Stabilization of gels and emulsions in the ternary water/eugenol/ poloxamer 407-system: Physicochemical characterization and potential application as encapsulation platforms Agustina Fañani a,b,*, Belén Arcos-Álvarez c, Pamela Banegas a,b, Luciana Rocha a,b, Julia Monge-Corredor c, Ramón G. Rubio c,d, Eduardo Guzmán c,d,**, Alejandro Lucia a,*** a Grupo de Manejo Integrado y Bioecología de Artrópodos Dulceacuícolas (MIyBAD) - Instituto de Ecología y Desarrollo Sustentable (INEDES, CONICET-UNLu), Ruta 5 y Avenida Constitución, Luján, Buenos Aires 6700, Argentina b Departamento de Ciencias Básicas, Universidad Nacional de Luján, Ruta 5 y Avenida Constitución, Luján, Buenos Aires 6700, Argentina c Departamento de Química Física-Facultad de Ciencias Químicas-Universidad Complutense de Madrid Ciudad Universitaria s/n, Madrid 28040, Spain d Unidad de Materia Condensada, Instituto Pluridisciplinar-Universidad Complutense de Madrid, Paseo de Juan XXIII, 1, Madrid 28040, Spain G R A P H I C A L A B S T R A C T A R T I C L E I N F O Keywords: Dispersions Insecticides Nanocarriers Pest control A B S T R A C T The ternary system water/eugenol/poloxamer 407 can form a variety of phases that are strongly influenced by the mixture composition and the thermal history of the system. In this study, we investigated the stabilization of emulsion and gel-like systems in which eugenol is encapsulated in a poloxamer 407 matrix. Our results reveal the complex interplay between poloxamer 407 and eugenol compositions in the stabilization single-phase systems at 25ºC. Increasing concentrations of poloxamer were found to incorporate higher amounts of eugenol into * Corresponding author at: Grupo de Manejo Integrado y Bioecología de Artrópodos Dulceacuícolas (MIyBAD) - Instituto de Ecología y Desarrollo Sustentable (INEDES, CONICET-UNLu), Ruta 5 y Avenida Constitución, Luján, Buenos Aires 6700, Argentina. ** Corresponding author at: Departamento de Química Física-Facultad de Ciencias Químicas-Universidad Complutense de Madrid Ciudad Universitaria s/n, Madrid 28040, Spain. *** Corresponding author. E-mail addresses: agusfa@outlook.com (A. Fañani), eguzmans@ucm.es (E. Guzmán), luciaalejandro@yahoo.com.ar (A. Lucia). Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects journal homepage: www.elsevier.com/locate/colsurfa https://doi.org/10.1016/j.colsurfa.2024.135474 Received 12 August 2024; Received in revised form 13 September 2024; Accepted 30 September 2024 Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 Available online 1 October 2024 0927-7757/© 2024 Published by Elsevier B.V. mailto:agusfa@outlook.com mailto:eguzmans@ucm.es mailto:luciaalejandro@yahoo.com.ar www.sciencedirect.com/science/journal/09277757 https://www.elsevier.com/locate/colsurfa https://doi.org/10.1016/j.colsurfa.2024.135474 https://doi.org/10.1016/j.colsurfa.2024.135474 Phase behavior Thermal annealing emulsion-like dispersions, effectively preventing coalescence and Ostwald ripening. However, high concentra tions of poloxamer 407 induced gelation of these dispersions, resulting in eugenol-loaded poloxamer 407 gels. The thermal annealing of the emulsions at 65◦C for 1 h followed by equilibration at room temperature allows the extension of the compositional range for the formation of homogeneous single-phase systems providing a strategy to modulate the phase diagram of the ternary system. Additionally, the encapsulation of hydrophobic pesticides in gel-like matrices was investigated, showing uniform distribution and consistent loading capacity (approximately 0.70 % w/w) across different pesticides which may contribute to facilitate the environmental distribution and efficacy of the encapsulated molecules. This research highlights the potential of eugenol/ poloxamer 407-based systems as an environmentally friendly platform for the encapsulation and delivery of hydrophobic active molecules, offering a versatile solution for various applications. 1. Introduction Seeking platforms to solubilize and/or encapsulate poorly water- soluble active compounds is a challenge for science and technology. However, there are important limitations for the design and fabrication of efficient platforms. Among these limitations are included the neces sity of specific machinery for their preparation, high costs of pro ductions, limited scalability, and limited physico-chemical stability. These need to be overcome to guarantee the production of formulations with high effectiveness [1,2]. Colloidal carriers offer promising properties to be used for the encapsulation of poorly water-soluble active compounds, and can contribute to enhance their availability, dissolution rate, dispersion and distribution in an aqueous environment [3–6]. For instance, the simplicity of the physical incorporation of drugs within micelles of block copolymer containing hydrophobic core has stimulated a vast piece of research focused on its application to enhance the solubility of poorly active ingredients [7–10]. Oil-in-water nanoemulsions can encapsulate, protect, and promote controlled release of lipophilic bioactive molecules [11–14]. In fact, they provide good protection to the entrapped bioactive molecules against the effects of external conditions, as they encapsulate bioactive molecules in a confined environment separated with the external me dium through a emulsifier shield that can allow a partial exchange of molecules between the inner core and the external medium. Nano emulsions can be prepared simply by blending oil, water, and emulsi fiers, in the right proportion, with mild agitation [15]. In particular, nanoemulsions stabilized by amphiphilic block copolymers with surface activity are a very promising alternative for the encapsulation of different families of bioactive compounds, ranging from biomedical actives to different types of molecules with insecticidal and fungicidal activity and from food ingredients to cosmetic actives. The interest in the use of amphiphilic block copolymers with surface activity, especially those belonging to the family of the poloxamer or Pluronic, relies on their possible use as antifoaming and wetting agents, dispersants, thickeners, and emulsifiers. The poloxamers are an amphiphilic molecule, that above a critical temperature and concen tration; self-aggregate in aqueous solutions to form supramolecular nanostructures with a hydrophobic core of polyoxypropylene (poly (propylene oxide)) surrounded by a hydrophilic corona of polyoxy ethylene (poly (ethylene oxide)) [16,17]. Thus, poloxamers can be exploited to encapsulate hydrophobic substances within the hydropho bic core, enhancing their bioavailability and dispersion. When the encapsulated substances are hydrophobic liquids, the obtained disper sions can be considered emulsion-like systems. On the other, poloxamer copolymers presents a reduced toxicity [18]. Moreover, they exhibit thermoreversible gelation, which has stimulated a considerable interest in their potential use for drug delivery [19,20]. The obtained gel can be cooled down and/or warmed up several times without any significant modification in their properties [18]. The mechanism of gel formation in poloxamers have been discussed by several authors and is still a topic under debate in the literature. In fact, there are several possible expla nations for such gelation process: (i) dehydration of the poly oxypropylene groups in the micelle core [21], (ii) change in the micellar volume [22] or (iii) decrease in the critical micelle concentration and increase in the aggregation number [23]. The adaptability of polox amers is particularly beneficial for applications requiring specific release profiles, contributing to the development of efficient, scalable, and versatile delivery systems. In recent years, poloxamer copolymers have been successfully used for the encapsulation of essential oils [24]. Essential oils are liquid mixtures containing low molecular weight lipophilic compounds, mainly terpenoids and phenylpropanoids, that result from different biogenetic pathways [25]. Their use is particularly welcome since many of them are considered GRAS (Generally Recognized as Safe) by both the US FDA (Food and Drug Administration) and the EPA (Environmental Protection Agency), thus avoiding hazards for public health and envi ronment [26]. However, their poor water solubility and high volatility during processing are major drawbacks for their exploitation in the consumer products and industrial processes [27]. One of the most extensively used essential oil is the clove oils, which is obtained by distillation of the flower, buds, stems, and leaves of the clove tree (Syzygium aromaticum) [28]. Eugenol, 4-allyl-2-methoxyphe nol, is its main component, accounting for more than 80 % in weight of clove bud oil, playing an essential role in the strong antioxidant properties and antibacterial, antifungal, and antiviral activities [27,29, 30]. Essential oils or their individual components can be included in formulations for pest control directly as the active ingredient or as ad juvants with pesticide activity. The latter use is especially relevant because it has been recently reported the existence of synergistic effects against insect pests between essential oils or their compounds, and different synthetic insecticides [31–38]. The use of essential oils not only favors the solubility of the active principle, but also makes the whole formulation more sustainable from an environmental point of view Lucia et al. [37] has evidenced that eugenol in water nanoemulsions stabilized by poloxamer 407 can be used as platforms for the encapsu lation of the poorly water-soluble insecticide pyriproxyfen. These encapsulation platforms present a higher encapsulation efficiency than simple copolymer micelles (15 times higher) and good long-term sta bility (at least 24 months). The