Next Article in Journal
Optimization of Strain and Doping in Ge/GeSi Nanoscale Multilayers for GOI Short-Wave Infrared Imaging Applications
Previous Article in Journal
RETRACTED: Atta et al. Magnetic Ionic Liquid Nanocatalyst to Improve Mechanical and Thermal Properties of Epoxy Nanocomposites. Nanomaterials 2020, 10, 2325
Previous Article in Special Issue
Enhanced Degradation of Phenol in Aqueous Solution via Persulfate Activation by Sulfur-Doped Biochar: Insights into Catalytic Mechanisms and Structural Properties
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Nanomaterials
Volume 16
Issue 5
10.3390/nano16050294
nanomaterials-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Effects of Carbon Fillers on Electrical and Mechanical Properties of Water-Based Polymer Nanocomposites

by
Maryam Ehsani
1,†,
Marija Prosheva
2,†,
Katja Heise
1,
Jadranka Blazhevska Gilev
2,
Radmila Tomovska
3,4 and
Yvonne Joseph
1,*
1
Institute of Nanoscale and Biobased Materials, Technische Universität Bergakademie Freiberg, Gustav-Zeuner-Str. 3, 09599 Freiberg, Germany
2
Faculty of Technology and Metallurgy, Ss. Cyril and Methodius University in Skopje, Ruger Boskovic 16, 1000 Skopje, North Macedonia
3
POLYMAT, Facultad de Ciencias Químicas, University of the Basque Country UPV/EHU, Joxe Mari Korta Zentroa, Tolosa Etorbidea 72, 20018 Donostia-San Sebastián, Spain
4
IKERBASQUE, Basque Foundation of Science, Maria Diaz de Haro 3, 48013 Bilbao, Spain
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Nanomaterials 2026, 16(5), 294; https://doi.org/10.3390/nano16050294
Submission received: 21 January 2026 / Revised: 22 February 2026 / Accepted: 24 February 2026 / Published: 26 February 2026
(This article belongs to the Special Issue Synthesis, Electrical Properties and Applications of Carbon-Based Nanocomposites)
Browse Figures
Versions Notes

Abstract

Both the electrical conductivity and tailored mechanical characteristics—showing flexibility and structural integrity—are key properties of polymer composites. In this work, a novel, simple, and water-based strategy for synthesizing rGO-MWCNT/polymer composites was developed. Namely, carbon nanofillers in a mixture of reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) were incorporated in a waterborne methacrylic polymer matrix at loadings of 0.25, 0.5, and 1.0 wt.% nanofiller, and with rGO-to-MWCNT ratios of 10:1, 1:1, and 1:10 (w/w) at room temperature. Electrically conductive composites were obtained with all tested filler rates showing the highest conductivity (up to 8.2 × 10−3 Sm−1) for the MWCNT-rich filler due to the formation of a segregated network of the filler in the matrix. The mechanical properties of the composites—characterized by their Young’s modulus and elongation at break—strongly depended on both the filler incorporation rate and the rGO:MWCNT ratio. For instance, soft and flexible composites were obtained by incorporating 0.25 wt.% of the MWCNT-rich filler, which increased the elongation at break from 154.2% (neat polymer) to 252.4%. Overall, this study emphasizes the sensitive interplay between carbon filler introduction incorporating conductivity and the fillers’ impact on the mechanical properties of a polymer composite, both necessitating careful optimization for applications, e.g., in flexible electronics.

Graphical Abstract

1. Introduction

Wearable electronics are pushing the limits of human–machine interfaces. Current devices still rely on conventional rigid electronics, but flexible and stretchable systems are increasingly investigated to enable reliable data acquisition without restricting natural body movement [1,2]. A major challenge is designing materials that can endure large deformations while maintaining functionality and conforming to the skin. Advances in soft materials have enabled the development of mechanically deformable electronic systems with promising applications in biomedical engineering and flexible electronics [3,4]. Careful material selection and mechanical analysis are therefore essential to achieve conformal integration for monitoring pressure, strain, and bio-potentials. Soft polymers play a key role in improving flexibility and adhesion in wearable devices. Their mechanical performance, including stiffness and modulus, can be tailored through structural design or material combinations [5,6]. Polymer-based nanocomposites, which integrate flexible polymer matrices with nanoscale fillers, have emerged as attractive platforms for flexible electronics [7]. In addition to mechanical compliance, electronic applications require sufficient electrical conductivity. The incorporation of conductive nanofillers into polymer matrices provides an effective strategy for achieving this functionality [8]. Carbon-based nanomaterials—such as graphene (G), reduced graphene oxide (rGO), and carbon nanotubes (CNTs)—are widely explored as conductive fillers due to their outstanding electrical conductivity and mechanical characteristics [9,10,11,12,13]. Combining different carbon nanostructures into hybrid systems offers opportunities to tailor network formation, charge transport pathways, and deformation behavior [14,15,16,17,18,19,20,21].
Graphene-based materials provide a high specific surface area, good electrical conductivity, and mechanical flexibility. However, graphene sheets tend to restack due to strong van der Waals interactions, which reduces accessible surface area and limits effective network formation. In contrast, CNTs offer one-dimensional conductive pathways, high aspect ratios, and the ability to form percolated networks at relatively low loadings, although their dispersion in polymer matrices can be challenging. Integrating graphene derivatives with CNTs may help mitigate these individual limitations by promoting spatial separation of graphene sheets while facilitating network connectivity. The properties of graphene strongly depend on synthesis and reduction routes. Graphene oxide (GO) contains oxygen-containing functional groups that improve compatibility with polymers but reduce electrical conductivity. Partial reduction to rGO restores conductivity while retaining some functional groups beneficial for interfacial interactions [22,23,24]. CNTs, characterized by their hexagonal carbon structure and high aspect ratio, can contribute to electrical conductivity and influence stress distribution within polymer matrices [25,26,27].
Hybrid rGO–MWCNT systems have been widely investigated for enhancing electrical conductivity and modifying mechanical performance in polymer composites [28,29,30,31]. Reported improvements are often attributed to improved dispersion, interfacial interactions, and network formation [32,33,34,35,36]. CNTs can act as spacers between graphene sheets, potentially reducing restacking and facilitating the formation of interconnected conductive pathways [36,37,38,39]. However, it should be emphasized that hybridization does not inherently guarantee a synergistic mechanical reinforcement effect. The final properties strongly depend on filler ratio, dispersion state, interfacial adhesion, and processing method. Systematic evaluation of filler composition is therefore necessary to understand how hybrid architecture influences composite behavior [40,41]. Existing synthesis approaches for incorporating mixed carbon fillers frequently involve high temperatures, organic solvents, or complex processing routes that reduce sustainability and scalability [40,41,42,43,44,45,46]. Developing simple, low-temperature, and environmentally friendly fabrication methods remains an important objective.
In this work, a water-based strategy was developed to prepare rGO–MWCNT/polymer composites using aqueous dispersions. A waterborne MMA/BA/GMA copolymer (49.5/49.5/1 wt.%) was synthesized via seeded semi-continuous emulsion polymerization. This composition provides a glass transition temperature below room temperature, enabling spontaneous film formation under ambient conditions [47,48]. Hybrid filler dispersions were incorporated at total loadings up to 1 wt.%, and the influence of rGO/MWCNT ratios (1:1, 1:10, and 10:1) on morphology and tensile behavior was systematically investigated [47,48].
Rather than presuming synergistic reinforcement, the present study aims to elucidate how hybrid carbon architectures influence deformation mechanisms and mechanical response in waterborne polymer composites intended for flexible electronic applications.

