Nanocomposites Prepared by Incorporation of Surface Functionalized CeO₂ Nanoparticles in PMMA Matrix

Abstract

In this work, CeO₂ nanoparticles were synthesized via the chemical precipitation method. With this objective, two distinct surface functionalization methodologies were applied: the first one uses anionic surfactant (SDS), and the second one uses hexadecanoic acid (C₁₆H₃₂O₂). During the development of this work, nanostructured films were obtained via direct mixing and the solvent evaporation method (in situ and ex situ). This material was characterized via thermogravimetry (TGA), differential scanning calorimetry (DSC), field emission gun scanning electron microscopy (FEG-SEM), infrared absorption spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD). By XRD, when there is adequate incorporation and dispersion of nanoparticles, the characteristic peaks of the CeO₂ crystalline planes are observed in the nanocomposites, and by SEM, their microstructures are evaluated to verify the dispersion. The results obtained showed that the synthesis protocols tested for the intended nanocomposite, with in situ or ex situ functionalization, were satisfactory. According to these results, it was possible to observe the agglomeration of nanoparticles without functionalization and confirm the nanometric scale for CeO₂ nanoparticles synthesized without functionalization and with in situ functionalization (SDS), and their diameters were between approximately 10 and 15 nm. Additionally, for the PMMA powder, the T_g was 114 °C, whereas for the nanocomposite films, it averaged 53 °C, suggesting that the solvent acts as a plasticizing agent in the studied samples, thus reducing the T_g value. However, when samples obtained from the ex situ protocol by phase transfer with palmitic acid were analyzed, uncertainties were found regarding the adequate dispersion of CeO₂ nanoparticles in PMMA, with in situ functionalization by SDS being the most promising.

Keywords:
Nanocomposite; PMMA; CeO₂; Surface Functionalization; Phase Transfer; Functional Coating

1. Introduction

In the last few years, many different materials have created a new generation of materials for the future¹-³. Currently, nanocomposite materials represent new alternatives to overcome the application limitations of conventional materials, becoming materials of the near future, mainly owing to their advantages, such as high surface/volume ratios; good mechanical, thermal and electrical properties; and improved optical properties¹-³. Inside this context, nanocomposite-functionalized coatings are the focus of several technological studies and developments, as they can present exclusive physical and chemical properties once selected nanoparticles can improve polymeric matrix properties⁴,⁵.

Nanocomposite materials stand out because of their excellent physicochemical properties, which arise from the synergy of their constituents. Owing to these properties, these materials have been widely used in various applications, such as dielectric ceramics, electrochromic devices, biosensors, corrosion protection, supercapacitors and optoelectronic devices, among others⁶-¹⁰.

Currently, industries in the offshore¹¹, automotive and aerospace¹² areas are interested in coatings involving acrylic nanocomposites, since these materials allow the production of artifacts with excellent properties involving low electrolyte permeation, strong adhesion to the substrate, thermal stability, mechanical resistance and high durability in aggressive environments¹³. In this context, the use of cerium-based compounds as a complement to organic‒inorganic hybrid materials has gained prominence, especially when anticorrosive coatings are used to prevent the access of aggressive species to the metallic interface of these components, owing to the cathodic protection generated by the presence of Ce³⁺ and Ce⁴⁺ ions¹¹.

Among the available synthesis methods, such as hydrothermal, glycothermal, pyrolysis and precipitation methods, routes in solution are relatively low cost and easy to perform. The solution routes for cerium oxide (CeO₂) synthesis have the advantage of controlling the size of the particles formed and are promising for the preparation of nanometric particles, in which the degree of agglomeration is significantly reduced because of the absence of extensive heat treatment¹⁴-¹⁶. Since the properties of dispersed particles less than 10 nm in diameter are governed by the quantum size effect, these properties are behind many applications of ceria¹⁴,¹⁷,¹⁸.

CeO₂ NPs are characterized for their transparency in the visible region, with a refractive index of 2.2 at a wavelength of 632 nm. All these properties allow several applications for these nanocomposites, such as optical devices, solar cells, oxidation catalysis in fuels, antioxidant systems and several medical applications¹⁹-²⁶.

In accordance with what was presented previously, the authors of this work consider the following results: optical properties, such as diffuse reflectance and Tauc’s plot of PMMA and PMMA/CeO₂ nanocomposites; variation in the refractive index; real and imaginary parts of the optical permittivity (εʹ) and optical dielectric loss tangent (tan δ) of the PMMA and PMMA/CeO₂ nanocomposites; dielectric studies of the PMMA and PMMA/CeO₂ nanocomposites; and antimicrobial and antibiofilm studies of the PMMA and PMMA/CeO₂ nanocomposites, which are of great interest in this area. However, this article will not address these points specifically since the objective of this publication is to characterize this material via thermogravimetry (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), infrared absorption spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD).

Polymerization with inorganic nanoparticles with modified surfaces can be performed through dispersion, suspension, and emulsion processes to form hybrid nanocomposites. Several synthesis parameters may influence the homogenization process for the formation of nanostructured composites²⁷,²⁸. Among these, the knowledge and control of the interaction between acrylic monomers and organic additives is highly important. Studies involving the coupling of molecules with inorganic groups linked to acrylic groups have been carried out to better understand the establishment of covalent bonds between these constituents, which can generate crosslinking in the structure. As a result of this interaction, these molecules improve the adhesion between the nanocomposite and the metal substrate since they prevent the aggregation of inorganic particles and generate covalent bonds between the silane groups and hydroxyl bonds²⁸,²⁹.

In this work, the main objective was to develop nanocomposite films based on a polymethyl methacrylate (PMMA) polymeric matrix filled with surface-modified cerium oxide nanoparticles. CeO₂ nanoparticles were synthesized via a chemical precipitation route, and their surface functional groups, crystallinity, and morphology were characterized. The behavior of the PMMA/CeO₂ nanocomposites was characterized via spectroscopic techniques, as their morphological and thermal stabilities were compared among the different samples produced, considering the nanoparticle functionalization protocols used.

2. Methodology

In this work, CeO₂ nanoparticles were synthesized via chemical precipitation, a widely adopted method due to its cost efficiency and reproducibility. Surface functionalization was performed via two distinct strategies: (i) in situ functionalization, where the surfactant was introduced during nanoparticle synthesis, and (ii) ex situ functionalization, where surfactant modification occurred postsynthesis¹².

For in situ functionalization, sodium dodecyl sulfate (SDS; C₁₂H₂₅SO₄Na) was selected as the anionic surfactant owing to its affordability and commercial availability. For ex situ functionalization, palmitic acid (PA; C₁₆H₃₂O₂) was employed; its long hydrocarbon chain promotes colloidal stability in organic solvents, whereas the terminal carboxylate group facilitates surface modification³⁰-³³.

PMMA/CeO₂ nanocomposites were prepared by dispersing functionalized nanoparticles into PMMA dissolved in an appropriate solvent. The mixture was magnetically stirred for 48 h at room temperature until complete solvent evaporation, yielding homogeneous PMMA/CeO₂ composite films.

