes, Compos. Commun. 22 (2020) 100482, https://doi.org/10.1016/j.coco.2020.100482.

[28] P. Klonos, I.Y. Sulym, D. Sternik, P. Konstantinou, O.V. Goncharuk, A. Derylo–Marczewska, V.M. Gun'ko, A. Kyritsis, P. Pissis, Morphology, crystallization and rigid amorphous fraction in PDMS adsorbed onto carbon nanotubes and graphite, Polymer 139 (2018) 130–144, https://doi.org/10.1016/j.polym.2018.02.020.

[29] J.S. Hong, C. Kim, Dispersion of multi-walled carbon nanotubes in PDMS/PB blend, Rheol. Acta 50 (2011) 955–964, https://doi.org/10.1007/s00397-011-0581-y.

[30] L. Bokobza, Enhanced electrical and mechanical properties of multiwall carbon nanotube rubber composites, Polym. Adv. Technol. 23 (2012) 1543–1549, https://doi.org/10.1002/pat.3027.

[31] M. Kartel, Y. Sementsov, S. Mahno, V. Trachevskiy, W. Bo, Polymer composites filled with multiwall carbon nanotubes, Univers. J. Mater. Sci. 4 (2016) 23–31, https://doi.org/10.13189/ujms.2016.040202.

[32] N.S. Gupta, K.-S. Lee, A. Labouriau, Tuning thermal and mechanical properties of polydimethylsiloxane with carbon fibers, Polymers 13 (2021) 1141, https://doi.org/10.3390/polym13071141.

[33] B.S. Snorradóttir, P.I. Gudnason, R. Scheving, F. Thorsteinsson, M. Másson, Release of anti-inflammatory drugs from a silicone elastomer matrix system, Die Pharm. Int. J. Pharm. Sci. 64 (2009) 19–25, https://doi.org/10.1691/ph.2008.8206.

[34] J.H. Kim, J.-Y. Hwang, H.R. Hwang, H.S. Kim, J.H. Lee, J.-W. Seo, U.S. Shin, S.-H. Lee, Simple and cost-effective method of highly conductive and elastic carbon nanotube/polydimethylsiloxane composite for wearable electronics, Sci. Rep. 8 (2018) 1375, https://doi.org/10.1038/s41598-017-18209-w.

[35] L. Makkonen, Young's equation revisited, J. Phys. Condens. Matter 28 (2016) 135001, https://doi.org/10.1088/0953-8984/28/13/135001.

[36] R. Tadmor, Line energy and the relation between advancing, receding, and young contact angles, Langmuir 20 (2004) 7659–7664, https://doi.org/10.1021/la049410h.

[37] K. Terpiłowski, L. Holysz, M. Chodkowski, D. Clemente Guinarte, What can you learn about apparent surface free energy from the hysteresis approach? Colloids Interfaces 5 (2021) 4, https://doi.org/10.3390/colloids5010004.

[38] N.A.S. Salman, M.S.M. Saheed, N.U. Saqib, A.F.A. Latip, R. Adnan, Polydimethylsiloxane-carbon nanotubes-based hydrophobic sponge for treatment of palm oil mill effluents with enhanced reusability, J. Environ. Chem. Eng. 11 (2023) 111019, https://doi.org/10.1016/j.jece.2023.111019.

[39] S.J. Paul, S. Srivastava, J.S. Tawale, B.K. Gupta, Three-dimensional CNT-rGO/PDMS porous scaffold derived supercompressible lightweight body-mounted piezoresistive force sensor for human motion monitoring, Colloids Surf. A Physicochem. Eng. Asp. 675 (2023) 131993, https://doi.org/10.1016/j.colsurf2023.131993.

[40] P. Ferreira, Á. Carvalho, T.R. Correia, B.P. Antunes, I.J. Correia, P. Alves, Functionalization of polydimethylsiloxane membranes to be used in the production of voice prostheses, Sci. Technol. Adv. Mater. 14 (2013) 055006, https://doi.org/10.1088/1468-6996/14/5/055006.

[41] Z. Li, L. Deng, I.A. Kinloch, R.J. Young, Raman spectroscopy of carbon materials and their composites: Graphene, nanotubes and fibres, Prog. Mater. Sci. 135 (2023) 101089, https://doi.org/10.1016/j.pmatsci.2023.101089.

[42] L. Bokobza, J.-L. Bruneel, M. Couzi, Raman spectra of carbon-based materials (from graphite to carbon black) and of some silicone composites, C1 (2015) 77–94, https://doi.org/10.3390/c1010077.

[43] S.C. Bae, H. Lee, Z. Lin, S. Granick, Chemical imaging in a surface forces apparatus: confocal raman spectroscopy of confined poly(dimethylsiloxane), Langmuir 21 (2005) 5685–5688, https://doi.org/10.1021/la050233+.

[44] M. Massaro, S. Riela, G. Cavallaro, M.L. Saladino, S. Agnello, R. Noto, Properties and structural studies of multi-wall carbon nanotubes-phosphate ester hybrids, Int. J. Org. Chem. 3 (2013) 26–34, https://doi.org/10.4236/ijoc.2013.31A003.