2. Materials and Methods

Materials: Multi-walled carbon nanotubes (MWCNTs) with a length between 5 and 15 μm and diameters of 10–30 nm purchased from Sigma-Aldrich (St. Louis, MO, USA), an aqueous dispersion of graphene oxide (GO, 5 mg/mL, 80%) from ACS material, and ascorbic acid (ASA, 99%) from Acros-Organics (The Hague, The Netherlands) were used to prepare the fillers. Polyvinyl pyrrolidone (PVP, 10,000 g/mol) for rGO stabilization was purchased from Sigma-Aldrich. Alkyldiphenyloxide Disulfonate (Dowfax2A1, Dow Chemical Co., Midland, MI, USA), methyl methacrylate (MMA, 99.9%), and butyl acrylate (BA, 99.5%) from Qumidroga (Barcelona, Spain), glycidyl methacrylate (GMA, 97%) from Acros-Organics, and initiator potassium persulfate (KPS, 99%) from Sigma-Aldrich were used for polymer synthesis. Milli-Q ultrapure water was used for the preparation of dispersions and emulsions as a solvent.

2.1. rGO/MWCNTs Filler Preparation

The schematic representation of the synthesis of fillers is given in Figure 1. Before synthesis, GO dispersions in different amounts (Table 1) were sonicated to exfoliate the aggregated platelets using a bar sonicator (Sonifier 450, Branson Ultrasonics Corporation, Brookfield, CT, USA) for 15 min at 80% power on a 50% duty cycle and agitation of 200 rpm (Figure 1a). Separately, varying amounts of MWCNTs (Table 1) were sonicated in air for 90 min at 70% power, and a 50% duty cycle under the agitation of 200 rpm was performed to separate any agglomerated MWCNT bundles (Figure 1b). More details on this process can be found elsewhere [49].
The MWCNT pre-sonicated in air was added in the respective amounts to the pre-sonicated GO suspension and sonicated for an additional 2.5 min at 80% power, with a 50% duty cycle under 200 rpm agitation (Figure 1c). To obtain reduced graphene oxide, the GO/MWCNTs filler was subjected to chemical reduction. The reduction was performed as follows: first, 5 wt.% PVP was added to the GO/MWCNTs filler to colloidally stabilize the reduced nanoparticles, and the mixture was stirred for 30 min (Figure 1d). Then ASA was added according to the following ratio: solid reductant to filler = 5:1 (Figure 1e). To reduce the water content, the mixtures of 10:1 w/w and 1:1 w/w (GO/MWCNTs) were kept in an oven at 90 °C for 60 min. The 1:10 mixture was only kept at room temperature for 12 h because of its already low water content due to the low amount of GO dispersion used (Figure 1f). After the reduction, all three rGO/MWCNTs fillers were subjected to dialysis to remove the excess of PVP (Spectrum Labs membrane, molecular weight cut-off membrane (MWCO) 12–14 kDa).

2.2. Polymer Latex Preparation

For the synthesis of polymer dispersions as shown in Figure 2, seeded semi-continuous emulsion polymerization was employed. To obtain 150 g of polymer seed dispersion with 10% solids content, Dowfax 2A1 (2 wt.% based on the monomers), 134 g water, 7.5 g MMA, and 7.5 g BA were stirred in a 250 mL reactor for 10 min. The temperature was raised to 70 °C, and the initiator KPS aqueous solution (0.5 wt.% based on monomers) was added. The reaction was performed in a nitrogen atmosphere in a batch mode for 3 h (Figure 2a). Then, the prepared seed was used for the synthesis of the final polymer latex dispersion in a semi-continuous process. To obtain 900 g of final dispersion with 50% solid content, MMA/BA seed (27 g) and water (110 g) were stirred in a 1000 mL reactor for 10 min. When the temperature of the reactor reached 70 °C, an aqueous solution of KPS (2.24 g in 15.7 g of water) was inserted into the reactor. Subsequently, feeding of an aqueous solution made of Dowfax 2A1 45% (2 wt.% based on monomer), water (300 g), and a monomer mixture of MMA/BA/GMA in amounts 221.4 g/221.4 g/4.5 g was performed at a rate of 4.2 g/min. The reaction was performed in a nitrogen atmosphere, in semi-batch for 3 h, and afterwards in batch for 2 h to achieve full monomer conversion (Figure 2b).

2.3. Preparation of Nanocomposite Dispersions

The rGO/MWCNTs/polymer composites were prepared by mixing the dispersions. Namely, appropriate amounts of the three rGO/MWCNTs (10:1 wt.%, 1:1 wt.%, and 1:10 wt.%) aqueous dispersions were added into polymer latex dispersion (0.25 wt.%, 0.5 wt.%, and 1 wt.% based on the solid content), so dispersions with different rGO/MWCNT concentrations were obtained. After the addition of the fillers, the mixtures were continuously stirred at room temperature for 3 h at 150 rpm.

2.4. Characterization

The method of specimen preparation and characterization of filler and composites is described in Figure 3.
The filler dispersions were drop-coated on a glass substrate and left to dry for 12 h before performing Raman and conductivity measurements. A confocal Raman microscope from Renishaw was used to perform measurements in backscattering geometry using a Labram HR 800 Horiba Jobin Yvon spectrometer (HORIBA, Kyoto, Japan) equipped with a 600 mm−1 grating and thermoelectrically cooled charge-coupled device detector for investigation of the chemical composition and structure of the rGO/MWCNTs filler samples. The Raman scattering was exciting with a 532 nm line of a doubled frequency Nd-YAG laser using laser power of ca. 2.5 mW. By passing the laser beam through a microscope objective (Olympus, Tokyo, Japan), the linearly polarized laser light was focused on the surface of the rGO/MWCNTs specimen. Each spectrum was recorded using 30 accumulations with an exposure time of 5 s. With a four-point handheld probe (FPP 5000 Miller, Veeco-Miller Design, Azusa, CA, USA), the conductivities of the different fillers were measured. Furthermore, Transmission Electron Microscopy (TEM, Tecnai G2 20 Twin, FEI Company, Waltham, MA, USA) was used to observe the morphology of the rGO/MWCNTs fillers drop-coated on TEM grids.
Solid samples from unfilled polymer and the composites were prepared using silicone molds in which the latexes were cast and dried at 25 °C and 55% relative humidity (standard atmospheric conditions). The obtained solid samples were cut with a die cutter for further analysis. Scanning Electron Microscopy (SEM, Quanta 250 e-SEM, Philips Tecna, Amsterdam, The Netherlands) was employed to observe the morphology of the neat polymer and nanocomposite samples. Cross-sectional cuts were prepared by breaking samples previously frozen in liquid nitrogen.
To determine the mechanical properties of the nanocomposite materials, tensile specimens (15 mm × 3.5 mm × 0.5 mm) were cut, and the measurements were performed using TA.HD plus texture analyzer (Stable Micro Systems Ltd., Godalming, UK) with a constant strain velocity of 1.5 mm s−1. The length between the jaws was 15 mm, and the experiment’s nominal strain rate was 0.1 Hz. Young’s modulus and Offset Yield stress were estimated.
The unfilled polymer and the composites were spin-coated (600 rpm for 20 s followed by 3000 rpm for 6 s) on gold-coated interdigitated electrodes. Afterwards, all composite films were dried under ambient conditions for 2 h. The thickness of composite films was measured at ~10 ± 0.3 µm using a 3D laser microscope (LEXT OLS4000-Olympus, Tokyo, Japan), while their conductivities were determined with a handheld multimeter. All the measurements were carried out at room temperature.