simplicity of the methodology used for the encapsulation, in which only mild shaking is needed to obtain stable dispersions, should be considered an important advantage for the development of formulations for real field application, because it is avoided the use of complex machinery, e.g., high pressure homoge nizators, for its preparation. This facilitates the in-situ preparation of the formulations when it is required, reducing the costs associated with their preparation and transport [37], and consequently the ecological foot print. Furthermore, the use of aqueous formulations would contribute to reduce the risk of fire during the handling and transport [39]. In this work, the ternary water-eugenol-poloxamer 407 is studied to determine the different phases that can appear depending on the mixture composition at room temperature (25ºC), and the properties of the obtained aqueous dispersion. Moreover, the effect of the thermal annealing at 65ºC is explored as strategy to modulate the nature of the formulation. Last but not least, the use of gel-like mixtures obtained in water-eugenol-poloxamer 407 system as platform for the encapsulation of molecules with insecticidal activity is investigate. It is important to A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 2 note that in most of the previous research on ternary systems involving water, essential oil compounds and emulsifiers have been focused pri marily on their behavior at room temperature [40–42]. These studies have often overlooked the effect of thermal treatments on the phase behavior of such mixtures [43]. In addition, many of such studies focus only on the study of a limited number of compositions, resulting in an incomplete perspective of the phase behavior of the system [44–46]. In contrast, this study aims to fill this gap by providing a thorough inves tigation of how thermal annealing affects the phase behavior of water/eugenol/emulsifier systems, which may provide a deep under standing of how thermal treatments can be used to modulate the prop erties of these ternary systems. Moreover, in this work, a copolymer belonging to the poloxamer family has been used as emulsifier instead of the most commonly used Tween surfactants [47]. It is hoped that this systematic work can provide important insight on the design of eco-friendly and sustainable carriers for different type of molecules, and how to modulate the properties of the obtained carriers, paving the way for more effective and versatile formulations in various applications. 2. Materials and methods 2.1. Chemicals Eugenol (4-allyl-2-methoxyphenol) with a purity ≥ 99 % and poloxamer 407, also known as Pluronic® F-127, were purchased from Sigma-Aldrich (Saint Luis, MO, USA). Poloxamer 407 (P407) is a triblock copolymer with an average molecular weight of 12.6 kDa (4.4 kDa for each polyethylene oxide terminal block and 3.8 kDa for the central polypropylene oxide one). The chemicals were used as received without further purification. Fig. 1 displays the chemical structures of eugenol and poloxamer 407. The samples were prepared using ultrapure deionized water (Milli-Q water), with a resistivity greater than 18 MΩ•cm and a total organic content lower than 6 ppm (Milli-Q quality), obtained from a multicartridge purification system AquaMAX-Ultra 370 Series (Young Lin Instrument Co., Ltd., Gyeonggi-do, South Korea). 2.2. Preparation and classification of mixtures containing eugenol and P407 The samples were prepared in glass tubular vials (16 mL) following a procedure adapted from our previous publication [37]. Poloxamer 407 solutions were prepared at concentrations 2.5, 5, 7.5, 10, 12.5 and 15 % w/w. First, eugenol was poured into the tube containing the copolymer solution to a final concentration in the range 1–19 %w/w. The last stage involves in the homogenization of the mixtures by mild shaking in vortex at 2200 rpm for 1 min. The samples were prepared by two methods: (i) spontaneous emulsification method at 25ºC, and (ii) spon taneous emulsification at 25ºC followed by thermal annealing at 65ºC for 1 h in a thermostatic bath. It is worth to mention that three independent replicates were prepared for each of the study ternary mixtures. 2.3. Evaluation of the sample nature The stability and nature of the prepared samples were assessed by visual inspection after 48 h of aging. Thus, it was possible to classify the mixtures in two groups; MS for single-phase dispersions with a pale orange/yellow color formed as a result of the dispersion of eugenol nanodroplets in water (note that bare eugenol is an oily liquid with a pale-yellow color) and BS for phase separated systems. Among phase separated systems, mixtures with different characteristics were found: (i) mixtures characterized by the presence of sedimented eugenol droplets at the bottom of the vial (BS+, BS++, BS+++, note that the number of + sign is a qualitative indicator of the degree of phase sep aration in the mixtures); (ii) mixtures with two emulsified phases of different composition (BSE), and (iii) mixtures characterized by a poor dispersion of the eugenol in a gelled P407 matrix (BSG). The latter type of mixtures was found only when the spontaneous emulsification method at room temperature was used. Single-phase dispersions (MS) were classified as gels or emulsions by the tube inversion method [20,48–50] the samples were tested by quick inversion of the sample tubes and visual observation for changes in flow behavior. Considering the visual observation of MS samples emulsions and gels were classified according to their turbidity as follows: Emul sions: E: Emulsion without turbidity, E+: slightly cloudy emulsion, E++: cloudy emulsion, E+++: Milky Emulsion and E++++: Gel-like emul sion. Gels: GEL: Gel without turbidity, GEL+: slightly cloudy gel, GEL++: cloudy gel. 2.4. Characterization techniques The obtained systems were characterized by a pool of techniques offering different information about their physico-chemical properties. Dynamic Light Scattering (DLS) measurements were used to evaluate the droplet size distribution of the obtained eugenol droplet in the aqueous medium for non-turbid liquid dispersions in terms of the apparent hydrodynamic diameter (dapp h ). DLS experiments were carried out using a Zetasizer Nano ZS (Malvern Instruments Ltd., United Kingdom) at 25ºC in quasi-backscattering configuration (scattering angle, θ = 173º) using radiation from the red line of a He-Ne laser (wavelength, λ = 632 nm). Prior to measurements, the samples were passed through an inert filter with a pore size of 0.45 μm (Fisher Sci entific, Hampton, NH, USA) and placed in an optical glass cell (model Hellma® 6030-OG, Germany). Additional information on DLS experi ments can be found in previous publications [24,51,52]. The DLS results reported in this work are the average of five independent measurements, which present in all the cases, a deviation lower than 5 %). Conductivity measurements of the aqueous dispersions were per formed using a Methrom 856 Conductimeter (Methrom AG, Herisau, Switzerland) equipped with a 5-ring platinum conductivity cell (Meth rom AG, Herisau, Switzerland). The reported measurements, which correspond to the average of 10 independent measurement, consistently showed an accuracy and reproducibility of more than 95 %. Fluorescence spectroscopy was used to study the incorporation of eugenol into the hydrophobic core provided by P407 using an FP-6500 fluorescence spectrophotometer (Jasco Inc., Easton, USA). An excita tion wavelength of 280 nm was chosen based on the data reported in the literature [53]. This wavelength would provide optimal excitation effi ciency for eugenol due to its optical properties. The spectra reported in this work are the average of three independent spectrum for each studied sample, which present in all the cases, a deviation lower than 10 %. Fig. 1. Molecular structures for eugenol (a) and P407 (b). Notice that in panel (b) corresponding to the molecular formula of P407 x, y and z indicate the number of monomers for each block, in the considered case x=z=100 and y=65. A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 3 2.5. Encapsulation of pesticides in gel-like mixtures Four active molecules were used as models to evaluate the encap sulation capacity of the eugenol-poloxamer 407 gel-like mixtures. The insecticides Permethrin (purity 98 %), Lufenuron (purity 98.5 %); and Pyriproxyfen (purity 97 %) were provided by Chemotecnica S.A (C. Spegazzini, Buenos Aires, Argentina), and the fungicide tebuconazole (purity 98.5 %) was supplied by Química Bosques S.A. (Buenos Aires, Argentina). The gels (three replicates for each composition) used for solubilization, and encapsulation of these active molecules (at concen tration 0.7 %w/w) contain poloxamer 407 and eugenol in concentra tions of 15 %w/w and 4 %w/w, respectively. The gels were prepared in 5 mL syringes. After 6 months of storage at 25 ◦C, the syringe was divided into 4 zones, the lower, the upper, and the two central zones. From each zone 2 samples were taken and the amount of active principle in that zone was determined by gas chromatography coupled to a mass spectrometric detection (GC-MS). The preparation of samples for GC-MS determination of the concentration of each active molecule was done by the dilution of an aliquot in 5 mL of dichloromethane and 1 mL of water. The obtained samples were shaken (5 min), and then kept at room temperature for 24 h before their analysis by GC-MS. The analysis of each sample was performed in duplicate using a GC-2010 instrument coupled with a QP2010 mass spectrometer detector (Shimadzu, Kyoto, Japan) in the electron impact mode (70 eV). Samples were analyzed using an apolar GC capillary column DB-5MS (30 m x 0.25 mm i.d. and 0.25 µm coating thickness) (Agilent J&W Scientific, Santa Clara, CA, USA). The GC column temperature was maintained at 100 ºC for 5 min, then programmed from 100 to 280 ◦C at a rate of 10 ◦C/min, this final temperature was held for 25 min. Helium (99.99 %) was used as the carrier gas at a 28.5 mL/min caudal (total flow), the column flow was 0.5 mL/min. The detector temperature was 300 ºC and all samples were made in the split mode (split ratio:50). The injector port was maintained at 260◦C. The mass spectrometer scanned in the m/z range 30 and 500, allowing a qualitative determination of compounds. The determination of the concentration of each compound requires of a calibration curve. This was carried out using solutions in dichloromethane of each com pound. Two replicates of each concentration were analyzed, and the concentration for each compound in the different zones was determined as the average value. 