2.1. Reagents, materials and equipment

The following high-purity reagents were employed without further purification: cerium precursor: cerium(III) nitrate hexahydrate (Ce(NO₃)₃·6H₂O, 99%, Sigma‒Aldrich); precipitation reagent: ammonium hydroxide solution (NH₄OH, 28–30% w/w, Êxodo Científica); surfactant: sodium dodecyl sulfate (SDS, C₁₂H₂₅NaO₄S, 95%, Êxodo Científica) for in situ functionalization; palmitic acid (PA; C₁₆H₃₂O₂, 99.5%, Neon) for ex situ modification; solvent: chloroform (CHCl₃, 99.8%, ACS Científica) for polymer dissolution; and polymer matrix: commercial polymethyl methacrylate (PMMA, Acrigel ECL®) provided by Unigel Plásticos S.A.

2.2. CeO₂ nanoparticle (in situ functionalized) synthesis

The functionalized nanoparticles were prepared through an aqueous precipitation route with concurrent surfactant stabilization. The precursor dissolution stage: A cerium source solution was prepared by dissolving 2.17 g of Ce(NO₃)₃·6H₂O in 50 mL of deionized water under constant magnetic stirring until complete homogenization. Surfactant incorporation: The clear cerium solution was then mixed with 50 mL of an aqueous SDS solution (0.05 M) as a stabilizing agent. The mixture was stirred to allow precomplexation of cerium ions with the anionic surfactant. Precipitation and aging: Nanoparticle formation was initiated by the dropwise addition of 25 mL of NH₄OH (1.0 M) as a precipitating agent, following alkaline hydrolysis principles reported in prior work³⁴. The pH value was verified using pH-indicator strips, and all measurements were greater than 10. The resulting colloidal suspension was aged for 1 h to ensure complete particle growth. Purification and processing: The CeO₂ NP_SDS precipitate was isolated by centrifugation (3,000 rpm), followed by three washing cycles with deionized water to remove ionic residues. The purified product was oven-dried (80 °C, 12 h) and mechanically homogenized via an agate mortar to obtain free-flowing powder.

2.3. PMMA/CeO₂ (in situ functionalized) nanocomposite synthesis – NC-01

The synthesis of PMMA/CeO₂ via the in situ method was initially carried out by solubilizing the polymer in powder form (as received) in the best-tested solvent, CHCl₃, at a proportion of 10% (w/v). This reaction medium was maintained under slow magnetic stirring for 24 h to allow the formation of a highly homogeneous, bubble-free matrix prior to the addition of ceria nanoparticles. The incorporation of CeO₂ NP_SDS (2 wt%) was carried out by direct mixing of the solid nanoparticles (section 2.3) with the PMMA solution, followed by magnetic stirring for 4 h to ensure homogeneous dispersion. The obtained product was dispersed in a mold for casting and left to dry at room temperature for 48 h to obtain the nanocomposite film.

2.4. PMMA/CeO₂ (ex situ functionalized) nanocomposite synthesis – NC-02

The ex situ method for obtaining functionalized nanoparticles was carried out via the phase transfer methodology, taking advantage of the good interaction between the carbon chain of palmitic acid (PA) and the solvent. The method consists of (i) chemical precipitation; (ii) surface functionalization (ex situ); (iii) phase transfer; (iv) phase separation; (v) preparation of the polymer matrix; and (vi) incorporation of the nanoparticles.

The precursor dissolution and chemical precipitation steps were carried out in the same manner as that adopted for the in situ functionalization protocol. Briefly, 20 mL of Ce(NO₃)₃·6H₂O solution was prepared by dissolving 2.17 g in deionized water until complete homogenization. The solution was then added to 25 mL of NH₄OH (1 mol/L – pH > 10) and initially stirred with a glass rod for a few minutes. Subsequently, the mixture was heated to 80 °C and magnetically stirred for 50 min.

Surface functionalization (ex situ): Thereafter, 0.05 g of PA (3,75% mol/%) was added, and the mixture was stirred and heated for another 1 h. After that, the heat stopped and the mixture was cooled to room temperature under stirring. The mixture was then filtered to eliminate excess particulate material.

Phase transfer: 20 mL of chloroform was added (10% w/v), and magnetic stirring was resumed. Thus, owing to intermolecular forces, the functionalized nanoparticles should migrate to the organic phase. This process was experimentally monitored by light dispersion (Tyndall effect), a phenomenon in which light is scattered by colloidal or suspended particles, making the light beam visible as it passes through the suspension.

The phase transfer step, or liquid–liquid extraction—a separation process in which solutes are transferred between two immiscible liquid phases, typically aqueous and organic, based on the differential solubility of the target analyte—is essential for the incorporation of CeO₂ into intrinsically hydrophobic PMMA. Phase separation: The organic phase, containing the functionalized nanoparticles after phase transfer, was collected using a separatory funnel.

Preparation of the polymer matrix: The polymer matrix was prepared as previously described in Section 2.3. PMMA was dissolved in chloroform and maintained under magnetic stirring for 24 h. Incorporation of the nanoparticles: However, in this protocol, the previously collected chloroform aliquot was added to the PMMA/CHCl₃ solution under magnetic stirring for an additional 3 h. After this period, the mixture was transferred to a mold for solvent elimination and dried at room temperature for 48 hours to obtain a 2% (w/w) nanocomposite film.

2.5. Characterization

The following techniques were used for the characterization of CeO₂ NPs: Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray powder diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM) were performed for some produced samples. To characterize the PMMA/CeO₂ NP_SDS nanocomposites, FTIR, XRD, thermogravimetry (TGA/DTG), differential scanning calorimetry (DSC) and SEM analyses were performed on commercial and PMMA nanocomposites.

The infrared spectroscopy was run on a Spectrum 100 ATR FTIR spectrophotometer (PerkinElmer, Inc., United States) using an ATR accessory with germanium crystals. The FTIR spectra were recorded with 16 scans per spectrum and a resolution of 4 cm^-1.

The Raman spectra were obtained via a Horiba LabRam HR Evolution confocal spectrophotometer (Horiba, Ltd., Japan), featuring a spectral resolution of 2 cm^-1, an argon laser (λ = 514.5 nm), at room temperature, with a power of 10 mW.

The XRD powder patterns were obtained by using a Philips X’Pert MRD high-resolution diffractometer for nanoparticles (Philips Analytical, The Netherlands) as well as Bruker D8 Advance (Bruker Co., United States) for nanocomposites, in both cases employing Cu Kα radiation (λ = 1.5406 Å) and setting 40 kV and 20 mA.

Field emission scanning electron microscopy (SEM) was performed on a model MIRA 3 FEG-SEM (TESCAN USA, Inc. United States) using a 5 kV beam voltage. Images from transmission electron microscopy (TEM) were captured via a JEOL JEM-2100 microscope equipped with an energy-dispersive X-ray (EDS) spectrometer (JEOL Ltd., Japan) using an accelerating voltage of 200 kV.

The aggregate size analysis was performed using ImageJ by measuring at least 80 individual aggregates from representative microscopy images. The aggregate diameters were obtained using an ellipsoidal fitting approach, and the values reported correspond to the mean diameter calculated from these measurements.