3. Results and Discussion

3.1. Filler Properties

In the preparation of rGO/MWCNTs fillers, three different weight ratios of rGO:MWCNTs, 10:1, 1:1, and 1:10 (w/w), were selected. As the aqueous dispersions of the rGO/MWCNTs fillers were stabilized with PVP, no precipitation was observed even after longer storage times (Figure 4a). A similar approach to rGO stabilization in aqueous dispersion was demonstrated by Arzac et al. [46] using the same stabilizing agent (PVP).
The investigation of the chemical composition and structure of the rGO/MWCNTs fillers before composite formation was carried out with Raman spectroscopy. The Raman spectra of rGO/MWCNTs fillers with different ratios of the rGO and MWCNTs are shown in Figure 4b. Raman results for all rGO/MWCNTs fillers demonstrate the presence of four different vibration peaks G, D, 2D, and D + D′ that correspond to sp2 hybridized carbon (G peak at ~1590 cm−1), sp3 hybridized carbon (D and 2D at ~1350 and 2702 cm−1), and combination mode (D + D′) at 2945 cm−1 as a sign of atomic insertions. The 2D band of rGO/MWCNTs may be attributed to the presence of rGO on the MWCNTs, and the D′ band is caused by defects generated by an internal double-resonance process.
The intensity ratio of the signal D and G (ID/IG) is presented in Table 2; the ratios reflect the level of defects or disorder versus graphitic order in carbon materials, with higher values indicating more defects and lower values indicating a more ordered structure. In our case, the values are similar for all samples, and they are relatively high, which is likely due to a high number of defects in both carbon structures of the fillers [50]. This fact simply illustrates the significant presence of still non-reduced-oxygen functional groups [51].
The electrical conductivities of the dried filler mixtures are given in Table 2. Strong π-π interfacial coupling between the MWCNTs and the rGO that promotes charge carrier mobility between both rGO and MWCNTs, as well as van der Waals interactions between individual rGO nanoparticles and MWCNTs nanoparticles, presumably occurs. The conductivity increases with increasing MWCNT content, presumably due to higher conductivity and longer length of the MWCNT compared to the rGO flake size, both enabling more and efficient percolation pathways.
To evaluate the structure of the fillers, they were subjected to TEM analysis. Figure 5 presents the TEM images of the rGO:MWCNTs fillers with different ratios of rGO and MWCNTs. The result clearly illustrates that rGO platelets are well exfoliated in the dispersion, often single-layered, and CNTs are mostly disentangled and individual. The MWCNTs probably interact with the rGO by building stacking π-π interactions or even connecting a few rGO platelets. By increasing the MWCNT quantity (from Figure 5a–c), the nanotubes are more aggregated and entangled, covering the rGO platelets. The better interaction between them and the most likely higher conductivity of the MWCNT are presumably responsible for the observed increasing conductivity of the filler with increasing MWCNT quantity.