3. Results and discussion 3.1. Phase diagram of water/Eugenol/poloxamer 407 system obtained using spontaneous emulsification at 25ºC A preliminary step towards the use of water/eugenol/poloxamer 407 systems as potential platforms to encapsulate poorly water-soluble molecules is the determination of the composition range in which single-phase and two-phase systems appears, i.e., phase-separated mixtures, appear in the phase diagram of the ternary mixture. The analysis of the different samples studied has allowed us to identify in the phase diagram three different type of single-phase systems (oil in water emulsions, gels, and gel-like emulsion) together with phase-separated mixtures. For ternary mixtures prepared by the spontaneous emulsifi cation method at 25ºC, i.e., by simply homogenization under mild stir ring (<1000 rpm) of the components, two different types of homogeneous systems, emulsions (○) and gels (□), were obtained, depending on the concentration of eugenol, poloxamer 407 and water. Fig. 2 reports the phase diagram for the studied ternary mixtures within the considered composition range. The analysis of the phase diagram evidences that it is only possible to obtain emulsion-like dispersions, i.e., liquid homogeneous dispersions, for poloxamer 407 and eugenol concentrations in the ranges 2.5–12.5 % w/w and 1–4 %w/w, respectively. The increase of the concentration of eugenol leads to the phase separation, whereas the increase in the poloxamer 407 results in the gelation of the mixtures. This occurs for the highest concentrations of copolymer studied, and eugenol concentra tions in the range 1–8 %w/w. It should be noted that the gelation pro cess has also been reported for poloxamer 407 solution in water without eugenol. However, the amount of copolymer needed for obtaining these gels is slightly higher than that reported here for the ternary systems containing eugenol [54]. It is worth mentioning that poloxamer gels containing oils (oleogels) have also been reported using olive oil as oil phase. [55] Fig. 3 shows a series of water/eugenol/mixtures with different compositions that confirm the above discussion in relation to the phase diagram. In Fig. 3a, it can be observed that as the percentage of eugenol in creases, i.e., as the weight fraction of the oily phase increases, there is a change in the color of the dispersions from a pale yellow to a strong orange/brown color and simultaneously the turbidity of the samples increases, which is reasonable considering the increase in content of the dispersed phase. In addition, as can be seen with increasing oil content in the mixtures, there is a transition to phase separation (samples more to the right in the figure). This separation may occur because as the percentage of eugenol increases at a constant concentration of polox amer, the availability of the latter to accommodate the oil by forming stable droplets decreases. The phase separation phenomenon is more evident in the samples shown in Fig. 3b, where it is clearly observed that as the oil phase content increases in the range 1–6 % w/w, a clear eugenol sediment, whose density is higher than that of water (1.06 g/cm [3] at 25◦C), appears at the bottom of the vial. As mentioned above, increasing the concentration of poloxamer 407 at a fixed concentration of the eugenol can cause a significant increase in viscosity. This transition can be interpreted by considering that as the concentration of copolymer increases, the number of aggregates that can contain the eugenol increases sharply, reaching a point where the in dividual droplets begin to percolate without coalescing. This signifi cantly increases the viscosity of the mixtures due to the formation of a system where the droplets are densely packed, resulting in a gel-like state, and the eugenol remains encapsulated in a highly viscous matrix formed by the copolymer. Figs. 3c and 3d shows an example of the formation of such gels by varying the composition. Fig. 2. Phase diagram for the ternary water/eugenol/Poloxamer 407 systems for mixtures prepared by the spontaneous emulsification method at 25ºC. The compositions of the different components are in weight percentage (%w/w). The symbols indicate the different compositions studied: Phase separated sys tems (BS); Emulsions (E: Emulsion without turbidity, E+: slightly cloudy emulsion, E++: cloudy emulsion) and Gels (G: Gel without turbidity, G+: slightly cloudy gel, G++: cloudy gel). A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 4 3.2. Compositional control of the phase formation The previous section has highlighted the wide variety of phases that can emerge within the ternary water/eugenol/Poloxamer 407 system, depending on the specific compositional range under consideration. This phase diversity arises from a complex and dynamic interplay between the concentrations of the copolymer and eugenol, which may influence the structural and thermodynamic behavior of the system. In agreement with the previous work by Lucia et al. [37], the detailed analysis of the phase diagram, and the different regions of stability and instability appearing as function of their compositions, evidence the existence of a threshold value for the ratio between the weight contents of eugenol and poloxamer 407 in the mixture (R ratio: eugenol concen tration/poloxamer concentration) above which the emergence of the phase separation should occur (BS). This suggests that a minimum concentration of copolymer is required to create a hydrophobic envi ronment capable of ensuring the effective dispersion of eugenol within the aqueous phase. This agrees with the finding by Sugumar et al. [56] for orange oil-in-water nanoemulsions stabilized by a surfactant belonging to the Tween family. They found that the stabilization of the oil droplets at a fixed concentration was only possible when the sur factant concentration overcome a certain threshold value. Moreover, they reported that an excess of surfactant may be deleterious for the stability of the dispersions. However, the compositional range evaluated by Sugumar et al. [56] was very limited to extract conclusions. The findings from the present study indicate that determining this threshold value is not always straightforward, as it appears to be highly dependent on the specific composition of the mixture. In fact, for both liquid and gel samples, the threshold value of R for undergoing in the phase separation decreases as the concentration of the copolymer increases. However, there is an increase in the threshold value of R for guaranteeing the homogeneity of the sample, i.e., formation of emulsion-like or gel-like mixtures, when the composition pass from the region corresponding to emulsion-like dispersion to that corresponding to the formation of gel systems. This is clearer from the representation in Fig. 4 where the type of mixtures as a function of the value of the R ratio and the concentration of copolymer (cP407) is reported. In detail, the results show that for liquid mixtures, the threshold value of R for avoiding the phase separation oscillates between values close to 0.70 for mixtures with the lowest copolymer concentration to values about 0.3 for the highest concentrations of poloxamer allowing the preparation of emulsion-like dispersions. Above, the threshold value the samples undergo phase separation. It should be noted that the turbidity (E to E+++) of emulsions increases as the R ratio approaches to the threshold value (see Fig. 3a). It is important to note that the "+" symbols used to describe certain samples provide a qualitative measure of their turbidity. As the number of "+" symbols increases, so does the turbidity of the sample. In the case of emulsions, "E" denotes transparent emulsions with no signs of turbidity, while "E+++" refers to milky emulsions with high turbidity. For more detailed information, please refer to the subsection Evaluation of the Sample Nature. The above discussion shows that there is no linear correlation be tween the maximum amount of eugenol incorporated per copolymer molecule, which is highly dependent on the specific composition of the mixture. The results for the gel-like mixtures are similar to those ob tained for homogeneous liquid dispersions, decreasing the threshold value of R for phase separation with the increase in the poloxamer concentration. 