TGA‒DTG curves were obtained via a SEIKO EXSTAR instrument, model TG/DTA 6200 (SII NanoTechnology Inc., Japan). The parameters used were as follows: flow rate of 100 mL min^-1 for both purge gas atmospheres (synthetic dry air and N₂); heating rate of 10 °C min^-1 for all analyses; and sample mass of approximately 10 mg in an alumina crucible.

The DSC Q20 module (TA Instruments Co., United States) was used to record the DSC curves. The purge gas used was N₂ with a flow rate of 40 mL min^-1. The heating rate was 10 °C min^-1, and the sample mass was approximately 10 mg. The heating cycles were carried out in the temperature range between 0 and 125 °C. Aluminum crucibles with perforated lids in the center were employed during the analysis.

3. Results and Discussions

3.1. CeO₂ nanoparticles

3.1.1. FTIR and Raman spectroscopy

The infrared spectroscopic spectrum of the CeO₂ NPs with no functionalization is presented in Figure 1a. A broad band in the range of 3349 cm^-1 can be attributed to the stretching vibration of the O–H bond in the OH groups from residual water and the hydroxylic groups generated by the synthesis process. In their studies on the properties of CeO₂ NPs, Jayakumar et al.³⁴ attributed the band observed at 1630 cm^-1 to the OH vibration mode of water molecules. They emphasized that for any synthesis method in an aqueous solution, there will always be residual water molecules and OH groups on the CeO₂ NPs, which will be detected via FTIR spectroscopy.

Figure 1
CeO₂ nanoparticles: a) FTIR spectrum and b) Raman spectrum.

The absorption peaks at 1325 and 1509 cm⁻¹ can also be attributed to physically adsorbed water molecules. The bands located at approximately 1048 cm^-1 can be related to C–O stretching. These bands are due to atmospheric carbon dioxide since cerium oxide readily absorbs atmospheric water and air. The FTIR spectra presented absorption peaks at 880 cm⁻¹ and 650 cm^-1, which are typical peaks of Ce–O bond stretching vibrations³⁴-³⁶.

Ramachandran et al.³⁶ reported the influence of pH on the synthesis and characterization of cerium oxide nanoparticles and observed that the band around 2300 cm^-1, associated with the C=O stretching vibration, appears only when the nanoparticles are obtained at pH values below 10. As shown in Figure 1a, this band is not observed, indicating that the reaction medium had a pH above 10. In contrast, the band at 880 cm^-1 is assigned to a Ce–O stretching, which is characteristic of cubic CeO₂.

Therefore, to complement the FTIR analysis, RAMAN spectroscopy analysis was performed, according to the results presented in Figure 1b. The results obtained from the Raman spectrum clearly revealed the characteristic band corresponding to the elongation vibration of the Ce-O bond at approximately 466 cm^-1, similar to that reported in the literature³⁴,³⁷.

3.1.2. X-ray diffraction (XRD) patterns

XRD analyses were used to qualitatively evaluate the peak positions corresponding to the respective planes in the crystalline structure in the spectra of the CeO₂ NPs and CeO₂ NP_SDS (Figure 2). The sample diffractograms were indexed according to ICSD form 01-081-0792 as CeO₂, a cubic crystalline system, with network parameters a = b = c = 5.4124 Å and space group Fm-3 m. Well-defined and narrow peaks can be observed, which indicate the good crystallinity of the samples.

Figure 2
CeO₂ nanoparticle diffractograms.

The size of the crystallites (d) can be obtained via the Scherrer equation (presented in Equation 1), in which λ is the wavelength of the incident X-ray (0.15406 nm); θ is the angle of incidence of the X-ray; β is the FWHM (full width half maximum); and k is the Scherrer constant with an approximate value of 0.94. CeO₂ NPs had crystallite sizes of approximately 14.8 nm, and CeO₂ NP_SDS had crystallite sizes of approximately 12.7 nm³⁸.

$D=\frac{K}{\cos \theta }$ (1)

In the in situ functionalization protocol, nanoparticle formation and surface modification occur simultaneously. This approach is primarily employed to overcome the inherent instability of freshly synthesized nanoparticles, which are prone to rapid agglomeration and oxidation. As a result, this procedure generally yields smaller nanoparticles due to factors such as growth inhibition associated with reduced nucleation activity and adsorption onto developing nanocrystals. Furthermore, surface functionalization provides a protective layer that mitigates the effects of the high surface-area-to-volume ratio and magnetic attraction forces that typically lead to particle aggregation, thereby enhancing system stability.

3.1.3. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

Scanning electron microscopy (SEM) was used to verify the morphology of the CeO₂ nanoparticles synthesized without functionalization, as presented in Figure 3, where there was significant agglomeration.

Figure 3
SEM images of CeO₂ NP microstructures (SEM) with magnifications of (a) 7,92 kx and (b) 19,1 kx. TEM images of CeO₂ NPs (c) 20 nm, (d) 10 nm scale, and CeO₂ NP_SDS (e) 20 nm, and (f) 10 nm scale.

Microstructures are essentially formed by the agglomeration of smaller particles with irregular shapes and contours. It is possible to observe the formation of gaps between the clusters, which gives rise to a highly porous structure. According to Zheng and collaborators³⁹, these pores provide access to the internal part of the structure, enabling them to act as effective transport pathways. Additionally, the porous structure associated with the crystal facets significantly increases the surface area of the sample.

Furthermore, consistent with previous studies by Wang et al.⁴⁰, the micrographs reveal a wide particle size distribution, with agglomerates of smaller particles exhibiting irregular shapes and sizes.

Transmission electron microscopy (TEM), which is typically used for the characterization of materials at the nanoscale, was used to verify the morphology of the synthesized CeO₂ NPs and CeO₂ NP_SDS, according to the images presented in Figures 3cf.

For both the micrographs obtained for CeO₂ NPs and CeO₂ NP_SDS, their diameters were in the range of 10–15 nm, and no significant difference in size was observed. The observed nanoparticle diameters confirmed the results obtained by calculating the crystallite sizes via X-ray diffraction (XRD) (14.8 nm for CeO₂ NPs and 12.7 nm for CeO₂ NP_SDS). These results are in accordance with those of Parlak and Demir⁴¹. This finding is similar to the results presented by Wang and Feng¹⁶, who reported a textured distribution of nanoparticles deposited on a substrate surface with a preferential orientation.

The micrographs of CeO₂ NP_SDS have a more regular and orderly format than nanoparticles without functionalization, which indicates that the surfactant has a relevant ability to homogenize the morphology of the nanoparticles. This fact is corroborated by Paschalidou and Theocharis⁴² who reported that surfactants have the ability to involve nanoparticles, favoring the formation of specific phases and determining the shape of particles and their surface properties.

3.2. PMMA/CeO₂ NPs

The FTIR results obtained for the characterization of the PMMA/CeO₂ nanocomposite samples are presented in Figure 4 and are compared with the results obtained for a pure PMMA film. NC-01 is functionalized in situ (SDS surfactant), and NC-02 is functionalized ex situ (palmitic acid). It is possible to compare the spectra of the films obtained with the respective functionalizing reagents and the functionalized nanoparticles obtained via in situ (SDS) and ex situ (PA) procedures.

Figure 4
Comparison of the FTIR spectra of (a) PMMA, (b) NC-01, (c) CeO₂ NP_SDS, (d) SDS, (e) NC-02, (f) CeO₂ NP and (g) PA.

For PMMA (Fig. 4a), according to the literature⁴³, there is a distinct absorption range between 1150 cm^-1 and 1250 cm^-1, which can be attributed to the C-O-C stretching vibration. The band at 1732 cm^-1 corresponds to the presence of the carbonyl acrylate group. The two bands at 2997 cm^-1 and 2952 cm^-1 can be attributed to the stretching vibrations of the C‒H bonds of the -CH₃ and -CH₂ groups, respectively. The signal at 754 cm^-1 can be attributed to the vibrations of the α-methyl group.

Due to the small amount of incorporated NPs and the strong intensity of the PMMA polymer matrix peaks, the characteristic peaks of CeO₂ were suppressed and are not distinguishable. However, for NC-01 presented in Fig. 4b, the characteristic bands of the SDS surfactant used in nanoparticle functionalization became evident. Absorptions such as those located at 2849 cm^-1 and 2917 cm^-1 are related to aliphatic -C-H stretching frequencies; those at 1216 cm^-1 are due to -S=O stretching; peaks originating from the -S-O-C group at 993 cm^-1 and 828 cm^-1; and bands at 1468 cm^-1, 1377 cm^-1 and 721 cm^-1 refer to -C-H bending of methyl and methylene groups. Finally, the band at 1081 cm^-1 represents the characteristic vibration of the SO₄^2- Group³⁵-³⁹. Therefore, this confirms the incorporation of CeO₂ NP-SDS into the polymer matrix.

As shown in Fig. 4e, the spectrum of PA-functionalized sample (NC-02) indicates that functionalization with PA was clearly less effective than with SDS. Only a weak signal corresponding to the band at 2847 cm⁻¹, assigned to the symmetric stretching vibration of –CH₂, and a slight shift of the band at 1719 cm⁻¹, compared to those at 1732 cm⁻¹ for PMMA and 1699 cm⁻¹ for PA—both associated with the respective carbonyl groups—are observed. For both nanocomposites, the characteristic PMMA bands are clearly visible.

The nanoparticle X-ray diffraction patterns (Figure 5) were indexed as CeO₂ based on the ICSD card No. 01-081-0792.

Figure 5
PMMA, nanocomposites and CeO₂ nanoparticle diffractograms.

Only the NC-01 diffractogram, with CeO₂ NP_SDS, presented peaks related to cerium oxide, suggesting the effective incorporation of the nanoparticles in the polymer (PMMA). In the NC-02 diffractogram, the peaks could not be well defined, which indicates that there were problems in the incorporation and/or dispersion of the nanoparticles in this sample. The NC-02 diffractogram has a similar profile as that of PMMA, which is characteristic of amorphous solids.

However, as reported by Parlak and Demir⁴¹, when the amorphous characteristic of PMMA stands out in relation to CeO₂ peaks, the sample diffractogram has a smoother profile, which in fact occurs with the NC-02 diffractogram. In addition, the percentage of nanoparticles incorporated into the polymer matrix can be considered too low to be identified only by XRD.

For the TGA/DTG analyses, the atmosphere was varied, and the thermogravimetric curves obtained are presented in Figure 6a for the synthetic air atmosphere and Figure 6b for the N₂ atmosphere.

Figure 6
TG‒DTG curves of the PMMA, NC-01 and NC-02 nanocomposites in (a) a synthetic air atmosphere and (b) a N₂ atmosphere.

From the TGA/DTG curves presented in Figures 66b, at least two stages of thermal decomposition were identified for the PMMA film. The literature⁴⁴-⁴⁷ also reported the presence of 2 stages of thermal decomposition for PMMA, and they divided the first stage into two stages, as can be observed by the inflection of the curve at this stage.

The first stage of thermal decomposition of PMMA occurred at approximately T_1onset = 119 °C and resulted in a mass loss (Δm₁) of 17.51%. The second stage of thermal decomposition showed variation in the start temperature (T_2onset) between 286 and 336 °C, but this resulted in a mass loss (Δm₂) of 81.80% for the analyzed samples.

According to the Zheng et al.³⁹, the thermal decomposition of PMMA is a process characterized by high monomer yields in the products of degradation and a slow decrease in the molar mass of the polymer. This characteristic explains why the main stage of degradation presented a mass loss greater than 80% when the C‒C bonds were split, which are the most stable bonds in the PMMA structure.

Additionally, from the TGA/DTG curves presented in Figures 66b, it is possible to observe that the PMMA/CeO₂ nanocomposites maintain the same thermal behavior as the pure PMMA film, in which two stages of thermal decomposition of the material are identified.

In general, in a synthetic air atmosphere, the first stage of decomposition for the PMMA/CeO₂ nanocomposites occurred at approximately 118 °C (T_1onset) and resulted in an average mass loss (Δm₁) of 19%, similar to that of the pure PMMA film (T_1onset = 119 °C; Δm₁ = 19%). The second thermal event showed a small variation in the starting temperature for NC01 (increase of 5%, starting at 286 °C), with an average mass loss (Δm₂) of 79%, which was also similar to that of the pure PMMA film (Δm₂ = 79%).

At 500 °C, the percentages of residues obtained in a synthetic air atmosphere for the pure PMMA and NC-02 films were very similar, which may indicate problems in the dispersion of nanoparticles in the synthesis protocol with functionalization with palmitic acid. For NC-01, an increase of 2.8 times the residue mass was obtained compared with that of the pure PMMA film, which indicates the effective presence of CeO₂ nanoparticles.

In a nitrogen atmosphere, the first thermal event for the PMMA/CeO₂ nanocomposites started at approximately 122 °C (T_1onset) and resulted in an average mass loss (Δm₁) of 17%, similar to that of the pure PMMA film (T_1onset = 122 °C; Δm1 = 17%). The second stage of decomposition was maintained at approximately 331 °C (T_1onset) and resulted in a mean mass loss (Δm₂) of 83% for the samples of the nanocomposites analyzed, which was also similar to that of the pure PMMA film (T_2onset = 327 °C; Δm₂ = 83%).

At 500 °C, the percentage of residue obtained in a nitrogen atmosphere for the pure PMMA film of only 0.14% is probably due to impurities or mild contamination during the handling of the PMMA powder or during solvent solubilization of the film. On the other hand, the percentages of residues in the nanocomposites are significantly greater than those in the pure PMMA film: 11.8 times greater for NC-01 (1.65%) and 6.3 times greater for NC-02 (0.88%). This finding indicates the effective presence of CeO₂ nanoparticles in the nanocomposites and suggests that the synthesis protocol for NC-01 probably provides better dispersion of CeO₂ nanoparticles in the PMMA matrix than the NC-02 synthesis protocol does.