3.2. Nanocomposite Films

The nanocomposites containing 1 wt.% fillers with different rGO:MWCNT ratios (1:10, 1:1, and 10:1(w/w)) were studied. Furthermore, in the case of the 10:1 (w/w) rGO:MWCNT, the composites were prepared to contain different loadings of the fillers of 0.25, 0.5, and 1 wt.%. Figure 6 shows photos of all the composites. The darker color of the composites was observed with increasing the MWCNTs quantity compared to the other films due to the homogenous dispersion of rGO and MWCNTs into the polymer. It is worth mentioning that after mixing polymer nanoparticles and the filler mixtures in colloidal aqueous dispersion, the platelets and the MWCNTs are adsorbed on the surface of the polymer particles. This configuration avoided or at least minimized the aggregation of the inorganic fillers during the composite films’ formation with water evaporation and preserved a homogenous filler distribution in the dried composite, as shown by SEM investigations below.
To evaluate this possibility and the size and interactions of the rGO:MWCNTs nanoparticles in the composites, cross-section cuts of the prepared composite films were subjected to SEM analysis (Figure 7, Figure A1 and Figure A2 (please check Appendix A)).
Figure 7 shows the SEM images of the composites. As can be seen in all composites, the carbon nanofillers with embedded white-grey structures are homogenously distributed into the polymer matrix with a dark continuous appearance. Nevertheless, MWCNTs appear as thinner and larger structures, as is shown in Figure 7e, where the filler contains a tenfold higher amount of MWCNTs than rGO. This morphology of a segregated network, like the distribution of the graphene-based filler into the polymer matrix, is typical for waterborne composites [52]. However, it is worth noting that at a low filler amount (0.25 and 0.5 wt.%, shown in Figure 7a,b), no aggregation was observed in the morphology of rGO-MWCNTs. As a result, the distribution of the fillers is much more homogeneous, whereas the composites containing 1 wt.% filler platelets have a more inhomogeneous structure and larger areas of neat polymer films and aggregates. The exception to this may be observed in the case of a 1:10 (w/w) ratio filler (Figure 7e), showing a very nice, segregated network with an abundant amount of MWCNTs presented.
The electrical conductivities of the composites are given in Table 3. Compared to the neat polymer, the conductivity of all composites was enhanced by several orders of magnitude. Interestingly, increasing the filler content of rGO:MWCNTs (10:1) within the composites from 0.25% to 1% does not significantly influence their conductivity. Possibly, the higher filler content cannot generate more percolation pathways due to filler aggregation as observed in SEM. Obviously, at a content of 0.25%, most of the percolation pathways have been formed. When increasing the MWCNTs concentration, the electrical conductivity of the composites strongly increased by an order of magnitude comparable with the conductivities of the filler alone.
Figure 8a presents the tensile stress–strain behavior of the nanocomposites in dependence on the loading range of 10:1 filler into a polymer under stress, whereas in Figure 8b, the effect of different ratios of rGO and MWCNTs within the filler (10:1, 1:1, and 1:10 (w/w)) in the polymer matrix is given. The mechanical properties determined from these curves are given in Table 4.
Figure 8 shows the significant strain hardening for all samples according to the results given in Table 4. Surprisingly, the neat polymer presents a very high value of Young’s modulus, high offset yield and maximum stress, and low strain rate at the maximum. The reason may be the presence of epoxy groups of GMA monomers with the ability to react with many functional groups, which makes the polymer stiffer. At low loading of the fillers (0.25 and 0.5 wt.%) in the polymer matrix, surprisingly, the composites are less stiff but softer than the neat polymer and much more stretchable, showing elongation of 304.6% and 238.4%, respectively. By increasing the loading range from 0.25 wt.% to 1 wt.%, the elongation decreased continuously to 154.9%, which confirms the stronger interaction between filler and matrix. Furthermore, the elongation at break significantly increased to 252.4% and 243.6% by incorporation of MWCNT-rich fillers of 1:1 and 1:10 into the polymer, respectively.
At lower filler loadings, the composite exhibits a softer mechanical response due to the limited polymer–filler interfacial area and the absence of a percolated filler network. The reduced interfacial contact results in a smaller fraction of immobilized polymer chains, allowing greater matrix chain mobility. In addition, isolated filler particles at low concentrations are less effective in stress transfer, causing the mechanical behavior to be dominated by the polymer matrix rather than filler reinforcement.
A lack of interaction between the filler and the polymer phases is usually the reason for the mechanical weakening of the polymer composites compared to the neat polymer.
Nevertheless, the impressive improvement in the flexibility of the same composites, almost threefold, eliminates this possibility and indicates excellent interaction.
Compared to the neat polymer, for all rGO-MWCNTs (10:1) composites, the stress at break and the strain at break increased, while Young’s modulus and the offset yield stress decreased. This behavior is opposite to that obtained in similar materials with individual rGO [52] and MWCNTs [53], in which cases Young’s modulus of polymer always increased with the loading of the fillers [53,54]. In our case, as observed in the SEM and postulated during blending, the filler containing mainly rGO has finely dispersed and binds presumably by a small number of hydrogen bonds to the polymer latex surface before and after drying as described above. This may hinder polymer–polymer interaction, especially the entanglement of the polymer chains, in which the rGO-rich filler behaves in small concentrations as a plasticizer. This fact leads to a decreased strength of the matrix and an increased elongation at break, which confirms the ductility of the material and its ability for deformation without a break. By increasing the loading weight ratio to 1 wt.% rGO-MWCNTs (10:1) within the composite, the value of all tensile characteristics is close to that of the neat polymer again. As the SEM image indicated in this case, the distribution of the rGO-rich filler is not homogenous for 1 wt.%, as in the 0.25 wt.% and 0.5 wt.% samples, indicating agglomeration of the filler. Therefore, this sample shows similar tensile properties to the neat polymer and higher stiffness. However, the elongation at break is not reduced by the addition of a higher filler ratio, as we expected; the reason is due to the polymer–filler interaction and stress transferring.
Also, when going from rGO-rich fillers to MWCNTs-rich fillers, a plasticizing effect can be observed, which makes the film softer and more flexible. Here, it can be assumed that, even when the filler material is finely distributed, the disturbance of the polymer–polymer interaction (i.e., entanglement) is probably smaller due to the 1D structure compared to the 2D structure of rGO. However, MWCNTs are assumed to form a weak interfacial interaction with the polymer compared to rGO, due to fewer hydrophilic groups on their surface. This fact induces the debonding of nanoscale fillers from the polymer matrix during loading, possibly weakening the polymer matrix as indicated by the decreased strain at the break with increasing the MWCNTs content [55,56,57,58,59]. While pristine polymer exhibits a modulus of 0.19 MPa, the modulus of all composites except 1 wt.% rGO:MWCNTs 10:1 (0.21 MPa) decreased. A more relevant increase in stress and strain at break has been observed in the case of samples containing rGO:MWCNTs 1:1 (w/w) filler, with its stress at break of 14.26 MPa and strain at break of 3.18 MPa. From the enhancement in tensile properties of the polymer after the addition of all filler samples, it can be concluded that all samples behave as soft and ductile materials. Although all samples demonstrated close values, the samples containing 0.25 wt.% rGO:MWCNTs 10:1 (w/w), 0.5 wt.% rGO:MWCNTs, and rGO:MWCNTs 1:10 (w/w) fillers demonstrated a combination of lower Young’s modulus and higher stress and strain values, which can be considered as a softer material with higher viscoelastic properties among other introduced composites.

4. Conclusions

Conductive nanocomposite films based on a waterborne methacrylic polymer matrix and hybrid carbon nanofillers were successfully prepared using a fully aqueous processing route. The mechanical and electrical properties of the films were tailored by varying both the rGO/MWCNT weight ratio and the total filler loading (0.25–1 wt.%). Morphological investigations (TEM and SEM) demonstrated that increasing the MWCNT content led to more pronounced nanotube entanglement and partial coverage of rGO platelets, influencing the formation of conductive pathways. The electrical conductivity of both the mixed fillers and the composite films increased with higher MWCNT fractions, reaching the highest values for the MWCNT-rich system (rGO:MWCNT = 1:10, w/w). These results indicate that MWCNTs play a dominant role in establishing effective charge transport networks within the polymer matrix. In terms of mechanical behavior, the incorporation of hybrid fillers modified the deformation response of the polymer rather than producing classical stiffness reinforcement. Composites containing 0.25 wt.% and 0.5 wt.% rGO-rich fillers (10:1) exhibited a reduction in Young’s modulus accompanied by an increase in elongation at break. Similar trends were observed for MWCNT-rich systems, resulting in softer and more flexible films compared to the neat polymer. The observed mechanical response suggests that the hybrid rGO/MWCNT architecture influences stress distribution and fracture propagation within the matrix. While rGO sheets provide extended interfacial contact with polymer chains, MWCNTs may act as bridging elements that alter filler–filler interactions and reduce rigid aggregation (Figure 9). This structural arrangement likely promotes energy dissipation and enhanced chain mobility, leading to decreased stiffness and improved ductility.
Overall, the results demonstrate that hybrid carbon nanofillers can be used to tune the balance between electrical conductivity and mechanical flexibility in waterborne polymer composites. The developed films exhibit promising characteristics for flexible and wearable electronic applications, where mechanical compliance and conductivity must be simultaneously achieved. Future studies involving direct comparison with single-filler systems will further clarify the extent of hybrid effects in such materials.

Author Contributions

Writing—original draft, M.E.; Methodology, Experiments, analysis, M.E. and M.P.; Investigation, M.E. and M.P.; Supervision, Y.J. and R.T.; Conceptualization, validation, review, and editing, all authors. All authors have read and agreed to the published version of the manuscript.

Funding

This research was partially supported by the Free State of Saxony scholarship (Landesgraduiertenstipendium-G293) provided by the research foundation of Germany and a research grant from NATO (SfP-G5244). We thank all who supported us at POLYMAT Institute (University of the Basque Country, Spain) and TU Bergakademie Freiberg, Germany, for the synthesis and characterization processes.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

Appendix A

The SEM image from the top view of the films containing 1 wt.% different ratios of hybrids is shown in Figure A1 and Figure A2 in different resolutions of 1 and 4 µm, respectively. The presence of bundles and the restacking of the MWCNTs and the graphene sheets could be observed. For these composite films, an important amount of the nanofillers was noticeable on the top surface. It may be observed from Figure A1 that small-sized rGO nano-platelets are distributed around the polymer particles in Figure A2, where the MWCNTs content is very low. By increasing it, in Figure A1 and Figure A2, the MWCNTs surrounding the particles could be observed on the top surface of the films.
Nanomaterials 16 00294 g0a1
Figure A1. SEM images of composite films containing 1 wt.% rGO-MWCNT with ratios of (a) 10:1, (b) 1:1, and (c) 1:10.
Figure A1. SEM images of composite films containing 1 wt.% rGO-MWCNT with ratios of (a) 10:1, (b) 1:1, and (c) 1:10.
Nanomaterials 16 00294 g0a1
Nanomaterials 16 00294 g0a2
Figure A2. SEM images of the top surface area of composite films containing 1 wt.% rGO-MWCNTs with ratios of (a) 10:1, (b) 1:1, and (c) 1:10.
Figure A2. SEM images of the top surface area of composite films containing 1 wt.% rGO-MWCNTs with ratios of (a) 10:1, (b) 1:1, and (c) 1:10.
Nanomaterials 16 00294 g0a2