3.3. Size characterization of the dispersed droplets It has been possible to estimate the size of the droplets constituting the dispersions in terms of their apparent hydrodynamic diameter (dapp h ) by means of DLS measurements. This procedure requires an analysis of the autocorrelation functions of the intensities (g(2)(t)-1) obtained experimentally from each of the dispersions studied, except for turbid, phase-separated or gel samples. In brief, the autocorrelation function of intensities describes how the intensity of a fluctuating signal, such as light in DLS, correlates with itself over time. Thus, measuring the degree of similarity between the intensity values at two different time points as a function of the time delay between them. For a system in motion, such as droplets in an aqueous environment, the autocorrelation function decays over time, with the rate of decay providing information about the dynamics of the system, which helps to obtain information related to the particle size or diffusion speed. [57] Fig. 5a shows the autocorrelation functions of intensities obtained by DLS for homogeneous liquid dispersions characterized by a fixed amount of eugenol (1 % w/w) and increasing concentrations of polox amer 407 (cP407). In addition, Fig. 5b shows the apparent hydrodynamic Fig. 3. Set of images corresponding to water/eugenol/poloxamer 407 ternary mixtures with different compositions. (a) Mixtures with a fixed poloxamer 407 concentration of 7.5 %w/w and increasing eugenol concentrations (numbers indicated in the figure). (b) Mixtures with a fixed poloxamer 407 concentration of 2.5 %w/w and increasing eugenol concentrations (numbers indicated in the figure). (c) Mixtures with a fixed poloxamer 407 concentration of 15 %w/w and increasing eugenol concentrations (numbers indicated in the figure). (d) Details of the inverted test tube for one of the gelling samples in panel c (poloxamer 407 concentration of 15 %w/w and eugenol concentration 5). A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 5 diameter distributions obtained by analyzing the intensity autocorrela tion functions of Fig. 5a. The results obtained for other compositions follow a similar trend, where increasing concentrations of Poloxamer 407 improve the distribution of eugenol within the aqueous medium. However, the series presented here was selected because it spans a broader range of compositions, allowing for the analysis of a larger and more representative set of samples. This provides a more comprehensive understanding of how varying the composition influences the behavior of the system. The dependence of the size of the droplets on the con centration of emulsifiers agree with the results reported for other emulsions of essential oils and essential oil components, independently of the used emulsifier. [46,56] The analysis of the autocorrelation functions of the intensities ob tained for samples with increasing concentrations of Poloxamer 407, where the percentage of eugenol is kept constant (1 % w/w), shows a great diversity of behavior, which is indicative of the different states of the samples and their proximity to the phase boundaries. Thus, when the copolymer concentration is low, the autocorrelation functions of the intensities obtained show a multimodal character, indicating the pres ence in the medium of scattering centers with dynamics sufficiently separated in time. This can be understood considering that when the copolymer concentration is not very high, the coating density of the eugenol droplets is relatively low, which can promote coalescence and Ostwald ripening phenomena. This results, as reflected the hydrody namic diameter distributions (Fig. 4b), in the appearance of droplet populations with two different average sizes, with the smaller ones having an average diameter around 15–20 nm, while the size of the droplets resulting from coalescence and Ostwald ripening phenomena reaches sizes in the range of 200–300 nm. Increasing the concentration of poloxamer 407 increases the density of material available to coat the interface between the eugenol droplet and the continuous phase, reducing the phenomena that tend to desta bilize the emulsions. This leads to the appearance of autocorrelation functions of intensities of monomodal character, which are translated into apparent hydrodynamic diameter distributions in which only a population of droplets appears with a size similar to that previously observed for the smaller droplet found in the samples prepared with a relatively low concentration of copolymer. A further increase in the concentration of Pluronic F-127 leads to a more complex situation, returning to systems characterized by a multimodal autocorrelation function, giving rise to three populations of scattering centers of different sizes. The first of the scattering centers that can be identified are the eugenol droplets with a mean diameter close to 15 nm, which is similar to what was found previously. But next to them, two other populations of scattering centers appear, one of larger size than the previously mentioned droplets and the other of smaller size. The latter could be identified as individual copolymer micelles that appear due to the existence of an excess in the amount of copolymer needed to coat the eugenol droplets. On the other hand, the larger scattering centers could be justified by an aggregation of droplets due to the high density of objects present in the medium, which favors their percolation as the concentration of poloxamer increases, as discussed in the previous section. The above discussion focused on the effect of Poloxamer 407 on the droplet size and stability of emulsion-like dispersions. However, eugenol also plays a very important role in the stability of the emulsions, as discussed above, and therefore a strong influence of the eugenol content on the droplet size can be expected. This was evaluated by studying the effect of increasing the concentration of eugenol (ceugenol) in dispersions in which the concentration of Pluronic F-127 is maintained using DLS (see Fig. 6). Increasing the concentration of eugenol at a fixed poloxamer 407 concentration causes the autocorrelation functions of intensities shown in Fig. 6a to undergo a transition from a monomodal to a multimodal character. This is also reflected in the apparent hydrodynamic diameter distributions (Fig. 6b). At low eugenol concentrations, a single distri bution appears characterized by an average apparent hydrodynamic diameter in the range of 15–20 nm, and this contribution is accompa nied by a larger one (around 600 nm) as the eugenol concentration increases. 3.4. Conductimetric study of emulsion-like dispersions Fig. 7 shows the dependence of the ionic conductivity of the emul sions on the concentration of Pluronic F-127 for mixtures with fixed concentration of eugenol. The results clearly show that both poloxamer 0 4 8 12 16 0.0 0.5 1.0 R cP407 (% w/w) Fig. 4. R ratio (ratio between eugenol concentration and poloxamer one)-cP407 diagram reporting the specific compositional regions where the different types of samples are formed. ( ) Emulsion-like dispersions, ( ) gel-like systems, and ( ) phase-separated mixtures. A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 6 407 and eugenol concentration cause an increase in ionic conductivity, this a priori is an unexpected result, given that neither of the two has an ionic character. The increase in ionic conductivity with Pluronic F-127 concentration is the result of the increase in the concentration of droplets stabilized by the copolymer and free micelles (at the highest concentrations) diffusing into the solution, which leads to an increase in the number of ionic charge carriers according to the work of Barreiro-Iglesias et al. [58] On the other hand, the effect of the increase in conductivity with eugenol concentration could be the result of an increase in the instability of the emulsions as a result of the coalescence of the dispersed phase discussed above [59]. 3.5. Spectroscopy evidence of the confinement of eugenol within poloxamer 407 stabilized nanodroplets The use of fluorescence spectroscopy provides information at the molecular level about the distribution of eugenol within the hydro phobic environment created by poloxamer 407. For this purpose, the emission spectrum is evaluated after excitation at a fixed wavelength; in the case studied in this work, the wavelength chosen for excitation was 280 nm. Fig. 8 shows the fluorescence emission spectrum, as the dependence of the Fluorescence intensity (IF) on the emission 100 101 102 103 104 105 106 0.0 0.2 0.4 0.6 0.8 1.0 cP407 (% w/w) 2.5 5.0 7.5 10.0 12.5 g(2 ) (t) -1 t (µs) 100 101 102 103 0 5 10 15 0.0 2.5 5.0 7.5 10.0 12.5 (b) cP407 (% w/w) 2.5 5.0 7.5 10.0 12.5 dapp h (nm) In te ns ity (% ) c P4 07 (% w/ w) (a) Fig. 5. Results obtained by DLS for transparent liquid dispersions with a fixed amount of eugenol (1 % w/w) and different concentrations of Poloxamer 407. (a) Autocorrelation functions of intensities. (b) Apparent hydrodynamic diam eter distributions obtained from the analysis of the autocorrelation functions of intensities in panel (a). 100 101 102 103 104 105 106 0.0 0.2 0.4 0.6 0.8 1.0 g(2 ) (t ) -1 t (µs) ceugenol (% w/w) 1.0 2.0 4.0 1 10 100 1000 0 5 10 15 1 2 3 4(b) ceugenol (% w/w) 1.0 2.0 4.0 dapp h (nm) In te ns ity (% ) c eu ge no l(% w/ w) (a) Fig. 6. Results obtained by DLS for transparent liquid dispersions with a fixed amount of poloxamer 407 (concentration 7.5 %w/w) and different concentra tions of eugenol. (a) Autocorrelation functions of intensities. (b) Apparent hy drodynamic diameter distributions obtained from the analysis of the autocorrelation functions of intensities in panel (a). 