From the previous results, there is also a small influence of in situ functionalization with SDS at the beginning of the second stage of decomposition, corresponding to an increase of 5% in the temperature in a synthetic air atmosphere and 3% in a nitrogen atmosphere, compared to the beginning for the pure PMMA film sample.

The highest percentage of residue at 500 °C was obtained for the nanocomposite films in relation to the pure PMMA film, indicating that CeO₂ nanoparticles were incorporated into the PMMA matrix.

The DSC curves are shown in Figure 7. In all the DSC curves, a characteristic glass transition event was observed. The occurrence of a single T_g was observed in each sample, and the melting phenomenon was not observed, which indicates that the sample material was amorphous. Moreover, there is an inflection point in the curves below the T_g between approximately 50 and 60 °C for the films and 120 °C for the powder, indicating that the thermal stress and enthalpic relaxation are associated with the T_g of the samples.

Figure 7
DSC curves of the PMMA powder (a), PMMA film (b), NC-01 (c) and NC-02 (d) nanocomposites in a N₂ atmosphere.

The glass transition temperatures (onset) and the corresponding standard deviations for the nanocomposites, PMMA powder, and PMMA film were 43.4 ± 0.2 °C (NC-01), 43.7 ± 0.3 °C (NC-02), 111.4 ± 0.3 °C (powder), and 54.1 ± 0.4 °C (film), respectively. All DSC measurements were performed in triplicate, and the values reported correspond to mean values. According to the manufacturer’s specifications, the experimental uncertainty of the DSC equipment is in the range of 1-2 °C; therefore, the small differences observed among the T_g onset values for the nanocomposites should be interpreted with caution, as they fall within the instrumental uncertainty of the technique.

The main difference observed in the DSC results was between the T_g values for the powder and PMMA films, which suggests that the solvent used during film formation may influence the thermal properties of the material. For the PMMA powder, the T_g was 111.4 °C, whereas for the nanocomposite films, it averaged 43 °C, suggesting that the solvent acts as a plasticizing agent in the studied samples, thus reducing the T_g value. From the DSC curves presented in Figure 7, the PMMA/CeO₂ nanocomposites exhibit thermal behavior similar to that of the pure PMMA film, characterized by a deviation from the baseline in the endothermic direction, associated with the T_g, followed by an enthalpic relaxation attributed to thermal stress.

A slight trend in T_g variation was observed regardless of the nanoparticle functionalization method. Specifically, in situ functionalization with SDS yielded marginally higher T_g values, while ex situ functionalization with palmitic acid resulted in slightly lower values. These results demonstrate that the functionalization route does not exert a significant influence on the glass transition behavior of the nanocomposites.

In the present study, the observed decrease in the glass transition temperature is primarily attributed to the plasticizing effect of residual CHCl₃ used during PMMA solubilization. Eriksson et al.⁴⁸ demonstrated that solvent-polymer interactions play a decisive role in T_g shifts, specifically, the acidic nature of chloroform promotes strong interactions with the basic sites of PMMA, hindering complete solvent removal even after drying.

This is a critical observation, as several reports in the literature attribute Tg depressions to nanoparticle-induced mobility changes, when they may, in fact, be experimental artifacts stemming from solvent retention. This interpretation is consistent with studies on rigid nanostructures where the intrinsic effect of the filler on Tg is expected to be negligible, further pointing to the processing solvent as the dominant factor. In addition, due to the small amount of NPs added, their impact on T_g may be minimal or even nonexistent⁴⁸,⁴⁹.

3.2.1. Scanning electron microscopy (SEM)

From the images obtained, by contrast and differentiated shape (possibly a cluster of spheres) in relation to the polymer matrix, it was observed that CeO₂ nanoparticles are effectively present in the nanocomposites (NC-01 and NC-02), with a distribution similar to that obtained in studies in the literature⁵⁰-⁵⁶. The dispersion of the nanoparticles in the matrix was heterogeneous, and agglomeration points were observed at greater magnifications (25.0 kx and 50.0 kx). These nanoparticle agglomeration points were more prominent in NC-02, reaching approximately 400 nm, which was probably influenced by the parameters of their synthesis process, such as the type of surfactant, temperature, number of reagents, time and direct mixing speed. In NC01, the agglomeration points were smaller, up to approximately 200 nm.

Although the dispersion was heterogeneous, it is possible to recognize nanoparticles throughout the analyzed area of the samples of all the nanocomposites, which indicates that there was no preferential concentration in a given region or that the nanoparticles were completely clustered, which allowed them to spread through the structure of the polymer matrix, changing the texture of the analyzed surface.

Notably, although the diffractogram of NC-02 (depicted in Figure 5) did not indicate the presence of peaks related to CeO₂, it was possible to effectively verify the presence of nanoparticles in the micrographs in Figure 8. This fact confirms that XRD is not a fully adequate technique for evaluating the incorporation of low-concentration nanoparticles in the polymer matrix used and that, in these situations, other techniques should be used to obtain the correct characterization.

Figure 8
SEM micrographs of PMMA-based films: (a,b) neat PMMA at magnifications of 1.00 kx and 25.0 kx, respectively; (c,d) NC-01 film at 1.00 kx and 25.0 kx; (e,f) NC-02 film at 1.00 kx and 25.0 kx.

In general, the micrographs in Figure 8 verify that the morphology of the structure of the obtained PMMA/CeO₂ nanocomposites is irregular and presents pores, such as the structure of the pure PMMA film used in this work. The porosity of the structure may be related to both the raw materials and the parameters of the synthesis process, such as the time, speed, stirring temperature, and solvent used, which can be adjusted to enable a more regular morphology.

4. Conclusions

This work investigated the synthesis of PMMA/CeO₂ nanocomposites using a commercially available PMMA matrix and CeO₂ nanoparticles obtained via in situ and ex situ functionalization routes. The study focused on comparing the synthesis protocols and assessing their influence on nanoparticle dispersion, structural features, and thermal behavior, providing a fundamental basis for the development of polymer-based nanocomposites with potential relevance for future applications.

Microscopy analyses revealed pronounced nanoparticle agglomeration in the absence of surface functionalization, while nanometric CeO₂ particles with diameters of approximately 10–15 nm were observed for both non-functionalized and in situ functionalized (SDS) samples. FTIR, XRD, and SEM results confirmed the successful incorporation of CeO₂ nanoparticles into the PMMA matrix. The PMMA/CeO₂ nanocomposite films exhibited thermal behavior similar to that of the pure PMMA film, indicating that the incorporation of nanoparticles did not significantly alter the characteristic features of the polymer matrix.

The results demonstrate that the slight variation in the glass transition temperature of the nanocomposites is predominantly influenced by solvent-polymer interactions from the film-casting process. The choice of nanoparticle functionalization route showed a negligible effect on T_g, suggesting that both methods preserve the same thermomechanical behavior of the polymer matrix. In general, both the nanocomposite films and the pure PMMA film exhibited irregular and porous structures.

Although the synthesis route influenced nanoparticle dispersion and interfacial characteristics, the present study did not evaluate functional properties associated with coating performance. Therefore, no definitive conclusions can be drawn regarding the superiority of one functionalization method over another in terms of final application performance. Future studies addressing specific functional properties—such as barrier behavior, corrosion resistance, mechanical performance, or durability—are required to establish the suitability of these nanocomposites for coating applications and to determine which synthesis route is more appropriate for a given application.

5. Acknowledgments

The authors are grateful for the financial support given by the Brazilian Funding Institutions: São Paulo Foundation Research (FAPESP) (2017/16970-0; 2017/04740-0, 2018/07867-3, and 2019/18691-6) and the National Council for Scientific and Technological Development (CNPq) (140852/2018-2, 306576/2020-1 and 304876/2020-8), and this study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) Finance Code 001. Special thanks to Laboratório Multiusuário de Microscopia de Alta Resolução (LabMic/UFG) for the TEM analysis and Laboratório Associado de Sensores e Materiais (LAS) - Instituto Nacional de Pesquisas Espaciais (INPE) for the FEG-SEM analysis.

6. Data Availability

The data utilized to buttress the conclusions of this study are available from the corresponding author upon request.

7. References

• ¹ Di Benedetto RM, Botelho EC, Janotti A, Ancelotti AC Jr, Gomes GF. Development of an artificial neural network for predicting energy absorption capability of thermoplastic commingled composites. Compos Struct. 2021;257:113131. https://doi.org/10.1016/j.compstruct.2020.113131
  » https://doi.org/10.1016/j.compstruct.2020.113131
• ² Batista NL, Rezende MC, Botelho EC. Effect of crystallinity on CF/PPS performance under weather exposure: Moisture, salt fog and UV radiation. Polym Degrad Stabil. 2018;153:255-61. https://doi.org/10.1016/j.polymdegradstab.2018.03.008
  » https://doi.org/10.1016/j.polymdegradstab.2018.03.008
• ³ Botelho EC, Nogueira CL, Rezende MC. Monitoring of nylon 6,6/carbon fiber composites processing by X-ray diffraction and thermal analysis. J Appl Polym Sci. 2002;86(12):3114-9. https://doi.org/10.1002/app.11335
  » https://doi.org/10.1002/app.11335
• ⁴ Zhang S, Sun D, Fu Y, Du H. Recent advances of superhard nanocomposite coatings: a review. Surf Coat Tech. 2003;167(2-3):113-9. https://doi.org/10.1016/S0257-8972(02)00903-9
  » https://doi.org/10.1016/S0257-8972(02)00903-9
• ⁵ Khan AA, Paquiza L. Synthesis and characterization of in situ polymerized poly(methyl methacrylate)-cerium molybdate nanocomposite for electroanalytical application. J Appl Polym Sci. 2013;127(5):3737-48. https://doi.org/10.1002/app.37672
  » https://doi.org/10.1002/app.37672
• ⁶ Jayakrishnan P, Ramesan MT. Studies on the effect of magnetite nanoparticles on magnetic, mechanical, thermal, temperature dependent electrical resistivity and DC conductivity modeling of poly (vinyl alcohol-co-acrylic acid)/Fe₃O₄ nanocomposites. Mater Chem Phys. 2017;186:513-22. https://doi.org/10.1016/j.matchemphys.2016.11.028
  » https://doi.org/10.1016/j.matchemphys.2016.11.028
• ⁷ Kim H, Miura Y, Macosko CW. Graphene/polyurethane nanocomposites for improved gas barrier and electrical conductivity. Chem Mater. 2010;22(11):3441-50.
• ⁸ Madhan Kumar A, Gasem ZM. Effect of functionalization of carbon nanotubes on mechanical and electrochemical behavior of polyaniline nanocomposite coatings. Surf Coat Tech. 2015;276:416-23. https://doi.org/10.1016/j.surfcoat.2015.06.036
  » https://doi.org/10.1016/j.surfcoat.2015.06.036
• ⁹ Moustafa H, Darwish NA, Youssef AM, Reda SM, El-Wakil AEAA. High-performance of nanoparticles and their effects on the mechanical, thermal stability and UV-shielding properties of PMMA nanocomposites. Egypt J Chem. 2018;61(1):23-32. https://doi.org/10.21608/ejchem.2017.1932.1159
  » https://doi.org/10.21608/ejchem.2017.1932.1159
• ¹⁰ Suhailath K, Ramesan MT. Investigations on the structural, mechanical, thermal, and electrical properties of Ce-doped TiO₂/poly(n-butyl methacrylate) nanocomposites. J Therm Anal Calorim. 2019;135(4):2159-69. https://doi.org/10.1007/s10973-018-7285-9
  » https://doi.org/10.1007/s10973-018-7285-9
• ¹¹ Harb SV, Trentin A, de Souza TAC, Magnani M, Pulcinelli SH, Santilli CV, et al. Effective corrosion protection by eco-friendly self-healing PMMA-cerium oxide coatings. Chem Eng J. 2020;383:123219. https://doi.org/10.1016/j.cej.2019.123219
  » https://doi.org/10.1016/j.cej.2019.123219
• ¹² Tunusoğlu Ö, Demir MM. Tailored CeO₂ nanoparticles surface in free radical bulk polymerization of methyl methacrylate. Ind Eng Chem Res. 2013;52(37):13401-10. https://doi.org/10.1021/ie401872y
  » https://doi.org/10.1021/ie401872y
• ¹³ Othman NH, Che Ismail M, Mustapha M, Sallih N, Kee KE, Ahmad Jaal R. Graphene-based polymer nanocomposites as barrier coatings for corrosion protection. Prog Org Coat. 2019;135:82-99. https://doi.org/10.1016/j.porgcoat.2019.05.030
  » https://doi.org/10.1016/j.porgcoat.2019.05.030
• ¹⁴ Liu K, Zhong M. Synthesis of monodispersed nanosized CeO₂ by hydrolysis of the cerium complex precursor. J Rare Earths. 2010;28(5):680-3. https://doi.org/10.1016/S1002-0721(09)60178-2
  » https://doi.org/10.1016/S1002-0721(09)60178-2
• ¹⁵ Lim WF, Zabidi ARM. Effects of oxidation time on the formation of nanosized cerium oxide film from direct current sputtered cerium. Emergent Mater. 2022;5(1):41-9. https://doi.org/10.1007/s42247-022-00370-2
  » https://doi.org/10.1007/s42247-022-00370-2
• ¹⁶ Wang ZL, Feng X. Polyhedral shapes of CeO₂ nanoparticles. J Phys Chem B. 2003;107(49):13563-6. https://doi.org/10.1021/jp036815m
  » https://doi.org/10.1021/jp036815m
• ¹⁷ Liu B, Liu B, Li Q, Li Z, Liu R, Zou X, et al. Solvothermal synthesis of monodisperse self-assembly CeO₂ nanospheres and their enhanced blueshifting in ultraviolet absorption. J Alloys Compd. 2010;503(2):519-24. https://doi.org/10.1016/j.jallcom.2010.05.047
  » https://doi.org/10.1016/j.jallcom.2010.05.047
• ¹⁸ Sun Y, Yuan X, Wang Y, Zhang W, Li Y, Zhang Z, et al. CeO₂ quantum dots anchored g-C₃N₄: synthesis, characterization and photocatalytic performance. Appl Surf Sci. 2022;576:151901.
• ¹⁹ Ali N, Bilal M, Khan A, Nguyen TA, Gupta RK, editors. Polymer nanocomposites: an overview. Amsterdam: Elsevier; 2023
• ²⁰ Muradov M, Addayeva Z, Niftiyev N, Mammadov F, Eyvazova G, Baghirov MB. Dielectric properties of PVA/FeGaInS₄ composites: effects of temperature and concentration of fillers. J Mater Sci. 2025;60(5):2314-27. https://doi.org/10.1007/s10853-024-10591-x
  » https://doi.org/10.1007/s10853-024-10591-x
• ²¹ Baghirov MB, Mammadyarova S, Muradov M, Eyvazova G, Azizian-Kalandaragh Y, Musayeva N, et al. Preparation of anisotropic AgNWs/PVA/Ag₂S nanocomposites via a vapor-phase sulfidation process. RSC Adv. 2024;14(24):16696-705. https://doi.org/10.1039/D4RA01585A
  » https://doi.org/10.1039/D4RA01585A
• ²² Huang J, Zhou J, Liu M. Interphase in polymer nanocomposites. JACS Au. 2022;2(2):280-91. https://doi.org/10.1021/jacsau.1c00430
  » https://doi.org/10.1021/jacsau.1c00430
• ²³ Muradov M, Huseynov E, Conradi M, Malok M, Sever T, Baghirov MB. Effects of gamma radiation on the properties of GO/PVA/AgNW nanocomposites. RSC Adv. 2025;17(17):13574-82. https://doi.org/10.1039/D5RA01344E
  » https://doi.org/10.1039/D5RA01344E
• ²⁴ Pansambal S, Oza R, Borgave S, Chauhan A, Bardapurkar P, Vyas S, et al. Bioengineered cerium oxide (CeO₂) nanoparticles and their diverse applications: a review. Appl Nanosci. 2023;13(9):6067-92. https://doi.org/10.1007/s13204-022-02574-8
  » https://doi.org/10.1007/s13204-022-02574-8
• ²⁵ Bani-Salameh AA, Ahmad AA, Alsaad AM, Qattan IA, Aljarrah IA. Synthesis, optical, chemical and thermal characterizations of PMMA PS/CeO₂ nanoparticles thin film. Polymers (Basel). 2021;13(7):1158. https://doi.org/10.3390/polym13071158
  » https://doi.org/10.3390/polym13071158
• ²⁶ Bakr AM, Darwish A, Azab AA, El Awady ME, Hamed AA, Elzwaey A. Structural, dielectric, and antimicrobial evaluation of PMMA/CeO₂ for optoelectronic devices. Sci Rep. 2024;14(1):2548. https://doi.org/10.1038/s41598-024-52840-8
  » https://doi.org/10.1038/s41598-024-52840-8
• ²⁷ Chau JLH, Hsieh CC, Lin YM, Li AK. Preparation of transparent silica-PMMA nanocomposite hard coatings. Prog Org Coat. 2008;62(4):436-9. https://doi.org/10.1016/j.porgcoat.2008.02.005
  » https://doi.org/10.1016/j.porgcoat.2008.02.005
• ²⁸ Harb SV, Trentin A, Uvida MC, Hammer P. Advanced organic nanocomposite coatings for effective corrosion protection. In: Rajendran S, Kakooei S, Yeganeh M, Li Y, Nguyen T, editors. Corrosion protection at the nanoscale. Amsterdam: Elsevier; 2020. p. 315-343. https://doi.org/10.1016/B978-0-12-819359-4.00017-9
  » https://doi.org/10.1016/B978-0-12-819359-4.00017-9
• ²⁹ Poddar MK, Sharma S, Moholkar VS. Investigations in two-step ultrasonic synthesis of PMMA/ZnO nanocomposites by in–situ emulsion polymerization. Polymer (Guildf). 2016;99:453-69. https://doi.org/10.1016/j.polymer.2016.07.052
  » https://doi.org/10.1016/j.polymer.2016.07.052
• ³⁰ Lu Z, Karakoti A, Velarde L, Wang W, Yang P, Thevuthasan S, et al. Dissociative binding of carboxylic acid ligand on nanoceria surface in aqueous solution: A joint in situ spectroscopic characterization and first-principles study. J Phys Chem C Nanomater Interfaces. 2013;117(46):24329-38. https://doi.org/10.1021/jp4068747
  » https://doi.org/10.1021/jp4068747
• ³¹ Zgheib N, Putaux JL, Thill A, Bourgeat-Lami E, D’Agosto F, Lansalot M. Cerium oxide encapsulation by emulsion polymerization using hydrophilic macroRAFT agents. Polym Chem. 2013;4(3):607-14. https://doi.org/10.1039/C2PY20548C
  » https://doi.org/10.1039/C2PY20548C
• ³² Borah R, Ninakanti R, Nuyts G, Peeters H, Pedrazo-Tardajos A, Nuti S, et al. Selectivity in the ligand functionalization of photocatalytic metal oxide nanoparticles for phase transfer and self-assembly applications. Chemistry. 2021;27(35):9011-21. https://doi.org/10.1002/chem.202100029
  » https://doi.org/10.1002/chem.202100029
• ³³ Huang X, Li L, Li G. Synthesis of CeO₂ assemblies through interaction with short-chain dicarboxylic acids under facile hydrothermal conditions. RSC Adv. 2019;9(49):28581-7. https://doi.org/10.1039/C9RA04245H
  » https://doi.org/10.1039/C9RA04245H
• ³⁴ Jayakumar G, Albert Irudayaraj A, Dhayal Raj A. A comprehensive investigation on the properties of nanostructured cerium oxide. Opt Quantum Electron. 2019;51(9):1-15. https://doi.org/10.1007/s11082-019-2029-z
  » https://doi.org/10.1007/s11082-019-2029-z
• ³⁵ Farahmandjou M, Zarinkamar M, Firoozabadi TP. Synthesis of cerium oxide (CeO₂) nanoparticles using simple CO-precipitation method. Rev Mex Fis [Internet]. 2016 [cited 2025 Nov 17];62:496-9. Available from: http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2016000500496&lng=es&nrm=iso
  » http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2016000500496&lng=es&nrm=iso
• ³⁶ Ramachandran M, Subadevi R, Sivakumar M. Role of pH on synthesis and characterization of cerium oxide (CeO₂) nano particles by modified coprecipitation method. Vacuum. 2019;161:220-4. https://doi.org/10.1016/j.vacuum.2018.12.002
  » https://doi.org/10.1016/j.vacuum.2018.12.002
• ³⁷ Godinho MJ, Gonçalves RFS, Santos LP, Varela JA, Longo E, Leite ER. Room temperature coprecipitation of nanocrystalline CeO₂ and Ce_0.8Gd_0.2O_1.9-δ powder. Mater Lett. 2007;61(8-9):1904-7. https://doi.org/10.1016/j.matlet.2006.07.152
  » https://doi.org/10.1016/j.matlet.2006.07.152
• ³⁸ Hassanzadeh-Tabrizi SA. Precise calculation of crystallite size of nanomaterials: a review. J Alloys Compd. 2023;968:171914. https://doi.org/10.1016/j.jallcom.2023.171914
  » https://doi.org/10.1016/j.jallcom.2023.171914
• ³⁹ Zheng X, Li Y, Zhang L, Shen L, Xiao Y, Zhang Y, et al. Insight into the effect of morphology on catalytic performance of porous CeO₂ nanocrystals for H₂S selective oxidation. Appl Catal B. 2019;252:98-110. https://doi.org/10.1016/j.apcatb.2019.04.014
  » https://doi.org/10.1016/j.apcatb.2019.04.014
• ⁴⁰ Wang G, Mu Q, Chen T, Wang Y. Synthesis, characterization and photoluminescence of CeO₂ nanoparticles by a facile method at room temperature. J Alloys Compd. 2010;493(1-2):202-7. https://doi.org/10.1016/j.jallcom.2009.12.053
  » https://doi.org/10.1016/j.jallcom.2009.12.053
• ⁴¹ Parlak O, Demir MM. Toward transparent nanocomposites based on polystyrene matrix and PMMA-grafted CeO₂ nanoparticles. ACS Appl Mater Interfaces. 2011;3(11):4306-14. https://doi.org/10.1021/am200983h
  » https://doi.org/10.1021/am200983h
• ⁴² Paschalidou P, Theocharis CR. Surface properties of ceria synthesized using Triton-X based reverse microemulsions. RSC Adv. 2019;9(12):7025-31. https://doi.org/10.1039/C8RA08947G
  » https://doi.org/10.1039/C8RA08947G
• ⁴³ Duan G, Zhang C, Li A, Yang X, Lu L, Wang X. Preparation and characterization of mesoporous zirconia made by using a poly (methyl methacrylate) template. Nanoscale Res Lett. 2008;3(3):118-22. https://doi.org/10.1007/s11671-008-9123-7
  » https://doi.org/10.1007/s11671-008-9123-7
• ⁴⁴ Amrouni N, Meziane A, Boussaid A. Preparation and characterization of potato starch/bentonite organophylized by SDS. Rev Mex Fis. 2025;71(2):1-8. https://doi.org/10.31349/RevMexFis.71.021001
  » https://doi.org/10.31349/RevMexFis.71.021001
• ⁴⁵ Hafizah MAE, Riyadi AF, Manaf A. Particle size reduction of polyaniline assisted by anionic emulsifier of sodium dodecyl sulphate (SDS) through emulsion polymerization. I Mater Sci Eng. 2019;515:012080. https://doi.org/10.1088/1757-899X/515/1/012080
  » https://doi.org/10.1088/1757-899X/515/1/012080
• ⁴⁶ Viana RB, Da Silva ABF, Pimentel AS. Infrared spectroscopy of anionic, cationic, and zwitterionic surfactants. Adv Phys Chem. 2012;2012:1-14. https://doi.org/10.1155/2012/903272
  » https://doi.org/10.1155/2012/903272
• ⁴⁷ Antony N, Benita Sherine H, Rajendran S. Inhibition and biocide actions of sodium dodecyl sulfate-Zn²⁺ system for the corrosion of carbon steel in chloride solution. Port Electrochem Acta. 2010;28(1):1-14. https://doi.org/10.4152/pea.201001001
  » https://doi.org/10.4152/pea.201001001
• ⁴⁸ Eriksson M, Goossens H, Peijs T. Influence of drying procedure on glass transition temperature of PMMA based nanocomposites. Nanocomposite. 2015;1(1):36-45. https://doi.org/10.1179/2055033214Y.0000000005
  » https://doi.org/10.1179/2055033214Y.0000000005
• ⁴⁹ Serenko OA, Roldughin VI, Askadskii AA, Serkova ES, Strashnov PV, Shifrina ZB. The effect of size and concentration of nanoparticles on the glass transition temperature of polymer nanocomposites. RSC Adv. 2017;7(79):50113-20. https://doi.org/10.1039/C7RA08152A
  » https://doi.org/10.1039/C7RA08152A
• ⁵⁰ Hirata T, Kashiwagi T, Brown JE. Thermal and oxidative degradation of poly(methyl methacrylate): weight loss. Macromolecules. 1985;18(7):1410-8. https://doi.org/10.1021/ma00149a010
  » https://doi.org/10.1021/ma00149a010
• ⁵¹ Leão AD, Silva LA, Ribeiro FOS, Silva DA, França EJ, Aquino KAS, et al. Influence of nonmodified layered double hydroxide (LDH) metal constituents in PMMA/LDH nanocomposites. J Inorg Organomet Polym Mater. 2021;31(2):836-50. https://doi.org/10.1007/s10904-020-01742-z
  » https://doi.org/10.1007/s10904-020-01742-z
• ⁵² Kashiwagi T, Brown JE, Inaba A, Hatada K, Kitayama T, Masuda E. Effects of Weak Linkages on the thermal and oxidative degradation of poly(methyl methacrylates). Macromolecules. 1986;19(8):2160-8. https://doi.org/10.1021/ma00162a010
  » https://doi.org/10.1021/ma00162a010
• ⁵³ Zeng WR, Li SF, Chow WK. Review on chemical reactions of burning poly(methyl methacrylate) PMMA. J Fire Sci. 2002;20(5):401-33. https://doi.org/10.1177/0734904102020005482
  » https://doi.org/10.1177/0734904102020005482
• ⁵⁴ Reyes-Acosta MA, Torres-Huerta AM, Domínguez-Crespo MA, Flores-Vela AI, Dorantes-Rosales HJ, Andraca-Adame JA. Thermal, mechanical and UV-shielding properties of poly(methyl methacrylate)/cerium dioxide hybrid systems obtained by melt compounding. Polymers (Basel). 2015;7(9):1638-59. https://doi.org/10.3390/polym7091474
  » https://doi.org/10.3390/polym7091474
• ⁵⁵ Latha P, Prakash K, Karuthapandian S. Facile fabrication of visible light-driven CeO₂/PMMA thin film photocatalyst for degradation of CR and MO dyes. Res Chem Intermed. 2018;44(9):5223-40. https://doi.org/10.1007/s11164-018-3419-8
  » https://doi.org/10.1007/s11164-018-3419-8
• ⁵⁶ Park SM, Kim DA, Jo JK, Jun SK, Jang TS, Kim HW, et al. Ceria-incorporated biopolymer for preventing fungal adhesion. ACS Biomater Sci Eng. 2021;7(5):1808-16. https://doi.org/10.1021/acsbiomaterials.0c01039
  » https://doi.org/10.1021/acsbiomaterials.0c01039

Edited by

• Associate Editor:
  Rodrigo Orefice.

• Editor-in-Chief:
  Luiz Antonio Pessan.

Publication Dates

• Publication in this collection
  10 July 2026
• Date of issue
  2026

History

• Received
  17 Nov 2025
• Reviewed
  16 May 2026
• Accepted
  04 June 2026