References

  1. Wang, X.; Liu, Z.; Zhang, T. Flexible Sensing Electronics for Wearable/Attachable Health Monitoring. Small 2017, 13, 1602790. [Google Scholar] [CrossRef]
  2. Trung, T.Q.; Lee, N.-E. Flexible and Stretchable Physical Sensor Integrated Platforms for Wearable Human-Activity Moni-toringand Personal Healthcare. Adv. Mater. 2016, 28, 4338–4372. [Google Scholar] [CrossRef]
  3. Wang, C.; Xia, K.; Wang, H.; Liang, X.; Yin, Z.; Zhang, Y. Advanced Carbon for Flexible and Wearable Electronics. Adv. Mater. 2019, 31, e1801072. [Google Scholar] [CrossRef]
  4. Kim, D.-H.; Rogers, J.A. Stretchable Electronics: Materials Strategies and Devices. Adv. Mater. 2008, 20, 4887–4892. [Google Scholar] [CrossRef]
  5. Mohan, A.M.V.; Kim, N.; Gu, Y.; Bandodkar, A.J.; You, J.-M.; Kumar, R.; Kurniawan, J.F.; Xu, S.; Wang, J. Merging of Thin- and Thick-Film Fabrication Technologies: Toward Soft Stretchable “Island–Bridge” Devices. Adv. Mater. Technol. 2017, 2, 1600284. [Google Scholar] [CrossRef]
  6. Lipomi, D.J. Stretchable Figures of Merit in Deformable Electronics. Adv. Mater. 2016, 28, 4180–4183. [Google Scholar] [CrossRef] [PubMed]
  7. Yogeswaran, N.; Khan, S.; Dang, W.; Polat, E.O.; Lorenzelli, L.; Vinciguerra, V.; Dahiya, R. Tuning electrical conductivity of CNT-PDMS nanocomposites for flexible electronic applications. In 2015 IEEE 15th International Conference on Nanotechnology (IEEE-NANO), Rome, Italy, 27–30 July 2015; IEEE: New York, NY, USA, 2015; pp. 1441–1444. [Google Scholar][Green Version]
  8. Winey, K.I.; Kashiwagi, T.; Mu, M. Improving Electrical Conductivity and Thermal Properties of Polymers by the Addition of Carbon Nanotubes as Fillers. MRS Bull. 2007, 32, 348–353. [Google Scholar] [CrossRef]
  9. Sun, X.; Sun, J.; Li, T.; Zheng, S.; Wang, C.; Tan, W.; Zhang, J.; Liu, C.; Ma, T.; Qi, Z.; et al. Flexible Tactile Electronic Skin Sensor with 3D Force Detection Based on Porous CNTs/PDMS Nanocomposites. Nanomicro. Lett. 2019, 11, 57. [Google Scholar] [CrossRef] [PubMed]
  10. Xue, L.; Wang, W.; Guo, Y.; Liu, G.; Wan, P. Flexible polyaniline/carbon nanotube nanocomposite film-based electronic gas sensors. Sens. Actuators B Chem. 2017, 244, 47–53. [Google Scholar] [CrossRef]
  11. Yang, W.; Zhao, Y.; He, X.; Chen, Y.; Xu, J.; Li, S.; Yang, Y.; Jiang, Y. Flexible conducting polymer/reduced graphene oxide films: Synthesis, characterization, and electrochemical performance. Nanoscale Res. Lett. 2015, 10, 222. [Google Scholar] [CrossRef] [PubMed]
  12. Kammoun, M.; Berg, S.; Ardebili, H. Flexible thin-film battery based on graphene-oxide embedded in solid polymer electrolyte. Nanoscale 2015, 7, 17516–17522. [Google Scholar] [CrossRef] [PubMed]
  13. Wang, Y.; Wang, Y.; Yang, Y. Graphene-Polymer Nanocomposite-Based Redox-Induced Electricity for Flexible Self-Powered Strain Sensors. Adv. Energy Mater. 2018, 8, 1800961. [Google Scholar] [CrossRef]
  14. Jian, M.; Wang, C.; Wang, Q.; Wang, H.; Xia, K.; Yin, Z.; Zhang, M.; Liang, X.; Zhang, Y. Advanced carbon materials for flexible and wearable sensors. Sci. China Mater. 2017, 60, 1026–1062. [Google Scholar] [CrossRef]
  15. Qi, H.; Schulz, B.; Vad, T.; Liu, J.; Mäder, E.; Seide, G.; Gries, T. Novel Carbon Nanotube/Cellulose Composite Fibers as Mul-tifunctional Materials. ACS Appl. Mater. Interfaces 2015, 7, 22404–22412. [Google Scholar] [CrossRef]
  16. Wernik, J.M.; Meguid, S.A. Recent Developments in Multifunctional Nanocomposites Using Carbon Nanotubes. Appl. Mech. Rev. 2010, 63, 050801. [Google Scholar] [CrossRef]
  17. Lima, R.M.A.P.; Alcaraz-Espinoza, J.J.; da Silva, F.A.G.; de Oliveira, H.P. Multifunctional Wearable Electronic Textiles Using Cotton Fibers with Polypyrrole and Carbon Nanotubes. ACS Appl. Mater. Interfaces 2018, 10, 13783–13795. [Google Scholar] [CrossRef] [PubMed]
  18. Kaidarova, A.; Khan, M.A.; Marengo, M.; Swanepoel, L.; Przybysz, A.; Muller, C.; Fahlman, A.; Buttner, U.; Geraldi, N.R.; Wilson, R.P.; et al. Wearable multifunctional printed graphene sensors. NPJ Flex. Electron. 2019, 3, 15. [Google Scholar] [CrossRef]
  19. Matos, C.F.; Galembeck, F.; Zarbin, A.J. Multifunctional and environmentally friendly nanocomposites between natural rubber and graphene or graphene oxide. Carbon 2014, 78, 469–479. [Google Scholar] [CrossRef]
  20. Kumar, S.; Raj, S.; Jain, S.; Chatterjee, K. Multifunctional biodegradable polymer nanocomposite incorporating graphene-silver hybrid for biomedical applications. Mater. Des. 2016, 108, 319–332. [Google Scholar] [CrossRef]
  21. Du, J.; Cheng, H.-M. The Fabrication, Properties, and Uses of Graphene/Polymer Composites. Macromol. Chem. Phys. 2012, 213, 1060–1077. [Google Scholar] [CrossRef]
  22. Emiru, T.F.; Ayele, D.W. Controlled synthesis, characterization and reduction of graphene oxide: A convenient method for large scale production. Egypt. J. Basic Appl. Sci. 2017, 4, 74–79. [Google Scholar] [CrossRef]
  23. Tan, H.; Wang, D.; Guo, Y. Thermal Growth of Graphene: A Review. Coatings 2018, 8, 40. [Google Scholar] [CrossRef]
  24. Shahriary, L.; Anjali, A.A. Graphene oxide synthesized by using modified hummers approach. Int. J. Renew. Energy Environ. Eng. 2014, 2, 58–63. [Google Scholar]
  25. Kim, Y.J.; Shin, T.S.; Choi, H.D.; Kwon, J.H.; Chung, Y.-C.; Yoon, H.G. Electrical conductivity of chemically modified multi-walled carbon nanotube/epoxy composites. Carbon 2005, 43, 23–30. [Google Scholar] [CrossRef]