0 5 10 15 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 Io ni c co nd uc tiv ity (m S/ cm ) cP407 (% w/w) ceugenol/% w/w 1 2 3 4 Fig. 7. Dependence of the ionic conductivity on the poloxamer 407 concen tration for emulsion-like dispersions with different eugenol concentration. The lines are guides for the eyes, and the error bars are smaller than the point size. A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 7 wavelength (λem) of eugenol in water at different concentrations below its solubility limit (0.246 %w/w). The fluorescence spectrum of eugenol dispersed directly in water below its solubility limit shows an emission band in the wavelength range of 320–330 nm, in agreement with that reported in the literature [60]. Encapsulation of eugenol in the form of poloxamer 407 stabilized droplets causes changes in the fluorescence emission spectrum of eugenol. Fig. 9 shows the variation of the fluorescence spectrum for homogeneous dispersions with a fixed eugenol concentration of 1 % w/w and increasing poloxamer 407 concentration. The results for samples with other eugenol concentrations were qualitatively similar. The emission spectrum of the studied dispersions shows the appearance of broad and intense emission band centered in the 400–420 nm wavelength range, indicating a clear bathochromic shift (toward red) with respect to eugenol in aqueous medium (emission band in the 320–330 nm interval). Furthermore, the band corresponding to eugenol encapsulated in Poloxamer 407 decreases in intensity with increasing copolymer concentration. This suggests the occurrence of a self-quenching phenomenon, which can be interpreted considering that increasing the copolymer concentration leads to a dispersion of eugenol forming smaller droplets, which can be considered equivalent to an in crease in eugenol confinement. This could promote cluster formation through interactions between the π-π clouds of eugenol molecules, contributing to a reduction in fluorescence intensity [61]. The effect of self-quenching as a result of confinement can be seen more clearly in Fig. 10, where the fluorescence intensity of the maximum is plotted as a function of poloxamer 407 concentration. It is noteworthy that the effect of poloxamer 407 concentration on the quenching of fluorescence emission is particularly evident at low eugenol concentrations and becomes less clear with increasing eugenol concentration. However, it is not possible to discuss the trend with increasing eugenol concentration because the compositional range corresponding to single phase dispersion is relatively narrow, i.e., the number of samples that can be evaluates is relatively small, to provide a physically sound discussion about the effect of such parameter. The ef fect of the amount of eugenol on the fluorescence emission spectrum for single-phase dispersions with a fixed amount of Poloxamer 407 (7.5 % w/w) is shown in Fig. 11. Increasing the concentration of eugenol at fixed values of copolymer concentration also leads to a self-quenching phenomenon of fluores cence emission, which is understandable considering that increasing the concentration of eugenol is expected to increase the association of eugenol in clusters. It is noteworthy that the dependencies of 300 350 400 450 0 60 120 180 240 300 0.000 0.001 0.002 ceugenol (% w/w) 1x10-3 2.5x10-3 c eu ge no l(% w/w ) λem (nm) I F ( a. u. ) Fig. 8. Fluorescence emission spectra for two solutions of eugenol in water (below the solubility limit) after excitation at 280 nm. 300 350 400 450 500 0 250 500 2 4 6 8 10 12 cP407 (% w/w) 2.5 5.0 7.5 10.0 12.5 λem (nm) I F ( a. u. ) c P40 7 (% w/w ) Fig. 9. Fluorescence emission spectra for liquid dispersions of eugenol (concentration 1 %w/w) in water stabilized with increasing poloxamer concentrations. 2 4 6 8 10 12 14 0 100 200 300 400 ceugenol (% w/w) 1 2 4 Im ax F (a .u .) cP407 (% w/w) Fig. 10. Dependence of the maximum fluorescence emission on the poloxamer 407 concentration for single-phase dispersions with fixed eugenol concentra tions. The lines are guides for the eyes, and the error bars are smaller than the point size. A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 8 fluorescence intensities and the occurrence of self-quenching phenom ena with poloxamer 407 and eugenol concentrations seem to strongly suggest the confinement of eugenol forming copolymer-stabilized droplets. This conclusion is also supported by the strong bathochromic shift observed in the emission spectra as a consequence of the intro duction of copolymer. 3.6. Modifying the phase behavior of the ternary system by thermal annealing The above discussion was focused on the study of the ternary water/ eugenol/poloxamer 407 system at room temperature. However, the thermoresponsiveness of the copolymer can help on the modification of the phase behavior of the system as a result of a thermal treatment of the emulsions. For this purpose, samples were homogenized at 65◦C for 1 h, and then they were left to cooling down at room temperature. This procedure allows obtaining a bigger compositional range where single phase homogenous systems were found. This includes two types of new emulsions, namely milky emulsion (E+++) and gel-like emulsion (E++++), and gels containing a higher amount of eugenol (see Fig. 12). The analysis of the phase diagram obtained after thermal annealing shows that the maximum eugenol amount that can be incorporated to obtain emulsion-like dispersions increases in relation to that incorpo rated for the case of the spontaneous homogenization. Moreover, the results also show that liquid-like dispersions can be obtained even for poloxamer 407 concentrations of 15 %w/w. It also noteworthy that the maximum amount of eugenol that can be incorporated in gels with a poloxamer 407 concentration of 15 %w/w is also significantly increase when the mixtures undergo the thermal annealing procedure. This can be observed clearer from the analysis of the R ratio-cP407 diagram dis played in Fig. 13. A detailed observation of the compositional maps (R ratio-cP407 di agrams) for the ternary water/eugenol/poloxamer 407 mixtures show that except for the lower temperature, the boundary between single- phase mixtures and phase separated ones occurs at higher values of R except for the lowest copolymer concentration. This latter can be probably originated because at such low concentrations the increase in the temperature does not affect the phase behavior of the copolymer, and therefore there are not structural reorganization of the system upon thermal annealing. In fact, the compositional maps in Fig. 13 does not show changes in the phase diagram for cP407≤5 %w/w with the thermal annealing. In the case of the highest polymer concentration, the increase in the temperature can affect to the hydration degree of the degree of polox amer 407 chains, leading to sol-gel and gel-sol transitions. In fact, the increase of the temperature in poloxamer solutions can induce the gelation of an aqueous micellar solution but a further increase of the temperature can push again the system to a solution-like character [62]. This latter is the cases for the gel-like structures which reduces the hy dration of the poloxamer chains. This results in the transformation of the gel-like systems to a nanodroplet dispersion which is not perturbed as a result of the cooling down process [63]. Therefore, it can be assumed that the thermal annealing results in the formation of kinetically trapped 300 350 400 450 500 550 0 80 160 240 320 400 0 1 2 3 4 ceugenol (% w/w) 1 2 4 λem (nm) I F ( a. u. ) c eu ge no l(% w/w ) Fig. 11. Fluorescence emission spectra for liquid dispersions of increasing concentrations of eugenol in water stabilized with a fixed poloxamer concentration (7.5 % w/w). Fig. 12. Phase diagram for the system water/eugenol/Poloxamer 407 prepared by using the phase inversion temperature method (65◦C for 1 h). The compo sitions of the different components are in weight fraction (wt%). The symbols indicate the different compositions studied: (i) Phase separated systems (BS); (ii) Emulsions (E: Emulsion without turbidity, E+: slightly cloudy emulsion, E++: cloudy emulsion, E+++: Milky Emulsion, E++++: Gel-like emulsion) and (iii) Gels (G: Gel without turbidity, G+: slightly cloudy gel, G++: cloudy gel). A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 9 dispersions that are not destabilized upon the decrease in the tempera ture. Simultaneously, the increase in the extension of the singe-phase region and the reduction in the compositional region corresponding to the phase-separation may be also associated with an analogous dehy dration process of the copolymer chains, which slightly reduces the hydrophilicity of the poly(ethylene oxide) blocks favoring the incorpo ration of higher eugenol amount within the nanodroplets of stable dispersions. To evaluate better the importance of the temperature and composi tion in the phase diagram, Fig. 14 represents the dependence of the maximum value of R for obtaining liquid-like dispersions and gel-like systems on the poloxamer concentration at the two temperatures. In the case of liquid-like dispersions, the maximum value of R increases as the amount of poloxamer 407 increases, independently of the temper ature, until it reaches a maximum value (around a poloxamer 407 concentration around 7.5 %w/w) and then starts to decrease until the sol-gel transition occurs. However, except for the lowest copolymer concentrations (2.5 and 5 %w/w), the higher the temperature the higher the maximum value of R, which highlight the impact of the thermal annealing in the phase behavior of the ternary system. In the case of gel- like systems, the increase of the temperature changes the dependence of the maximum value of R with the copolymer concentration, which ev idences the reduction of the compositional region corresponding to the gel formation. 