[45] A.D. Dobrzańska-Danikiewicz, W. Wolany, D. Łukowiec, K. Jurkiewicz, P. Niedzialkowski, Characteristics of multiwalled carbon nanotubes-rhenium nanocomposites with varied rhenium mass fractions, Nanomater. Nanotechnol. 7 (2017) 184798041770173, https://doi.org/10.1177/1847980417701773.

[46] J. Penaranda-Armbrecht, M.J. Correa-Quiceno, J.C. Caicedo-Angulo, P.A. Neuta-Arciniegas, J.O. Gutiérrez-Montes, Fabrication of multi-walled carbon nanotube/polycaprolactone scaffolds for possible application in tissue engineering, J. Polym. Res 31 (2024) 64, https://doi.org/10.1007/s10965-024-03875-y.

[47] X. Zhao, Y. Ando, L.-C. Qin, H. Kataura, Y. Maniwa, R. Saito, Radial breathing modes of multiwalled carbon nanotubes, Chem. Phys. Lett. 361 (2002) 169–174, https://doi.org/10.1016/S0009-2614(02)00955-7.

[48] S. Costa, E. Borowiak-Palen, M. Kruszynska, A. Bachmatiuk, R.J. Kaleńczuk, Characterization of carbon nanotubes by Raman spectroscopy, Mater. Sci. Pol. 26 (2008), https://yadda.icm.ac.pl/yadda/element/bwmeta1/element.baztec-h-article-PBW7-0007-0213) (accessed November 5, 2024).

[49] Z. Li, L. Deng, I.A. Kinloch, R.J. Young, Raman spectroscopy of carbon materials and their composites: graphene, nanotubes and fibres, Prog. Mater. Sci. 135 (2023) 101089, https://doi.org/10.1016/j.pmatsci.2023.101089.

[50] M. Nour, K. Berean, S. Balendran, J.Z. Ou, J. Du Plessis, C. McSweeney, M. Bhaskaran, S. Sriram, K. Kalantar-zadeh, CNT/PDMS composite membranes for H2 and CH4 gas separation, Int. J. Hydrogen Energy 38 (2013) 10494–10501, https://doi.org/10.1016/j.ijhydene.2013.05.162.

[51] G. Camino, S.M. Lomakin, M. Lazzari, Polydimethylsiloxane thermal degradation Part 1. Kinetic aspects, Polymer 42 (2001) 2395–2402, https://doi.org/10.1016/S0032-3861(00)00652-2.

[52] M. Norkhairunnisa, A. Azizan, M. Mariatti, H. Ismail, L. Sim, Thermal stability and electrical behavior of polydimethylsiloxane nanocomposites with carbon nanotubes and carbon black fillers, J. Compos. Mater. 46 (2012) 903–910, https://doi.org/10.1177/0021998311412985.

[53] M. Phillips, P. Zaghari, J. Eun Ryu, M. Zikry, Microstructural behavior of CNT-PDMS thin-films for multifunctional systems, Compos. Part A Appl. Sci. Manuf. 187 (2024) 108473, https://doi.org/10.1016/j.compositesa.2024.108473.

[54] C. Chen, X. Bu, Q. Feng, D. Li, Cellulose nanofiber/carbon nanotube conductive nano-network as a reinforcement template for polydimethylsiloxane polymopoly 10091000, https://doi.org/10.3390/polym10091000.

[55] O.-N. Hur, J.-H. Ha, S.-H. Park, Strain-sensing properties of multi-walled carbon nanotube/polydimethylsiloxane composites with different aspect ratio and filler contents, Materials 13 (2020) 2431, https://doi.org/10.3390/ma13112431.

[56] E. Magsipoc, Q. Zhao, G. Grasselli, 2D and 3D roughness characterization, Rock. Mech. Rock. Eng. 53 (2020) 1495–1519, https://doi.org/10.1007/s00603-019-01977-4.

[57] H.Y. Marghalani, Effect of filler particles on surface roughness of experimental composite series, J. Appl. Oral. Sci. 18 (2010) 59, https://doi.org/10.1590/S1678-77572010000100011.

[58] K.J. Kubiak, M.C.T. Wilson, T.G. Mathia, Ph Carval, Wettability versus roughness of engineering surfaces, Wear 271 (2011) 523–528, https://doi.org/10.1016/j.wear.2010.03.029.

[59] M. Palencia, University of Valle, surface free energy of solids by contact angle measurements, J. Sci. Technol. Appl. 2 (2017) 84–93, https://doi.org/10.34294/j.sta.17.2.17.

[60] Y. Tian, C. Hu, M. An, X. He, H. Wang, C. Yi, Fabrication and characterization of carbon nanotube filled PDMS hybrid membranes for enhanced ethanol recovery,
ACS Appl. Mater. Interfaces 15 (2023) 12294–12304, https://doi.org/10.1021/acsami.2c20553.

[61] J. Yan, B. Kim, Y.G. Jeong, Thermomechanical and electrical properties of PDMS/MWCNT composite films crosslinked by electron beam irradiation, J. Mater. Sci. 50 (2015) 5599–5608, https://doi.org/10.1007/s10853-015-9110-1.

[62] M. Luo, Y. Zhang, Y. Luo, J. Lu, A tension/pressure integrated resistive sensor comprising of a PDMS-LC-MWCNT composite, Sensors 21 (2021) 6078, https://doi.org/10.3390/s21186078.