  26. Wang, B.; Li, J.; Liu, Y.; Gao, Y. Reduced graphene oxide/carbon nanotubes nanohybrids as preformed reinforcement for pol-ystyrene composites. J. Appl. Polym. Sci. 2017, 134, 45054. [Google Scholar] [CrossRef]
  27. Aqel, A.; El-Nour, K.M.A.; Ammar, R.A.; Al-Warthan, A. Carbon nanotubes, science and technology part (I) structure, syn-thesis and characterisation. Arab. J. Chem. 2012, 5, 1–23. [Google Scholar] [CrossRef]
  28. Valentini, L.; Bittolo Bon, S.; Hernández, M.; Lopez-Manchado, M.A.; Pugno, N.M. Nitrile butadiene rubber composites rein-forced with reduced graphene oxide and carbon nanotubes show superior mechanical, electrical and icephobic properties. Compos. Sci. Technol. 2018, 166, 109–114. [Google Scholar] [CrossRef]
  29. Chatterjee, S.; Nafezarefi, F.; Tai, N.H.; Schlagenhauf, L.; Nüesch, F.A.; Chu, B. Size and synergy effects of nanofiller hybrids including graphene nanoplatelets and carbon nanotubes in mechanical properties of epoxy composites. Carbon 2012, 50, 5380–5386. [Google Scholar] [CrossRef]
  30. Li, Y.; Yang, T.; Yu, T.; Zheng, L.; Liao, K. Synergistic effect of hybrid carbon nantube–graphene oxide as a nanofiller in en-hancing the mechanical properties of PVA composites. J. Mater. Chem. 2011, 21, 10844–10851. [Google Scholar] [CrossRef]
  31. Kumar, S.; Sun, L.L.; Caceres, S.; Li, B.; Wood, W.; Perugini, A.; Maguire, R.G.; Zhong, W.H. Dynamic synergy of graphitic nanoplatelets and multi-walled carbon nanotubes in polyetherimide nanocomposites. Nanotechnology 2010, 21, 105702. [Google Scholar] [CrossRef]
  32. Patil, V.; Dennis, R.V.; Rout, T.K.; Banerjee, S.; Yadav, G.D. Graphene oxide and functionalized multi walled carbon nanotubes as epoxy curing agents: A novel synthetic approach to nanocomposites containing active nanostructured fillers. RSC Adv. 2014, 4, 49264–49272. [Google Scholar] [CrossRef]
  33. Gong, L.-X.; Pei, Y.-B.; Han, Q.-Y.; Zhao, L.; Wu, L.-B.; Jiang, J.-X.; Tang, L.-C. Polymer grafted reduced graphene oxide sheets for improving stress transfer in polymer composites. Compos. Sci. Technol. 2016, 134, 144–152. [Google Scholar] [CrossRef]
  34. Rafiee, M.A.; Rafiee, J.; Wang, Z.; Song, H.; Yu, Z.-Z.; Koratkar, N. Enhanced mechanical properties of nanocomposites at low graphene content. ACS Nano 2009, 3, 3884–3890. [Google Scholar] [CrossRef]
  35. Bisht, A.; Dasgupta, K.; Lahiri, D. Evaluating the effect of addition of nanodiamond on the synergistic effect of graphene-carbon nanotube hybrid on the mechanical properties of epoxy based composites. Polym. Test. 2020, 81, 106274. [Google Scholar] [CrossRef]
  36. Bagotia, N.; Choudhary, V.; Sharma, D.K. Synergistic effect of graphene/multiwalled carbon nanotube hybrid fillers on me-chanical, electrical and EMI shielding properties of polycarbonate/ethylene methyl acrylate nanocomposites. Compos. Part B Eng. 2019, 159, 378–388. [Google Scholar] [CrossRef]
  37. Sa, K.; Mahakul, P.C.; Subramanyam, B.; Raiguru, J.; Das, S.; Alam, I.; Mahanandia, P. Effect of reduced graphene oxide-carbon nanotubes hybrid nanofillers in mechanical properties of polymer nanocomposites. IOP Conf. Ser. Mater. Sci. Eng. 2018, 338, 12055. [Google Scholar] [CrossRef]
  38. Capezza, A.; Andersson, R.L.; Ström, V.; Wu, Q.; Sacchi, B.; Farris, S.; Hedenqvist, M.S.; Olsson, R.T. Preparation and Com-parison of Reduced Graphene Oxide and Carbon Nanotubes as Fillers in Conductive Natural Rubber for Flexible Electronics. ACS Omega 2019, 4, 3458–3468. [Google Scholar] [CrossRef] [PubMed]
  39. Cai, D.; Song, M.; Xu, C. Highly Conductive Carbon-Nanotube/Graphite-Oxide Hybrid Films. Adv. Mater. 2008, 20, 1706–1709. [Google Scholar] [CrossRef]
  40. Yang, Y.; Shen, H.; Yang, J.; Gao, K.; Wang, Z.; Sun, L. Synergistic effect of reduced graphene oxide/carbon nanotube hybrid papers on cross-plane thermal and mechanical properties. RSC Adv. 2022, 12, 19144–19153. [Google Scholar] [CrossRef]
  41. Prosheva, M.; Ehsani, M.; Joseph, Y.; Tomovska, R.; Blazhevska Gilev, J. Waterborne polymer composites containing hybrid graphene/carbon nanotube filler: Effect of graphene type on properties and performance. Polym. Compos. 2023, 44, 5188–5200. [Google Scholar] [CrossRef]
  42. Ndlwana, L.; Raleie, N.; Dimpe, K.M.; Ogutu, H.F.; Oseghe, E.O.; Motsa, M.M.; Msagati, T.A.M.; Mamba, B.B. Sustainable hydro-thermal and solvothermal synthesis of advanced carbon materials in multidimensional applications: A review. Materials 2021, 14, 5094. [Google Scholar] [CrossRef] [PubMed]
  43. Ali, Z.; Yaqoob, S.; Yu, J.; D’Amore, A.; Fakhar-e-Alam, M. A comparative review of processing methods for graphene-based hybrid filler polymer composites and enhanced mechanical, thermal, and electrical properties. J. King Saud Univ.-Sci. 2024, 36, 103457. [Google Scholar] [CrossRef]
  44. Abu-Zurayk, R.; Khalaf, A.; Alnairat, N.; Waleed, H.; Bozeya, A.; Abu-Dalo, D.; Rabba’a, M. Green polymer nano-composites: Bridging material innovation with sustainable industrial practices. Front. Mater. 2025, 12, 1701086. [Google Scholar] [CrossRef]
  45. Ali, Z.; Yaqoob, S.; Yu, J.; D’Amore, A. Critical review on the characterization, preparation, and enhanced mechanical, thermal, and electrical properties of carbon nanotubes and their hybrid filler polymer composites for various applications. Compos. Part C Open Access 2024, 13, 100434. [Google Scholar] [CrossRef]