3.7. Encapsulation of molecules with insecticidal and fungicidal activity in gel-like mixture In our previous publication [37] we analyzed the efficiency of poloxamer 407 stabilized eugenol in water emulsions as platforms for encapsulating a highly hydrophobic insecticide, the pyriproxyfen. Such study showed the high capacity of the emulsion-like dispersions for encapsulating hydrophobic molecules. Here, it is explored the potential application of ternary water/Eugenol/Poloxamer 407 mixtures, with compositions corresponding to the gel formation region, for the encap sulation of four different hydrophobic pesticides. Before to evaluate the capacity of gel-like structures, a calibration curve for each insecticide was done. These curves show good linearity for all the active molecules in the studied concentration range (0–1 %w/w) and can be used to evaluate the concentration of each molecule within the gel-like matrix. Fig. 15 shows the concentration of the insecticides in the four regions in which each gel sample was divided. According to the obtained results, and considering the combined error bars in each determination, the distribution of the different pesticides within gel-like samples can be considered mostly homogenous. The slight differences in the distribu tion may be originated to the difficulties of the homogenization of the hydrophobic molecules during the loading process, or to the appearance of concentration gradients during storage (6 months). It should be noted that the ability of the gel-like matrices to encapsulate the hydrophobic 0 4 8 12 16 0.0 0.5 1.0 0 4 8 12 16 R cP407 (% w/w) (b) cP407 (% w/w) (a) Fig. 13. R ratio-cP407 diagram reporting the specific compositional regions where the different types of samples are formed. (a) Spontaneous emulsification at 25ºC+thermal annealing at 65ºC+cooling down. (b) Spontaneous emulsification at 25ºC. ( ) Emulsion-like dispersions, ( ) gel-like systems, and ( ) phase- separated mixtures. Fig. 14. Maximum R values for the system water/eugenol/poloxamer 407. (left panel) Emulsion-like systems. (b) Gel-like systems. Spontaneous emulsification method at 25ºC ( ) and Thermal annealing at 65º C ( ). A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 10 molecules with insecticide activity is not dependent on the specific na ture of the molecule, reaching in all the cases load around 0.70 %w/w. Overall, the above results have pointed out that the use of thermal annealing in poloxamer-based ternary water/oil/emulsifier systems containing essential oil compounds makes it possible to optimize phase behavior and encapsulation efficiency, offering practical and eco- friendly solutions for the solubilization and delivery of poorly water- soluble active compounds. 4. Conclusions The phase behavior of the ternary water/eugenol/poloxamer 407 system reveals a subtle interplay between the concentrations of these components, leading to the formation of emulsions, gels, and phase- separated mixtures. This study provides critical insight into the compositional ranges required to maintain single-phase systems, which are essential for potential applications in the encapsulation of poorly water-soluble molecules. The results show that emulsions can be formed within certain concentration ranges of Poloxamer 407 and eugenol. When the concentration of eugenol is increased beyond this range, the mixtures tend to phase separate due to the present of an insufficient quantity of poloxamer to stabilize the eugenol droplets. Conversely, increasing the concentration of Poloxamer 407 leads to gel formation, especially at higher copolymer levels combined with eugenol concen trations between 1 % and 8 % w/w. In addition, visual and physical changes observed in the mixtures, such as color transitions from pale yellow to strong orange/brown, increasing turbidity with higher eugenol content, or changes in droplet size and ionic conductivity, further support the phase transitions. These observations indicate that as the eugenol content increases, the samples shift towards phase separa tion, mainly due to the limited availability of poloxamer to adequately stabilize the dispersed oil phase. On the other hand, as the poloxamer concentration is increased, the viscosity of the mixture increases significantly, promoting gel formation. This transition is attributed to the sharp increase in the number of eugenol-containing aggregates, which eventually leads to a percolated, densely packed system, resulting in a gel-like state. The combined analysis of the whole set of results shows that maintaining a minimum poloxamer concentration is crucial to ensure the dispersion of eugenol in water, and the importance of precise compositional control to develop stable single-phase systems. Moreover, this work has shown that a careful control of the thermal history of the ternary water/eugenol/poloxamer system allows to modulate the phase behavior of the systems, which provides the bases to extend the compositional ranges for the appearance of specific phases or to obtain new ones. Last but not least, gel-like dispersions have shown a high capacity to encapsulate different hydrophobic pesticides. In summary, the phase behavior of water/eugenol/poloxamer 407 systems is highly dependent on the precise balance between the con centration of the components and the thermal history of the system. In this work, it has primarily studied the phase behavior of the ternary water/eugenol/poloxamer 407 system at room temperature. However, the thermoresponsive nature of the poloxamer 407 has provided an opportunity to modify the phase behavior through thermal annealing. This allows expanding the compositional range over which homoge neous single-phase systems are observed, offing a strategy to increase the maximum amount of eugenol that can be incorporated into emulsion-like dispersions compared to those formed via spontaneous homogenization, which can be important to increase the bioavailabity of the eugenol. To the best of our knowledge, this aspect has not been systematically focused in the literature, opening an important field of research due to its potential technological and industrial impact. Moreover, gel-like samples haven been found as effective carriers for hydrophobic insecticides and fungicides, which makes of the ternary offering a promising approach for encapsulation and potential controlled release applications in agricultural or other relevant fields, expanding the potential range of applications of the studied ternary system and their analogous. Therefore, this research underscores the need for careful formulation to achieve stable single-phase systems that Fig. 15. Distribution of each active molecule in the four zones (Lower, Lower central, Upper central and Upper) of the syringe containing the gel formulation with different pesticide. (a) Tebuconazole, (b) Pyriproxyfen, (c) Permethrin and (d) Lufenuron. Each bar represents the average value of four replicates and the vertical lines represents the standard deviation. The dotted line represents the average concentration of the active ingredient in the syringe. A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 11 can effectively encapsulate poorly water-soluble molecules. The results provide a basis for further exploration and optimization of these ternary systems for various applications, including pest control, where stable emulsions or gels are required. CRediT authorship contribution statement Luciana Rocha: Writing – review & editing, Resources. Pamela Banegas: Writing – review & editing. Julia Monge-Corredor: Writing – review & editing, Investigation. Alejandro Lucia: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investiga tion, Funding acquisition, Formal analysis, Data curation, Conceptuali zation. Eduardo Guzman: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Meth odology, Investigation, Funding acquisition, Conceptualization. Ramón G. Rubio: Investigation, Supervision, Writing – review & editing. Belén Arcos-Álvarez: Writing – review & editing, Methodology, Investigation. Agustina Fañani: Writing – review & editing, Methodology, Investi gation, Formal analysis, Data curation. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Data availability Data will be made available on request. Acknowledgements This work in Argentina was funded by Agencia Nacional de Promoción Científica y Técnica (ANPCyT): PICT-2021-GRF-TI-00704. Also, the work in Madrid was supported under the grant PID2023- 147156NB-I00, funded by MCIN/AEI/10.13039/501100011033 (Spain) and the European Innovative Training Network-Marie Sklo dowska-Curie Action NanoPaInt (grant agreement 955612), funded by the E.U. The Centro de Espectroscopía y Correlación (CAI de Técnicas Químicas) of the Universidad Complutense de Madrid is acknowledged for the use of their facilities. References [1] M. Ragaei, A.H. Sabry, Nanotechnology for insect pest control, Int. J. Sci. Environ. Tech. 3 (2014) 528–545. [2] D.J. McClements, Food Emulsions: Principles, Practices, and Techniques, third ed., CRC Press, 2015. [3] E. Guzmán, A. Lucia, Essential oils and their individual components in cosmetic products, Cosmetics 8 (2021) 114, https://doi.org/10.3390/cosmetics8040114. [4] T.N. da Silva, S.A. Cardoso, T.N. Barradas, Chapter 21 - Nanostructured pharmaceutical formulations for topical application of clove oil and eugenol, in: Clove (Syzygium aromaticum), Ramadan, M. F. Ed., Academic Press, 2022, pp. 363–403. [5] J.-H. Wang, F. Kong, B.-F. Liu, S.-N. Zhuo, N.-Q. Ren, H.-Y. Ren, Enhanced photocatalytic degradation of diclofenac by UiO-66/MgAl-LDH: excellent performances and mechanisms, 10.1039/D4EN00266K, Environ. Sci. Nano 11 (8) (2024) 3286–3293, https://doi.org/10.1039/D4EN00266K. [6] J.-H. Wang, F. Kong, B.-F. Liu, S.-N. Zhuo, N.-Q. Ren, H.-Y. Ren, Photogenerated carrier-accelerated 3D mesh-NH2 functionalized Zr-metal organic framework/ MgAl-type hydrotalcite composites attacking diclofenac, Sep. Purif. Technol. 354 (2025) 128839, https://doi.org/10.1016/j.seppur.2024.128839. [7] E.V. Batrakova, T.K. Bronich, J.A. Vetro, A.V. Kabanov, Polymer micelles as drug carriers, Nanoparticulates Drug Carr. (2006) 57–93, https://doi.org/10.1142/ 9781860949074_0005. [8] E.V. Batrakova, A.V. Kabanov, Pluronic block copolymers: evolution of drug delivery concept from inert nanocarriers to biological response modifiers, J. Control. Release 130 (2008) 98–106, https://doi.org/10.1016/j. jconrel.2008.04.013. [9] S. Kim, K. Park, Polymer micelles for drug delivery, in: A.S. Narang, R.I. Mahato (Eds.), Targeted Delivery of Small and Macromolecular Drugs, CRC Press, Boca Ratón, United States of America, 2010, pp. 513–551. [10] K.T. Savjani, A.K. Gajjar, J.K. Savjani, Drug solubility: importance and enhancement techniques, ISRN Pharm. (2012) 195727, https://doi.org/10.5402/ 2012/195727. [11] K.B. Sutradhar, L. Amin, Nanoemulsions: increasing possibilities in drug delivery, Eur. J. Nanomed. 