  46. Arzac, A.; Leal, G.P.; Fajgar, R.; Tomovska, R. Comparison of the Emulsion Mixing and In Situ Polymerization Techniques for Synthesis of Water-Borne Reduced Graphene Oxide/Polymer Composites: Advantages and Drawbacks. Part. Part. Syst. Charact. 2014, 31, 143–151. [Google Scholar] [CrossRef]
  47. Ehsani, M.; Rahimi, P.; Joseph, Y. Structure-Function Relationships of Nanocarbon/Polymer Composites for Chemiresistive Sensing: A Review. Sensors 2021, 21, 3291. [Google Scholar] [CrossRef]
  48. Trajcheva, A.; Elgoyhen, J.; Ehsani, M.; Joseph, Y.; Gilev, J.B.; Tomovska, R. Advanced Nanostructured All-Waterborne Thiol-Ene/Reduced Graphene Oxide Humidity Sensors with Outstanding Selectivity. Adv. Mater. Technol. 2024, 9, 2400114. [Google Scholar] [CrossRef]
  49. Prosheva, M.; Ehsani, M.; Pérez-Martínez, B.T.; Blazevska Gilev, J.; Joseph, Y.; Tomovska, R. Dry sonication process for prep-aration of hybrid structures based on graphene and carbon nanotubes usable for chemical sensors. Nanotechnology 2021, 32, 185601. [Google Scholar] [CrossRef]
  50. Jeong, S.Y.; Jeong, S.; Lee, S.W.; Kim, S.T.; Kim, D.; Jeong, H.J.; Han, J.T.; Baeg, K.-J.; Yang, S.; Jeong, M.S.; et al. Enhanced response and sensitivity of self-corrugated graphene sensors with anisotropic charge distribution. Sci. Rep. 2015, 5, 11216. [Google Scholar] [CrossRef]
  51. Janata, J. Principles of Chemical Sensors; Springer: Berlin/Heidelberg, Germany, 2010. [Google Scholar]
  52. Qi, P.; Vermesh, O.; Grecu, M.; Javey, A.; Wang, Q.; Dai, H.; Peng, S.; Cho, K.J. Toward Large Arrays of Multiplex Function-alized Carbon Nanotube Sensors for Highly Sensitive and Selective Molecular Detection. Nano Lett. 2003, 3, 347–351. [Google Scholar] [CrossRef] [PubMed]
  53. Spasevska, D.; Leal, G.P.; Fernández, M.; Gilev, J.B.; Paulis, M.; Tomovska, R. Crosslinked reduced graphene oxide/polymer composites via in situ synthesis by semicontinuous emulsion polymerization. RSC Adv. 2015, 5, 16414–16421. [Google Scholar] [CrossRef]
  54. Pérez-Martínez, B.T.; Farías-Cepeda, L.; Ovando-Medina, V.M.; Asua, J.M.; Rosales-Marines, L.; Tomovska, R. Miniemulsion copolymerization of (meth)acrylates in the presence of functionalized multiwalled carbon nanotubes for reinforced coating applications. Beilstein J. Nanotechnol. 2017, 8, 1328–1337. [Google Scholar] [CrossRef] [PubMed]
  55. Voinova, M.V.; Rodahl, M.; Jonson, M.; Kasemo, B. Viscoelastic Acoustic Response of Layered Polymer Films at Fluid-Solid Interfaces: Continuum Mechanics Approach. Phys. Scr. 1999, 59, 391–396. [Google Scholar] [CrossRef]
  56. Gupta, R.; Kumar, G.; Bisaria, H.; Zafar, S. Effect of graphene nanoparticles on electrical, mechanical and viscoelastic behavior of CFRP multifunctional multiscale composites. Polym. Compos. 2025, 46, 6885–6899. [Google Scholar] [CrossRef]
  57. Ebrahimi, F.; Nopour, R.; Dabbagh, A. Effects of polymer’s viscoelastic properties and curved shape of the CNTs on the dynamic response of hybrid nanocomposite beams. Waves Random Complex Media 2025, 35, 1411–1428. [Google Scholar] [CrossRef]
  58. Moradi, A.; Ansari, R.; Hassanzadeh-Aghdam, M.K.; Jamali, J. Evaluating the role of agglomerated carbon nanotubes in the effective properties of polymer nanocomposites: An efficient micromechanics-based finite element framework. Comput. Mater. Sci. 2025, 246, 113337. [Google Scholar] [CrossRef]
  59. UrRehman, T.; Khan, S.A.; Shah, L.A.; Fu, J. Gum arabic-CNT reinforced hydrogels: Dual-function materials for strain sensing and energy storage in next-generation supercapacitors. Mater. Adv. 2025, 6, 1288–1299. [Google Scholar] [CrossRef]
Nanomaterials 16 00294 g001
Figure 1. Preparation of rGO-MWCNT dispersion. (a) Preparation of GO dispersion; (b) Preparation of MWCNT; (c) Preparation of GO/MWCNT dispersion; (d) Dispersion stabilization with PVP; (e) Reduction with ascorbic acid to achieve the rGO/MWCNT dispersion; (f) Reduction of water content; (g) Excess PVP removal by dialysis.
Figure 1. Preparation of rGO-MWCNT dispersion. (a) Preparation of GO dispersion; (b) Preparation of MWCNT; (c) Preparation of GO/MWCNT dispersion; (d) Dispersion stabilization with PVP; (e) Reduction with ascorbic acid to achieve the rGO/MWCNT dispersion; (f) Reduction of water content; (g) Excess PVP removal by dialysis.
Nanomaterials 16 00294 g001
Nanomaterials 16 00294 g002
Figure 2. Schematic representation of polymer latex preparation: (a) batch polymerization to obtain seed dispersion, (b) 2 h semi-batch polymerization of latex, finalized by 3 h in batch mode.
Figure 2. Schematic representation of polymer latex preparation: (a) batch polymerization to obtain seed dispersion, (b) 2 h semi-batch polymerization of latex, finalized by 3 h in batch mode.
Nanomaterials 16 00294 g002
Nanomaterials 16 00294 g003
Figure 3. Specimen preparation and characterization of nanomaterial filler.
Figure 3. Specimen preparation and characterization of nanomaterial filler.
Nanomaterials 16 00294 g003
Nanomaterials 16 00294 g004
Figure 4. (a) Photo of stabilized rGO/MWCNTs aqueous dispersions (10:1 (w/w) rGO: MWCNT in 100 mL water), (b) Raman spectra (Visible range) of the rGO: MWCNTs (10:1, 1:1, 1:10 (w/w)) filler platelets.