5 (2013) 97–110, https://doi.org/10.1515/ejnm-2013-0001. [12] T.N. Barradas, J.P. Senna, S.A. Cardoso, S. Nicoli, C. Padula, P. Santi, F. Rossi, K. G. de Holanda e Silva, Manzur, C. R. E. Hydrogel-thickened nanoemulsions based on essential oils for topical delivery of psoralen: permeation and stability studies, Eur. J. Pharm. Biopharm. 116 (2017) 38–50, https://doi.org/10.1016/j. ejpb.2016.11.018. [13] D.J. Mc Clements, S.M. Jafari, General aspects of nanoemulsions and their formulation. in: Nanoemulsions, Elsevier, 2018, pp. 3–20. [14] E. Guzmán, L. Fernández-Peña, L. Rossi, M. Bouvier, F. Ortega, R.G. Rubio, Nanoemulsions for the encapsulation of hydrophobic actives, Cosmetics 8 (2021) 45, https://doi.org/10.3390/cosmetics8020045. [15] N. Sharma, S. Mishra, S. Sharma, R.D. Deshpande, R.K. Sharma, Preparation and optimization of nanoemulsions for targeting drug delivery, Int. J. Drug Dev. Res. 5 (2013) 37–48. [16] H. Yardimci, B. Chung, J.L. Harden, R.L. Leheny, Phase behavior and local dynamics of concentrated triblock copolymer micelles, J. Chem. Phys. 123 (2005) 244–908, https://doi.org/10.1063/1.2132278. [17] R. Basak, R. Bandyopadhyay, Encapsulation of hydrophobic drugs in Pluronic F127 micelles: effects of drug hydrophobicity, solution temperature, and pH, Langmuir 29 (2013) 4350–4356, https://doi.org/10.1021/la304836e. [18] I.R. Schmolka, Artificial skin 1. Preparation and properties of Pluronic F-127 gels for treatment of burns, J. Biomed. Mater. Res. 6 (1972) 571–582, https://doi.org/ 10.1002/jbm.820060609. [19] L.E. Bromberg, Ron, E. S. Temperature-responsive gels and thermogelling polymer matrices for protein and peptide delivery, Adv. Drug Deliv. Rev. 31 (1998) 197–221, https://doi.org/10.1016/S0169-409X(97)00121-X. [20] P.K. Sharma, S.R. Bhatia, Effect of anti-inflammatories on Pluronic® F127: micellar assembly, gelation and partitioning, Int. J. Pharm. 278 (2004) 361–377, https:// doi.org/10.1016/j.ijpharm.2004.03.029. [21] G. Wanka, H. Hoffmann, W. Ulbricht, Phase diagrams and aggregation behavior of poly(oxyethylene)– poly(oxypropylene)–poly(oxyethylene) triblock copolymers in aqueous solutions, Macromolecules 27 (1994) 4145–4159, https://doi.org/ 10.1021/ma00093a016. [22] M.J. Song, D.S. Lee, J.H. Ahn, D.J. Kim, S.C. Kim, Dielectric behavior during sol-gel transition of PEO–PPO–PEO triblock copolymer aqueous solution. Polym. Bull. 43 (2000) 497–504. [23] M. Bohorquez, C. Koch, T. Trygstad, N. Pandit, A study of the temperature- dependent micellization of pluronic F127, J. Colloid Interface Sci. 216 (1999) 34–40, https://doi.org/10.1006/jcis.1999.6273. [24] A. Lucia, P.G. Argudo, E. Guzmán, R.G. Rubio, F. Ortega, Formation of surfactant free microemulsions in the ternary system water/eugenol/ethanol, Colloids Surf. A. 521 (2017) 133–140, https://doi.org/10.1016/j.colsurfa.2016.04.062. [25] M.R. Morshedloo, L.E. Craker, A. Salami, V. Nazeri, H. Sang, F. Maggi, Effect of prolonged water stress on essential oil content, compositions and gene expression patterns of mono-and sesquiterpene synthesis in two oregano (Origanum vulgare L.) subspecies, Plant Physiol. Biochem. 111 (2017) 119–128, https://doi.org/ 10.1016/j.plaphy.2016.11.023. [26] S. Miresmailli, M.B. Isman, Botanical insecticides inspired by plant–herbivore chemical interactions, Trends Plant Sci. 19 (2014) 29–35, https://doi.org/ 10.1016/j.tplants.2013.10.002. [27] T.N. Barradas, K.G. de Holanda e Silva, Nanoemulsions of essential oils to improve solubility, stability and permeability: a review, Environ. Chem. Lett. 19 (2021) 1153–1171, https://doi.org/10.1007/s10311-020-01142-2. [28] M.G. Goñi, S.I. Roura, A.G. Ponce, M.R. Moreira, Clove (Syzygium aromaticum) oils. in: Essential oIls in Food Preservation, Flavor and Safety, Preedy, V. R., Ed., Academic Press, 2016. [29] L. Jirovetz, G. Buchbauer, I. Stoilova, A. Stoyanova, A. Krastanov, E. Schmidt, Chemical composition and antioxidant properties of clove leaf essential oil, J. Agric. Food Chem. 54 (2006) 6303–6307, https://doi.org/10.1021/jf060608c. [30] K. Chaieb, H. Hajlaoui, T. Zmantar, A.B. Kahla-Nakbi, M. Rouabhia, K. Mahdouani, A. Bakhrouf, The chemical composition and biological activity of clove essential oil, Eugenia caryophyllata (Syzigium aromaticum L. Myrtaceae): a short review, Phytother Res. 21 (2007) 501–506, https://doi.org/10.1002/ptr.2124. [31] N. Faraone, N.K. Hillier, G.C. Cutler, Plant essential oils synergize and antagonize toxicity of different conventional insecticides against Myzus persicae (Hemiptera: Aphididae), PLoS One 10 (2015) e0127774, https://doi.org/10.1371/journal. pone.0127774. [32] E.J. Norris, A.D. Gross, B.M. Dunphy, S. Bessette, L. Bartholomay, J.R. Coats, Comparison of the insecticidal characteristics of commercially available plant essential oils against Aedes aegypti and Anopheles gambiae (Diptera: Culicidae), J. Med. Entomol. 52 (2015) 993–1002, https://doi.org/10.1093/jme/tjv090. [33] A.D. Gross, E.J. Norris, M.J. Kimber, L.C. Bartholomay, J.R. Coats, Essential oils enhance the toxicity of permethrin against Aedes aegypti and Anopheles gambiae, Med. Vet. Entomol. 31 (2017) 55–62, https://doi.org/10.1111/mve.12197. [34] E.J. Norris, J.B. Johnson, A.D. Gross, L.C. Bartholomay, J.R. Coats, Plant essential oils enhance diverse pyrethroids against multiple strains of mosquitoes and inhibit detoxification enzyme processes, Insects 9 (2018) 132, https://doi.org/10.3390/ insects9040132. A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 12 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref1 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref1 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref2 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref2 https://doi.org/10.3390/cosmetics8040114 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref4 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref4 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref4 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref4 https://doi.org/10.1039/D4EN00266K https://doi.org/10.1016/j.seppur.2024.128839 https://doi.org/10.1142/9781860949074_0005 https://doi.org/10.1142/9781860949074_0005 https://doi.org/10.1016/j.jconrel.2008.04.013 https://doi.org/10.1016/j.jconrel.2008.04.013 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref9 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref9 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref9 https://doi.org/10.5402/2012/195727 https://doi.org/10.5402/2012/195727 https://doi.org/10.1515/ejnm-2013-0001 https://doi.org/10.1016/j.ejpb.2016.11.018 https://doi.org/10.1016/j.ejpb.2016.11.018 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref13 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref13 https://doi.org/10.3390/cosmetics8020045 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref15 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref15 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref15 https://doi.org/10.1063/1.2132278 https://doi.org/10.1021/la304836e https://doi.org/10.1002/jbm.820060609 https://doi.org/10.1002/jbm.820060609 https://doi.org/10.1016/S0169-409X(97)00121-X https://doi.org/10.1016/j.ijpharm.2004.03.029 https://doi.org/10.1016/j.ijpharm.2004.03.029 https://doi.org/10.1021/ma00093a016 https://doi.org/10.1021/ma00093a016 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref22 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref22 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref22 https://doi.org/10.1006/jcis.1999.6273 https://doi.org/10.1016/j.colsurfa.2016.04.062 https://doi.org/10.1016/j.plaphy.2016.11.023 https://doi.org/10.1016/j.plaphy.2016.11.023 https://doi.org/10.1016/j.tplants.2013.10.002 https://doi.org/10.1016/j.tplants.2013.10.002 https://doi.org/10.1007/s10311-020-01142-2 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref28 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref28 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref28 https://doi.org/10.1021/jf060608c https://doi.org/10.1002/ptr.2124 https://doi.org/10.1371/journal.pone.0127774 https://doi.org/10.1371/journal.pone.0127774 https://doi.org/10.1093/jme/tjv090 https://doi.org/10.1111/mve.12197 https://doi.org/10.3390/insects9040132 https://doi.org/10.3390/insects9040132 [35] F. Tong, J. Bloomquist, Plant essential oils affect the toxicities of carbaryl and permethrin against Aedes aegypti (Diptera: Culicidae). J. Med. Entomol. Suppl. 50 (2013) 826–832, https://doi.org/10.1603/ME13002. [36] M. Cáceres, E. Guzmán, A. Alvarez-Costa, F. Ortega, R.G. Rubio, C. Coviella, P. L. Santo Orihuela, C.V. Vassena, A. Lucia, Surfactantless emulsions containing eugenol for imidacloprid solubilization: physicochemical characterization and toxicity against insecticide-resistant Cimex lectularius, Molecules 25 (2020) 2290, https://doi.org/10.3390/molecules25102290. [37] A. Lucia, E. Guzmán, R.G. Rubio, F. Ortega, Enhanced solubilization of an insect juvenile hormone (JH) mimetic (piryproxyfen) using eugenol in water nanoemulsions stabilized by a triblock copolymer of poly (ethylenglycol) and poly (propilenglycol), Colloids Surf. A 606 (2020) 125513, https://doi.org/10.1016/j. colsurfa.2020.125513. [38] A.C. Toloza, E. Sosa-Quiroga, A. Fañani, A. Puente-Santamaria, E. Guzmán, E. Martínez, A. Lucia, Effectiveness and chemical insights: Exploring interactions between nanomicelles and monoterpenoids for head lice treatment, Pestic. Biochem. Physiol. 201 (2024) 105886, https://doi.org/10.1016/j. pestbp.2024.105886. [39] A. Lucia, M. Murace, G. Sartor, G. Keil, R. Cámera, R.G. Rubio, E. Guzmán, Oil in water nanoemulsions loaded with tebuconazole for populus wood protection against white-and brown-rot fungi, Forests 12 (2021) 1234, https://doi.org/ 10.3390/f12091234. [40] Denler Zhang, Aikens Friberg, Phase diagram and emulsion stability of surfactant–fragrance systems, Int. J. Cosmet. Sci. 22 (2) (2000) 105–119, https:// doi.org/10.1046/j.1467-2494.2000.00007.x. [41] M. Artiga-Artigas, M.I. Guerra-Rosas, J. Morales-Castro, L. Salvia-Trujillo, O. Martín-Belloso, Influence of essential oils and pectin on nanoemulsion formulation: a ternary phase experimental approach, Food Hydrocoll. 81 (2018) 209–219, https://doi.org/10.1016/j.foodhyd.2018.03.001. [42] S. Zhang, M. Zhang, Z. Fang, Y. Liu, Preparation and characterization of blended cloves/cinnamon essential oil nanoemulsions, LWT 75 (2017) 316–322, https:// doi.org/10.1016/j.lwt.2016.08.046. [43] A. Perazzo, V. Preziosi, S. Guido, Phase inversion emulsification: current understanding and applications, Adv. Colloid Interface Sci. 222 (2015) 581–599, https://doi.org/10.1016/j.cis.2015.01.001. [44] T.D.T. Vinh, L.T.M. Hien, D.T.A. Dao, Formulation of black pepper (Piper nigrum L.) essential oil nano-emulsion via phase inversion temperature method, Food Sci. Nutr. 8 (4) (2020) 1741–1752, https://doi.org/10.1002/fsn3.1422. [45] E. Haba, S. Bouhdid, N. Torrego-Solana, A.M. Marqués, M.J. Espuny, M.J. García- Celma, A. Manresa, Rhamnolipids as emulsifying agents for essential oil formulations: antimicrobial effect against Candida albicans and methicillin- resistant Staphylococcus aureus, Int. J. Pharm. 476 (1) (2014) 134–141, https:// doi.org/10.1016/j.ijpharm.2014.09.039. [46] A. Lucia, C. Girard, M. Fanucce, C. Coviella, R.G. Rubio, F. Ortega, E. Guzmán, Development of an environmentally friendly larvicidal formulation based on essential oil compound blend to control aedes aegypti larvae: correlations between physicochemical properties and insecticidal activity, ACS Sustain. Chem. Eng. 8 (29) (2020) 10995–11006, https://doi.org/10.1021/acssuschemeng.0c03778. [47] H. Gorjian, P. Mihankhah, N.G. Khaligh, Influence of tween nature and type on physicochemical properties and stability of spearmint essential oil (Mentha spicata L.) stabilized with basil seed mucilage nanoemulsion, J. Mol. Liq. 359 (2022) 119379, https://doi.org/10.1016/j.molliq.2022.119379. [48] H. Li, G.E. Yu, C. Price, C. Booth, E. Hecht, H. Hoffmann, Concentrated aqueous micellar solutions of diblock copoly(oxyethylene/oxybutylene) E41B8: a study of pase behavior, Macromolecules 30 (1997) 1347–1354, https://doi.org/10.1021/ ma961520a. [49] M.V. Bentley, J.M. Marchetti, N. Ricardo, Z. Ali-Abi, J.H. Collett, Influence of lecithin on some physical chemical properties of poloxamer gels: rheological, microscopic and in vitro permeation studies, Int. J. Pharm. 193 (1999) 49–55, https://doi.org/10.1016/S0378-5173(99)00313-0. [50] K.W. Kwon, M.J. Park, J. Hwang, K. Char, Effects of alcohol addition on gelation in aqueous solution of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymer, Polym. J. 33 (2001) 404–410, https://doi.org/10.1295/ polymj.33.404. [51] L. Fernández-Peña, S. Gutiérrez-Muro, E. Guzmán, A. Lucia, F. Ortega, G.R. Rubio, Oil-in-water microemulsions for thymol solubilization, Colloids Interfaces 3 (2019) 64, https://doi.org/10.3390/colloids3040064. [52] A. Lucia, A.C. Toloza, E. Guzmán, F. Ortega, R.G. Rubio, Novel polymeric micelles for insect pest control: encapsulation of essential oil monoterpenes inside a triblock copolymer shell for head lice control, PeerJ 5 (2017) e3171, https://doi.org/ 10.7717/peerj.3171. [53] H.B. Wang, Y.J. Zhang, X. Xiao, D. Jin, N.J. Zhao, G.F. Yin, L.Q. Guo, W.Q. Liu, Excitation-emission fluorescence characterization study of the three phenolic compounds, Spectrosc. Spectr. Anal. 30 (2010) 1271–1274, https://doi.org/ 10.3964/j.issn.1000-0593(2010)05-1271-04. [54] N. Sánchez-Arribas, E. Guzmán, A. Lucia, A.C. Toloza, M.G. Velarde, F. Ortega, R. G. Rubio, Environmentally friendly platforms for encapsulation of an essential oil: fabrication, characterization and application in pests control, Colloids Surf. A (555) (2018) 473–481, https://doi.org/10.1016/j.colsurfa.2018.07.028. [55] M. Elmowafy, A. Musa, T.S. Alnusaire, K. Shalaby, M.M.A. Fouda, A. Salama, M. M. Al-Sanea, M.A. Abdelgawad, M. Gamal, S.A. Fouad, Olive oil/pluronic oleogels for skin delivery of quercetin: in vitro characterization and ex vivo skin permeability, Polymers 13 (11) (2021) 1808, https://doi.org/10.3390/ polym13111808. [56] S. Sugumar, S. Singh, A. Mukherjee, et al., Nanoemulsion of orange oil with non ionic surfactant produced emulsion using ultrasonication technique: evaluating against food spoilage yeast, Appl. Nanosci. 6 (2016) 113–120, https://doi.org/ 10.1007/s13204-015-0412-z. [57] B.J. Berne, R. Pecora, Dynamic Light Scattering: With Applications to Chemistry. Biology, and Physics, Dover Publications, Inc, Mineola, NY, USA, 1976. [58] R. Barreiro-Iglesias, C. Alvarez-Lorenzo, A. Concheiro, Poly (acrylic acid) microgels (carbopol® 934)/surfactant interactions in aqueous media Part I: nonionic surfactants, Int. J. Pharm. 258 (2003) 165–177, https://doi.org/10.1016/S0378- 5173(03)00181-9. [59] G.Z. Abdullah, M.F. Abdulkarim, I.M. Salman, O.Z. Ameer, M. Chitneni, E. S. Mahdi, M.F. Yam, S. Hameem, M. Basri, M.A. Sattar, A.M. Noor, Stability studies of nano-scaled emulsions containing ibuprofen for topical delivery, Int. J. Drug Dev. 3 (2011) 74–82. [60] S. Bi, L. Yan, Y. Wang, B. Pang, T. Wang, Spectroscopic study on the interaction of eugenol with salmon sperm DNA in vitro, J. Lumin. 132 (2012) 2355–2360, https://doi.org/10.1016/j.jlumin.2012.04.029. [61] M.J. Hollamby, A.E. Danks, Z. Schnepp, S.E. Rogers, S.R. Hart, T. Nakanishi, Fluorescent liquid pyrene derivative-in-water microemulsions, Chem. Commun. 52 (2016) 7344–7347, https://doi.org/10.1039/C6CC01517D. [62] C.F. Lee, M.R. Wang, T.L. Lin, C.H. Yang, L.J. Chen, Dynamic behavior of the structural phase transition of hydrogel formation induced by temperature ramp and addition of ibuprofen, Langmuir 36 (2020) 8929–8938, https://doi.org/ 10.1021/acs.langmuir.0c01437. [63] Y. Li, T. Shi, Z. Sun, L. An, Q. Huang, Investigation of sol− gel transition in Pluronic F127/D2O solutions using a combination of small-angle neutron scattering and Monte Carlo simulation, J. Phys. Chem. B 110 (2006) 26424–26429, https://doi. org/10.1021/jp066019r. A. Fañani et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 704 (2025) 135474 13 https://doi.org/10.1603/ME13002 https://doi.org/10.3390/molecules25102290 https://doi.org/10.1016/j.colsurfa.2020.125513 https://doi.org/10.1016/j.colsurfa.2020.125513 https://doi.org/10.1016/j.pestbp.2024.105886 https://doi.org/10.1016/j.pestbp.2024.105886 https://doi.org/10.3390/f12091234 https://doi.org/10.3390/f12091234 https://doi.org/10.1046/j.1467-2494.2000.00007.x https://doi.org/10.1046/j.1467-2494.2000.00007.x https://doi.org/10.1016/j.foodhyd.2018.03.001 https://doi.org/10.1016/j.lwt.2016.08.046 https://doi.org/10.1016/j.lwt.2016.08.046 https://doi.org/10.1016/j.cis.2015.01.001 https://doi.org/10.1002/fsn3.1422 https://doi.org/10.1016/j.ijpharm.2014.09.039 https://doi.org/10.1016/j.ijpharm.2014.09.039 https://doi.org/10.1021/acssuschemeng.0c03778 https://doi.org/10.1016/j.molliq.2022.119379 https://doi.org/10.1021/ma961520a https://doi.org/10.1021/ma961520a https://doi.org/10.1016/S0378-5173(99)00313-0 https://doi.org/10.1295/polymj.33.404 https://doi.org/10.1295/polymj.33.404 https://doi.org/10.3390/colloids3040064 https://doi.org/10.7717/peerj.3171 https://doi.org/10.7717/peerj.3171 https://doi.org/10.3964/j.issn.1000-0593(2010)05-1271-04 https://doi.org/10.3964/j.issn.1000-0593(2010)05-1271-04 https://doi.org/10.1016/j.colsurfa.2018.07.028 https://doi.org/10.3390/polym13111808 https://doi.org/10.3390/polym13111808 https://doi.org/10.1007/s13204-015-0412-z https://doi.org/10.1007/s13204-015-0412-z http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref57 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref57 https://doi.org/10.1016/S0378-5173(03)00181-9 https://doi.org/10.1016/S0378-5173(03)00181-9 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref59 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref59 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref59 http://refhub.elsevier.com/S0927-7757(24)02338-0/sbref59 https://doi.org/10.1016/j.jlumin.2012.04.029 https://doi.org/10.1039/C6CC01517D https://doi.org/10.1021/acs.langmuir.0c01437 https://doi.org/10.1021/acs.langmuir.0c01437 https://doi.org/10.1021/jp066019r https://doi.org/10.1021/jp066019r Stabilization of gels and emulsions in the ternary water/eugenol/poloxamer 407-system: Physicochemical characterization and ... 1 Introduction 2 Materials and methods 2.1 Chemicals 2.2 Preparation and classification of mixtures containing eugenol and P407 2.3 Evaluation of the sample nature 2.4 Characterization techniques 2.5 Encapsulation of pesticides in gel-like mixtures 3 Results and discussion 3.1 Phase diagram of water/Eugenol/poloxamer 407 system obtained using spontaneous emulsification at 25ºC 3.2 Compositional control of the phase formation 3.3 Size characterization of the dispersed droplets 3.4 Conductimetric study of emulsion-like dispersions 3.5 Spectroscopy evidence of the confinement of eugenol within poloxamer 407 stabilized nanodroplets 3.6 Modifying the phase behavior of the ternary system by thermal annealing 3.7 Encapsulation of molecules with insecticidal and fungicidal activity in gel-like mixture 4 Conclusions CRediT authorship contribution statement Declaration of Competing Interest Data availability Acknowledgements References