Figure 4. (a) Photo of stabilized rGO/MWCNTs aqueous dispersions (10:1 (w/w) rGO: MWCNT in 100 mL water), (b) Raman spectra (Visible range) of the rGO: MWCNTs (10:1, 1:1, 1:10 (w/w)) filler platelets.
Nanomaterials 16 00294 g004
Nanomaterials 16 00294 g005
Figure 5. TEM images of the carbon fillers in different ratios of rGO:MWCNTs fillers with the weight ratio of (a) 10:1, (b) 1:1, (c) 1:10 (w/w).
Figure 5. TEM images of the carbon fillers in different ratios of rGO:MWCNTs fillers with the weight ratio of (a) 10:1, (b) 1:1, (c) 1:10 (w/w).
Nanomaterials 16 00294 g005
Nanomaterials 16 00294 g006
Figure 6. 1—Neat Polymer; 2—0.25 wt.% rGO:MWCNT 10:1/PMMA; 3—0.5 wt.% rGO:MWCNT 10:1/PMMA; 4—1 wt.% rGO:MWCNT 10:1/PMMA; 5—1 wt.% rGO:MWCNT 1:1/PMMA; 6—1 wt.% rGO/MWCNT 1:10/PMMA.
Figure 6. 1—Neat Polymer; 2—0.25 wt.% rGO:MWCNT 10:1/PMMA; 3—0.5 wt.% rGO:MWCNT 10:1/PMMA; 4—1 wt.% rGO:MWCNT 10:1/PMMA; 5—1 wt.% rGO:MWCNT 1:1/PMMA; 6—1 wt.% rGO/MWCNT 1:10/PMMA.
Nanomaterials 16 00294 g006
Nanomaterials 16 00294 g007
Figure 7. SEM images of the cross-sectional area of composite films containing different weight ratios of rGO:MWCNTs fillers (10:1, 1:1, 1:10 (w/w)) and different loading weight percentages of the rGO:MWCNT 10:1 (w/w) sample into the polymer (0.25 wt.%, 0.50 wt.%, 1 wt.%).
Figure 7. SEM images of the cross-sectional area of composite films containing different weight ratios of rGO:MWCNTs fillers (10:1, 1:1, 1:10 (w/w)) and different loading weight percentages of the rGO:MWCNT 10:1 (w/w) sample into the polymer (0.25 wt.%, 0.50 wt.%, 1 wt.%).
Nanomaterials 16 00294 g007
Nanomaterials 16 00294 g008
Figure 8. Stress–strain curves of polymer latexes with (a) different loading ranges for 10:1 rGO:MWCNTs, and (b) increasing quantity of MWCNTs in the filler.
Figure 8. Stress–strain curves of polymer latexes with (a) different loading ranges for 10:1 rGO:MWCNTs, and (b) increasing quantity of MWCNTs in the filler.
Nanomaterials 16 00294 g008
Nanomaterials 16 00294 g009
Figure 9. Conceptual schematic of carbon-filled polymer composite demonstrating polymer–filler interfacial interactions, conductive network formation, and enhanced flexibility.
Figure 9. Conceptual schematic of carbon-filled polymer composite demonstrating polymer–filler interfacial interactions, conductive network formation, and enhanced flexibility.
Nanomaterials 16 00294 g009
Table 1. RGO/MWCNT fillers mass ratios [41].
Table 1. RGO/MWCNT fillers mass ratios [41].
rGO/MWCNTs Ratio (w/w)10:1 (w/w)1:1 (w/w)1:10 (w/w)
GO water dispersion (mL)10010010
GO solid content in water dispersion (g)0.50.50.05
MWCNT (g)0.050.50.5
Table 2. Summary of Raman results for rGO:MWCNTs (10:1, 1:1, 1:10 (w/w)) fillers and electrical conductivity of rGO-MWCNT fillers.
Table 2. Summary of Raman results for rGO:MWCNTs (10:1, 1:1, 1:10 (w/w)) fillers and electrical conductivity of rGO-MWCNT fillers.
Filler SamplesRaman ID/IGElectrical Conductivity
(Sm−1)
rGO/MWCNTs 10:1 (w/w)0.870.074
rGO/MWCNTs 1:1 (w/w)0.895.78
rGO/MWCNTs 1:10 (w/w)0.8720.84
Table 3. Summary of electrical conductivity of rGO-MWCNT composites.
Table 3. Summary of electrical conductivity of rGO-MWCNT composites.
Neat Polymer and Composite FilmsElectrical Conductivity
(Sm−1)
PMMA10−9
0.25 wt.% (rGO/MWCNTs 10:1)/PMMA2.8 × 10−5
0.5 wt.% (rGO/MWCNTs 10:1)/PMMA3.3 × 10−5
1 wt.% (rGO/MWCNTs 10:1)/PMMA2.9 × 10−5
1 wt.% (rGO/MWCNTs 1:1)/PMMA2.27 × 10−4
1 wt.% (rGO/MWCNTs 1:10)/PMMA8.2 × 10−3
Table 4. Mechanical properties of nanocomposites.
Table 4. Mechanical properties of nanocomposites.
SamplesStress
at Break (MPa)		Strain
at Break		Young’s
Modulus
(MPa)		Offset Yield Stress (MPa)Elongation at Break (%)
Neat Polymer11.8 ± 0.721.542 ± 0.210.2 ± 0.037.36 ± 0.04154 ± 21
0.25 wt.% (rGO/MWCNTs
10:1)/PMMA		12.12 ± 0.033.046 ± 0.0690.11 ± 0.013.46 ± 0.45304 ± 6.9
0.5 wt.% (rGO/MWCNTs 10:1)/PMMA11.31 ± 0.82.384 ± 0.4320.12 ± 0.023.48 ± 0.24238 ± 43.2
1 wt.% (rGO/MWCNTs 10:1)/PMMA11.32 ± 1.61.549 ± 0.2770.16 ± 0.025.25 ± 1.2154 ± 27.7
1 wt.% (rGO/MWCNTs 1:1)/PMMA12.10 ± 1.82.524 ± 0.5460.15 ± 0.023.13 ± 0.11252 ± 54.6
1 wt.% (rGO/MWCNTs 1:10)/PMMA11.82 ± 0.552.436 ± 0.1910.14 ± 0.013.64 ± 0.06243 ± 19.1
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Ehsani, M.; Prosheva, M.; Heise, K.; Gilev, J.B.; Tomovska, R.; Joseph, Y. Effects of Carbon Fillers on Electrical and Mechanical Properties of Water-Based Polymer Nanocomposites. Nanomaterials 2026, 16, 294. https://doi.org/10.3390/nano16050294

AMA Style

Ehsani M, Prosheva M, Heise K, Gilev JB, Tomovska R, Joseph Y. Effects of Carbon Fillers on Electrical and Mechanical Properties of Water-Based Polymer Nanocomposites. Nanomaterials. 2026; 16(5):294. https://doi.org/10.3390/nano16050294

Chicago/Turabian Style

Ehsani, Maryam, Marija Prosheva, Katja Heise, Jadranka Blazhevska Gilev, Radmila Tomovska, and Yvonne Joseph. 2026. "Effects of Carbon Fillers on Electrical and Mechanical Properties of Water-Based Polymer Nanocomposites" Nanomaterials 16, no. 5: 294. https://doi.org/10.3390/nano16050294

APA Style

Ehsani, M., Prosheva, M., Heise, K., Gilev, J. B., Tomovska, R., & Joseph, Y. (2026). Effects of Carbon Fillers on Electrical and Mechanical Properties of Water-Based Polymer Nanocomposites. Nanomaterials, 16(5), 294. https://doi.org/10.3390/nano16050294

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop