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Sheets of poly(lactic acid) (PLA) and thermoplastic starch (TPS) with citric and adipic acid additives were produced through a calendering–extrusion process at pilot scale, and its mechanical, barrier, thermal, and morphological characteristics were determined. According to the micrographs, citric acid improved the fragmentation and dispersion of starch granules by facilitating interactions with PLA chains and increasing interfacial adhesion. Citric acid also induced a significant increase in the tensile strength and elongation at break, reducing water vapor permeability, increasing crystallinity, but decreased slightly the thermal stability. Adipic acid did not demonstrate the same efficiency, even when mixed with citric acid.

This work describes the drug release profile and the initial burst release from covalent hydrogel nanocomposites composed of pectin, hydroxyethyl methacrylate (HEMA) and titania (TiO2). Vitamin B12 (Vit-B12), a highly water-soluble substance, was used as a model drug. We studied the water transport profiles over a wide pH range, the moduli of elasticity (E), the morphological properties and the Vit-B12 release kinetics from these hydrogels. The initial release burst was reduced by crosslinking titania with vinylated pectin and HEMA. A reduction of up to ca. 60% was observed when compared with pure pectin/HEMA hydrogel. To gain insight into the burst release phenomenon, the experimental data were adjusted to diffusive-based models that include a rate constant of release (k). A decrease in the values of k was related to a reduction in the burst effect. The release mechanism of Vit-B12 from the pure hydrogels was governed by both Fickian diffusion and macromolecular relaxation, which are the driving forces for release. Upon addition of titania, the contribution of macromolecular relaxation to the release was minimized, suggesting a tendency towards Fickian diffusion. Furthermore, titania played a significant role in improving mechanical properties. Hydrogel nanocomposites showed a marked increase in E compared with pure hydrogels. This increase was found to be the result of an apparent increment in the cross-linking density, owing to chemical bonds of titania with the hydrogel. The proposed materials were demonstrated to be biocompatible with cells, showing good pharmacological potential.

This work describes the preparation of thin film nanocomposites of silver nanoparticles (AgNPs) embedded in a copolymer matrix of poly(ethylene glycol) diacrylate (PEGDA) and triethylene glycol dimethacrylate (TEGDMA). The films were produced by UV-induced chemical reduction of Ag + ions using (1,5-cyclooctadiene)(hexafluoro-acetylacetonate)silver(I) as Ag precursor, together with the photopolymerization of PEGDA and TEGDMA using 2-hydroxy-2-methylpropiophenone as photoinitiator. The average size of AgNPs increased from ca. 6 nm to ca. 15 nm with 1 h heating at 180 °C because of the nanoparticle coalescence, which causes an important change on the surface morphology. Small details were observed on the nanocomposite surface and became more evident on the heated film, as demonstrated by SEM. The morphology change is the result of migration of AgNPs towards the surface and was very clear owing to thin thickness of the nanocomposite (ca. 30 μm). This nanoparticle relocation was also observed by TEM. This work offers a material that can provide important applications in which surface properties are relevant such as sensors and actuators.

We developed a pH-responsive, hydrogel based on poly(ethylene glycol) (PEG) covalently cross-linked with acrylic acid and N′,N′-dimethylacrylamide along with acid-labile groups. In the hydrogel, PEG plays a role as the key constituent. If its chains break, the polymer networks are destroyed. The pharmacological potential of these hydrogels were demonstrated by determining their water transport profile, modulus of elasticity, and cytotoxicity assay. The hydrogels showed a pseudo-Fickian behavior, a transport mechanism that occurs when the diffusion coefficient changes with the time and the swelling equilibrium is never fully reached. At pH 2, the PEG-richer hydrogels degraded and the scanning electron microscopy (SEM) images illustrated less-defined shapes than at pH 7 and 10. This morphological characteristic results of the hydrogel deconstruction owing to cleavage of ether bonds of the PEG chains unmaking its 3D polymer network. The proposed hydrogels were shown to be compatible to cells, indicating acceptable biocompatibility and an appropriate level of security for use in the biological environments. Furthermore, they showed structural changes in their polymer network in response to pH, which is an important characteristic for stimuli-triggered release of guest molecules.

Magnetic hybrid colloidal particles can be characterized using various techniques and numerous tools leading generally to particles size, size distribution, and electrokinetic properties. However, the chemical composition of these hybrid particles can be estimated using thermal gravimetric analysis (TGA). More interestingly, the combination of this quantitative technique with the magnetization measurement leads not only to chemical composition but also to the overall polymerization conversion and more precisely to the polymerization conversion on the seed particles. In fact, the TGA performed on dried magnetic particles leads to exact organic/inorganic chemical composition. Regarding the magnetization, the amount of magnetic material can be deduced, and consequently, the amount of non-magnetic material can be also estimated. Thus, TGA and magnetization measurements are considered as complementary techniques for characterization of magnetic hybrid colloidal particles.

Micrometer magnetic hybrid particles are of great interest in biomedical field, and various morphologies have been prepared via encapsulation processes. Regarding submicron, only few processes have been investigated and the most recent one leading to highly magnetic submicron magnetic hybrid particles is based on oil in water magnetic emulsion (MES) transformation. The encapsulation of magnetic iron oxide nanoparticles forming oil in water MES was investigated using different styrene/cross-linker divinylbenzene volume ratio in the presence of potassium persulfate initiator. The encapsulation performed in this work is basically conducted by using well-defined oil in water MES as a seed in radical emulsion polymerization. The chemical composition, morphology, iron oxide content, magnetic properties, electrokinetic properties, particle size, and size distribution of the prepared magnetic hybrid particles were examined using various techniques. The desired perfect magnetic core and polymer shell morphology were successfully obtained, and the final magnetic hybrid particles are superparamagnetic in nature and exhibit high iron oxide content (64 wt %). Copyright © 2015 John Wiley & Sons, Ltd.

This work describes a rapid and direct synthesis strategy for semi-crystalline TiO 2 nanoparticles by scCO 2 antisolvent expansion of sol–gel precursor. The scCO 2 -based nanoparticles were produced by the hydrolysis reaction of titanium (IV) isopropoxide in an aqueous medium. The successful synthesis of these nanoparticles was associated to the formation of a scCO 2 -induced one-phase system, which allowed both a rapid reaction of the precursor and an efficient drying (by expansion onto scCO 2 ) of the product. The nanoparticles showed a well-marked amorphous-to-crystalline transition as submitted to thermocycling. The BET analysis of TiO 2 nanoparticles showed a surface area of 418.5 m 2 g −1 and the DLS curve indicated an average size of 316.7±2.7 nm. The use of scCO 2 expansion technology as a reaction medium allowed the synthesis of a nanomaterial with a large surface area, making it attractive for use in adsorption process. The obtained material is free of organic solvents, catalysts or surfactants, and does not require further purification. This study offers not only an environmentally friendly product, but also a simple approach which does not need particular skills.

Well-defined polycaprolactone (PCL) nanoparticles loaded with progesterone (P4) were obtained by scCO2 antisolvent expansion of emulsions as a drying strategy. PCL nanoparticles with an average diameter of 82 nm were formed by the emulsification of an ethyl acetate–water mixture containing P4 and poly(vinyl alcohol) (PVA) as the stabilizing agent under ultrasonic irradiation. Emulsion particles were dried in scCO2 and the results were compared with drying at ambient conditions. The scCO2 expansion-dried PCL nanoparticles showed a smaller average diameter and the dynamic light scattering (DLS) analysis revealed a narrower particle size distribution when compared to the diameter of nanoparticles formed with the conventional process (174 nm). The use of scCO2 expansion technology as a drying strategy for the production of PCL nanoparticles with a narrow size distribution for P4 delivery represents an improvement over the conventional drying processes.

The objective of this work was to investigate the application of supercritical carbon dioxide as antisolvent for the co-precipitation of  -carotene and poly(hydroxybutirate-co-hydroxyvalerate) (PHBV) with dichloromethane as or- ganic solvent. For this purpose, the concentrations of  -carotene (1 to 8 mg.cm -3 ) and PHBV (20 to 40 mg.cm -3 ) in the or- ganic solution were varied keeping fixed temperature at 313 K, pressure at 8 MPa, solution flow rate at 1 cm 3 .min -1 and antisolvent flow rate at 39 g.min -1 . The morphology of co-precipitated particles were spherical with very irregular and po- rous surface for some conditions and very smooth surfaces for others as verified by micrographs of scanning electronic microscopy (SEM). Results show that it is possible to achieve encapsulation efficiency values as high as 35 % just ma- nipulating the concentration ratio of solute to polymer in organic solution. The methodology adopted for the quantification of  -carotene encapsulated was demonstrated to be adequate.

In this work the vapor–liquid equilibrium for the {CO2(1) + dichloromethane(2) + medroxyprogesterone(3)} system were measured for different concentrations of medroxyprogesterone in dichloromethane (0.01 g mL−1 and 0.02 g mL−1) at temperatures ranging from (303 to 333) K and pressure up to 8.6 MPa. The experimental data were obtained using a visual synthetic static method employing a variable volume cell. The liquid–vapor transitions were classified as a bubble points and dew points in the presence or absence of solid phase. The experimental vapor–liquid equilibrium data were satisfactory correlated using the Peng–Robinson equation of state with a quadratic mixing rule.

This work is aimed at providing an easy and quick determination of the biodiesel products using near infrared spectroscopy (NIR) by combination with the multivariate calibration in the analysis of (liquid + liquid) equilibrium (LLE) data for ternary and quaternary mixtures containing soybean fatty acid methyl (FAME) and ethyl (FAEE) esters, glycerol, ethanol, methanol and water, at various temperatures. The mass balance for the compositions obtained for each phase was carried out so as to demonstrate the reliability of the models generated by the multivariate calibration. Two distinct phases are observed, a glycerol-rich and the other ester-rich, while ethanol is dissolved among the phases hence reducing the partial mutual miscibility between glycerol and ester. Through (liquid + liquid) equilibrium (LLE) results, systems containing FAEE at T = 318.15 K and 303.15 K (calibration using data obtained at temperature of 318.15 K), a good agreement is verified among the values determined using conventional and NIR technique for alcoholic phase (AP) or aqueous phase (WP) and biodiesel phase (BP). Likewise in the systems containing FAME at 318.15 K, 303.15 K and 333.15 K (calibration using data obtained at temperature of 318.15 K), the LLE results were reproduced at the upper and lower temperature to the tests of the reproducibility of the models generated by the multivariate calibration.

This work reports phase equilibrium experimental data of binary and ternary systems involving carbon dioxide (CO2), 5-(2-propenyl)-1,3-benzodioxole (safrole), and ethenylbenzene (styrene). The experimental phase equilibrium data were measured using a high-pressure variable-volume view cell based on the static synthetic method in the temperature range of (303 to 343) K, at several CO2-overall compositions and pressures up to 16 MPa. For ternary system measurements, solutions of safrole and styrene with styrene mass fractions of 0.75 and 0.90 on CO2 free basis were prepared. The results showed that, in the experimental range investigated, only vapor–liquid equilibria (VLE) were detected with bubble (BP) and dew (DP) point transitions. The experimental data were satisfactorily represented by the Peng–Robinson equation of state (PR-EoS) with the classical quadratic mixing rules. The EoS interaction parameters were fitted from binary systems and then used to predict the phase behavior of the ternary system wit...

This work is focused on the determination of liquid-liquid equilibrium data for systems containing methyl and ethyl fatty acid esters, water, glycerol and ethanol at temperatures of 303.15 K and 318.15 K using a near-infrared spectroscopy technique (NIR). The NIR method used in this investigation provided quite satisfactory results when compared to conventional analytical techniques and hence can be used as an advantageous tool to quantify the compounds involved in the liquid-liquid equilibrium systems: i) without previous preparation of the samples; ii) with less waste generation; iii) at low cost; and iv) via a non-destructive technique, as sample analyses are made directly, showing good reproducibility and reliability of the data. The NIR method was effective in the use of different temperatures for calibration and validation of the systems under study. Besides, it is shown that extrapolation with the technique may be possible, making LLE predictions feasible for other conditions not used in the calibration procedure.

5-(Oxiran-2-ilmetil)-1,3-benzodioxol ou epoxi-safrol (SO) vem sendo estudado ao longo dos anos devido a suas propriedades dependentes da concentracao, como inducao a apoptose e transdiferenciacao celular. A coprecipitacao do SO com um polimero biodegradavel e biocompativel, poli(3-hidroxibutirato-co-3-hidroxivalerato) (PHBV), foi realizada utilizando a tecnica de dispersao de solucao aumentada por fluidos supercriticos (SEDS). Um planejamento fatorial 2 4–1 foi realizado para investigar os efeitos das condicoes experimentais (pressao, vazao de solucao e de antissolvente e concentracoes de PHBV e SO) na eficiencia do processo e na morfologia dos coprecipitados. Para o material obtido SO/PHBV, foram observadas formas esfericas e fibrosas, sendo as morfologias dependentes das condicoes experimentais. Os mecanismos de liberacao controlada de epoxi-safrol para os materiais esfericos foram diferentes dos materiais fibrosos. Analise termica mostrou uma diminuicao na temperatura de maxima velocidade de degradacao (T max ) em relacao ao PHBV, atribuida a presenca de SO e a morfologia da amostra. In recent years, 5-(oxiran-2-ylmethyl)-1,3-benzodioxole or safrole oxide (SO) has been widely studied due to its concentration dependent properties, such as cellular apoptosis inducing activity and cell transdifferentiation. Coprecipitation of SO with a biodegradable and biocompatible polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), were performed using solution enhanced dispersion by supercritical fluids technique (SEDS). A 2 4–1 factorial design was carried out to investigate the effect of processing parameters (pressure, solution flow, anti-solvent flow and concentrations of PHBV and SO) on the process efficiency and microparticle morphology. Both fibrous and spherical shapes were observed for coprecipitated SO/PHBV, which were dependent on the experimental-processing conditions. Controlled release mechanisms of SO to spherical materials were different from fibrous materials. Thermal analysis showed a decrease in the temperature of maximum weight loss rate (T max ) of PHBV, attributed to the presence of SO and sample morphology.

International audience; Magnetic particles are largely used in various applications and particularly in in-vitro biomedical diagnostic and bionanotechnology. In fact, they have been employed for extraction of various biomolecules even from crude samples and as solid support in numerous samples' preparation for in-vitro diagnosis. Nowadays, they are also successfully being exploited as a carrier of biomolecules in microsystems, microfluidics, lab-on-a-chip and for detection in specific biosensors. Before any use or any preparation of magnetic hybrid particles, various factors should be considered in order to perfectly target the suitable applications. For instance, in case of nucleic acid, the particles shouldn't induce any inhibition of biological amplification techniques. For microfluidic, these particles should be colloidal stable in order to avoid any jump in the microfluidic canals. Regarding biosensor, these particles need to be chemically well designed generally to enhance specific detection or specific signal.

International audience; Magnetic particles are of great interest in various biomedical applications, such as, sample preparation, in vitro biomedical diagnosis, and both in vivo diagnosis and therapy. For in vitro applications and especially in labs-on-a-chip, microfluidics, microsystems, or biosensors, the needed magnetic dispersion should answer various criteria, for instance, submicron size in order to avoid a rapid sedimentation rate, fast separations under an applied magnetic field, and appreciable colloidal stability (stable dispersion under shearing process). Then, the aim of this work was to prepare highly magnetic particles with a magnetic core and conducting polymer shell particles in order to be used not only as a carrier, but also for the in vitro detection step. The prepared magnetic seed dispersions were functionalized using pyrrole and pyrrole-2-carboxylic acid. The obtained core–shell particles were characterized in terms of particle size, size distribution, magnetization properties, FTIR analysis, surface morphology, chemical composition, and finally, the conducting property of those particles were evaluated by cyclic voltammetry. The obtained functional submicron highly magnetic particles are found to be conducting material bearing function carboxylic group on the surface. These promising conducting magnetic particles can be used for both transport and lab-on-a-chip detection.

High pressure phase behavior experimental data have been measured for the systems carbon dioxide (CO2) + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6]) and carbon dioxide (CO2) + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6]) + 1-amino-2-phenoxy-4-hydroxyanthraquinone (C.I. Disperse Red 60). Measurements were performed in the pressure up to 18 MPa and at the temperature (323 to 353 K). As reported in the literature, at higher concentrations of carbon dioxide the phase transition pressure increased very steeply. The experimental data for the binary and ternary systems were correlated with good agreement using the Peng-Robinson equation of state. The amount of water in phase behavior of the systems was evaluated.

Magnetite-nanostructured amylose (AMY) microspheres with well-defined outlines were developed through an ultrasound-induced hydroalcoholic emulsion in 30 s. The formation of sphere-shaped polysaccharide particles occurred, upon ultrasound, via a complexation of iron ions from magnetite with carboxyl groups from carboxylated AMY at the interior of the benzyl alcohol-confined water droplets, within which the polysaccharide chains would have been fine-tuned. The introduction of magnetite into the microspheres under ultrasonic irradiation produced sub-1.78 μm size spheres and also rendered a narrower sphere size distribution. Spherical crystalline structures of magnetite with diameters ranging from 28 nm to 140 nm were observed in the AMY microspheres, indicating an excellent dispersion of the iron oxides if compared to its initial diameter (

Modification of polymers using supercritical carbon dioxide (scCO2) impregnation technology is an advantageous method for imparting desirable properties into a new polymer formulation without the architecture of the material being affected. Methyl methacrylate (MMA) and acrylic complex of europium [Eu(TTA)3AA] were impregnated on polycarbonate (PC) in the scCO2 phase. There was an increase in the amount of grafted Eu(TTA)3AA complex up to 6 h of impregnation, reaching 0.24% of grafting. For longer times of grafting, it was observed a small decrease in the amount of Eu(TTA)3AA complex in the PC polymer. On the other hand, the total amount of grafted MMA/Eu(TTA)3AA monomers increased for up to 10 h of impregnation. The PC-g-MMA/Eu(TTA)3AA copolymers showed appreciable luminescence emission at room temperature. Furthermore, the SEM images show that there was no formation of agglomerates in the structure of the copolymers over the grafting process, suggesting a excellent distribution of Eu(TTA)3AA complex in the copolymer matrix.

Activated carbons (ACs) of coconut shell produced by NaOH activation at impregnation ratios of NaOH:char (w/w) equal to 1:1 (AC-1), 2:1 (AC-2) and 3:1 (AC-3) were prepared. The properties of these carbons, including BET surface area, pore volume, pore size distribution, and pore diameter, were characterized from N2 adsorption isotherms. It was found that the ACs are essentially microporous and that the BET surface area was in order of 783 m2 g−1 for AC-1, 1842 m2 g−1 for AC-2, and 2825 m2 g−1 for AC-3. Scanning electron microscopy images showed a high pore development while Boehm method and Fourier-transform infrared spectroscopy spectra indicated the presence of acid functional groups which was confirmed by pH drift method. The adsorption equilibrium and kinetics of methylene blue (MB) onto AC-3 were carried out. Experimental data were fitted to the four isotherm models (Langmuir, Freundlich, Toth and Redlich–Peterson), and was found that Langmuir model presented the best fit, showing maximum monolayer adsorption capacity of 916 mg g−1. The kinetic studies showed that experimental data follow pseudo-second-order model. The mechanism of the adsorption process was described from the intraparticle diffusion model. The AC-3 has a high surface area and showed to be an efficient adsorbent for removal of MB from aqueous solutions.

Solid-state radical grafting of glycidyl methacrylate (GMA) onto poly(4-methyl-1-pentene) (PMP) was performed using supercritical carbon dioxide (scCO(2)) impregnation technology. The polymer films were firstly impregnated in the scCO(2) phase with the GMA using benzoyl peroxide as thermal initiator. The grafting degree and surface morphology of the samples may be controlled by the following factors: time, temperature, and pressure of impregnation. A 2(3) factorial design to evaluate the main and interaction effects of such factors on the grafting of the PMP by GMA (grafting response) was elaborated from FTIR data. The superior and inferior limits of the levels were defined on basis of a P-x-y diagram for binary system CO(2)+GMA that provided the location of the transition curves of such a system. Better grafting response was obtained for pressure of 130 bar, temperature of 70°C and time of 7h. The PMP-g-GMA films exhibited a thermal profile similar to that of the unmodified polymer. Adhesion characteristics of polymer films are dependent on grafting degree of GMA.

A zinc oxide (ZnO) and poly(ethylene terephthalate) (PET) composite was obtained using a supercritical fluid deposition (SCFD) approach. The zinc precursor was solubilized in supercritical carbon dioxide (scCO2) and impregnated onto PET films. The PET film impregnated zinc precursor was chemically treated using a hydrazine alcoholic solution to obtain the ZnO/PET composite. The composite was characterized by photoacoustic spectroscopy UV–Vis, photoluminescence emission at room temperature, and scanning electron microscopy. The ZnO generated using hydrazine presented spherical shape with strong photoluminescence emission at 390 nm (3.17 eV), indicating the formation of a well-organized ZnO phase.

The adsorption of methylene blue (MB) onto activated carbon produced from flamboyant pods ( Delonix regia ) and obtained under optimized conditions (AC op ) was carried out in this work. The experimental equilibrium data were analyzed using the isotherms of Langmuir, Freundlich, Jovanovic, Harkins–Jura, Tempkin, Redlich–Peterson, Toth, Radke–Prausnitz, Sips, Vieth–Sladek, and Brouers–Sotolongo. The adsorption kinetics of pseudo-first order, pseudo-second order, and Avrami were used for the kinetic studies. For the Toth isotherm, the value of maximum adsorption capacity ( Q m = 889.58 mg g −1 ) was close to the experimental value ( Q m = 890 mg g −1 ), and the correlation coefficient ( R 2 ) was 0.9836. The experimental data fitted very well to Avrami kinetic model. The Fourier-transform infrared spectroscopy spectra and the scanning electron microscopy images showed the presence of MB adsorbed onto AC op . Several possible mechanisms of interaction that can occur in the MB–AC op system are discussed. AC op is a fast and effective adsorbent for removing MB from aqueous solutions.

Modified chondroitin sulfate (p-CdS) microspheres were synthesized by way of crosslinking- copolymerization reaction with N-isopropylacrylamide (NIPAAm), yielding CdS-co-PNIPAAm copolymer net- work. The incorporation of vinyl groups onto the CdS was processed with the use of glycidyl methacrylate (GMA) in an aqueous solution of pH 3.5 under stirring speed of 800 rpm at 50 � C. 13 C NMR and 1 H NMR spectra of CdS treated with the GMA indicated the formation of 3-metha- cryloyl-1-glyceryl ester of p-CdS and 3-methacryloyl-2- glyceryl ester of p-CdS that are the reaction products resultant of an epoxide ring-opening mechanism via. The synthesis of microspheres was performed via radical reac- tion of the vinyl groups at the p-CdS with vinyl groups at the NIPAAm in a waterbenzyl alcohol microemulsion. The formation of spherical structures is the result of the polymerization-crosslinking reaction of the p-CdS with the NIPAAm monomers at the droplets of water, in view that both reactants have hydrophilic characteristics at the tem- perature at which the reaction was processed. The pure CdS hydrogel microspheres showed a slightly cracked structure with a lower diameter range while the CdS-co- PNIPAAm hydrogel microspheres showed a flat and tight structure with a more regular mass distribution. V C 2011

This work describes the preparation of composite films of zinc oxide (ZnO) embedded in a covalent copolymer substrate of triethylene glycol dimethacrylate and poly(ethyleneglycol) diacrylate. The ZnO-embedded copolymer was produced in situ from the reaction of a doped precursor zinc bis(2-thenoyltrifluoroacetonate) [Zn(TTA)2] in a hydrazine hydrate reflux system. The in situ production of ZnO nanoparticles with excellent optical qualities embedded in the copolymer substrate was demonstrated to be an effective approach to fabricating new advanced materials for use as a protective barrier that blocks UV rays.

Smart hollow microspheres composed of vinyled-chondroitin sulfate conjugates (CSπ) and magnetite nanoparticles were obtained by the intermediate of a multiple emulsion in absence of a surfactant, attributable to stabilizing properties of the CS. It was formed an oil–water multiple emulsion in which the CS played a role as an anionic stabilizer for magnetite nanoparticles via complexation. Iron oxides were bonded to the microspheres by the formation of a complex of Fe 3+ ions on the crystalline phase with oxygen atoms at the carboxyl groups without their magnetic properties being affected. The average crystal size of embedded magnetite nanoparticles was approximately 16.5 nm, indicative of a good dispersion in microspheres. Furthermore, the introduction of iron oxides resulted in microspheres with a higher diameter and a narrower particle size distribution.

Nanocomposite hydrogel consisting of dispersed montmorillonite-crosslinked maltodextrin-co-dimethylacrylamide (malt-dex-co-DMAAm) as a highly stable device was developed. Carbon–carbon π-bonds issued from glycidyl methacrylate (GMA) were incorporated onto both the MMT (MMT-π) and the malt-dex (malt-dex-π) structures. The nanocomposite copolymer hydrogel was processed via radical crosslinking reaction of malt-dex-π with MMT-π in the presence of DMAAm. The radical reaction of the carbon–carbon π-bonds at the MMT-π was verified by treating the MMT-π with sodium persulfate. There was an excellent dispersion of the MMT-π at the interior of the matrix even after the nanocomposite hydrogel being swollen, demonstrating that the developed methodology can imprint stability of mineral nanoparticles into a porous polymer network preventing diffusion of water-bonded silicate platelets toward the outside matrix. The water absorption profile became more dependent on the polymer relaxation for mineral-loader nanocomposite hydrogels. Higher water absorption had an impact on reduction of elasticity modulus due to softer polymer network in swollen state.

The objective of this work was to investigate the application of the solution enhanced dispersion by supercritical fluids (SEDS) technique for the precipitation of pure β-carotene and copolymer poly(3-hydroxybutirate- co -hydroxyvalerate) (PHBV), as well as some encapsulation tests of the solute in the biopolymer. The following parameters were investigated in the precipitation of pure β-carotene: pressure (8.0 and 12.0 MPa), anti-solvent flow rate (20–40 mL/min) and concentration of β-carotene in an organic dichloromethane solution (4 and 8 mg/mL). For pure β-carotene, the results showed that the mean particle size varied from 3.8 to 246.8 μm, depending on the processing conditions. The morphology of β-carotene was modified from plate-like to leaf-like particles, as verified by micrographs of scanning electronic microscopy (SEM). For the PHBV precipitation, the SEM micrographs showed that for all experimental conditions the morphology of polymer was different from the unprocessed material. The precipitated polymer presented a quasi-spherical shape with interconnected particles in the sub-micrometric range (particle size in the range of 278–570 nm), while the unprocessed material was composed of films and large blocks. The co-precipitation tests showed that the best ratio of β-carotene to PHBV in solution was 1:3 (w/w), which resulted in approximately 80% of encapsulation. Fluid phase behavior of the ternary systems CO 2 + dichloromethane + β-carotene and CO 2 + dichloromethane + PHBV was also investigated with the aim of elucidating the region of the phase diagram in which the precipitation occurs. Phase equilibrium data were measured in the temperature range of 303–343 K, with CO 2 compositions ranging from 40 to 90 wt% for β-carotene, and from 30 to 90 wt% for PHBV. Vapor–liquid and also solid–vapor–liquid phase transitions were observed in the phase equilibrium study. It was observed that the presence of β-carotene or PHBV in the ternary mixture had a little influence on the fluid phase behavior of the systems.

Microparticles of theophylline were recrystallized using the high-pressure antisolvent technique. A mixture of ethanol and dichloromethane with a volumetric ratio of 1:1 was used as solvents, and compressed CO 2 as antisolvent. The effects of process parameters (temperature, flow rate of solution and antisolvent, drying rate, initial solution concentration, diameter and length of the capillary expansion tube, and pressure gradient between the organic solution feed and the precipitation chamber) on particle size, size distribution and morphology were evaluated through an experimental design technique. In order to help selecting the appropriate operating conditions and understand the precipitation mechanism, the fluid phase behavior of ternary (CO 2 -solvents) and quaternary (CO 2 -solvents–theophylline) systems were investigated using a static synthetic method. Plate-like particles were produced in all experimental conditions with length ranging from 3 to 70 μm. Also, slightly agglomerated particles were produced in some experiments, while in others a quite pronounced agglomeration was observed. Phase diagram of the mixture revealed that the contact mechanism between solution and antisolvent occurred in two different ways, influencing the aggregation, particle size and particle size distribution. The X-ray powder diffraction patterns (XRD) showed a change in theophylline crystallinity. This fact was confirmed by differential scanning calorimetry (DSC) analysis. Also, infrared spectroscopy analysis (FTIR) showed that the recrystallized powder presented a degree of purity higher than that of unprocessed theophylline. Thermal gravimetric analysis (TGA) indicated that the lower mass loss temperature values were found for small size particles and particles with crystalline structure.

This work reports the synthesis of particles based on poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV) polymer that were impregnated with progesterone. The PHBV particles were obtained by supercritical CO2 (scCO2) anti-solvent expansion (SAS). scCO2 was also used at a high pressure (25 MPa) and moderate temperature (323 K) for the impregnation of progesterone into the PHBV particles at different impregnation times. In vitro release tests showed that the half-time of progesterone release in a hydro-alcoholic medium, for the samples produced with impregnation times of 2–32 h, was 3–5 h, with the higher release times generally related to smaller impregnation times.

This work investigates the influence of temperature, pressure, exposure times and depressurization rate on the activity of two commercial immobilized lipases submitted to compressed carbon dioxide, propane and n -butane. A high-pressure cell was employed in the experiments, varying the temperature from 35 to 75 °C, in the pressure range of 10–280 bar, exposure times from 1 to 6 h and adopting distinct decompression rates. Results showed that activity losses were verified for Lipozyme IM in all compressed solvents, markedly in carbon dioxide. For Novozym 435, treatment in carbon dioxide though in less extent also led to activity losses, while the use of propane and n -butane promoted enhancements of the enzyme activity. In general, within the range studied, temperature and exposure times affected positively enzyme activity while the decompression rates did not demonstrate to be a relevant variable. Additionally, an exploratory study was conducted to investigate the effect of compression/expansion cycles on enzyme activity in all solvents. Thermogravimetric analyses show that the thermal profiles of Novozym 435 treated in n -butane and in carbon dioxide are similar to the untreated enzyme. Scanning electron micrographs of Novozym 435 illustrate that the material submitted to carbon dioxide presented morphological alterations when compared to the untreated enzyme.

This work reports experimental phase equilibrium data of binary and ternary systems involving carbon dioxide, propane, and glycidyl methacrylate (GMA). Phase equilibrium experimental data were obtained according to the static synthetic method using a variable volume view cell. The experiments covered the temperature range of (303 to 343) K, pressures up to 13 MPa, at several overall compositions. The experimental data were modeled with the Peng−Robinson equation of state (PR-EoS) with the conventional quadratic mixing rules. The EoS interaction parameters were fitted from binary systems and then used to predict the phase behavior of the ternary system. The results showed that, in the experimental range investigated, only vapor−liquid transitions were found and that the PR-EoS was capable of satisfactorily representing the experimental data.

Electrically conductive films were obtained by solid phase photopolymerization of pyrrole (Py) into a poly(vinylchloride) (PVC) matrix. We attempted to characterize the structure, electrochemical and thermal properties, and morphology of the resulting polypyrrole/PVC blend. The blend obtained has low conductivity and rather poor electroactivity due to the loss of conjugation length of polypyrrole (PPy) provoked by halogenation. Micrographs of cryofracture surface suggested two distinct phases, and thermogravimetric analysis revealed a low thermal stability of the blend. On the basis of our experimental results, we propose a reaction mechanism that explains the PPy formation in solid phase induced by UV light.

Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films has been studied using supercritical carbon dioxide (SC-CO 2 ) as a solvent and a swelling agent. As the reaction temperature was below the melting point, PP was modified in the solid phase. The PP film was first soaked with the monomer GMA and benzoyl peroxide (BPO) as an initiator using SC-CO 2 at different experimental conditions of pressure, temperature, and thermal treatment time. After releasing CO 2 , film GMA molecules were grafted onto PP in different times. Using this method, the degree of grafting and the morphology could be controlled through the combination of pressure, temperature, and soaking time. FTIR spectra confirmed that GMA had been grafted onto PP and that polypropylene-graft-glycidyl methacrylate (PP-g-GMA) presented a high surface reactivity for conductive polyaniline anchoring. DSC measurements and TG analyses showed that the thermal profiles of the graft copolymer and virgin PP are quite similar and that the graft PP does not exhibit changes in terms of thermal degradation profile and melting temperature, respectively. X-ray data showed that a high degree of grafting leads to a lower degree of crystallinity of polypropylene.

Silica as a reinforcement filler for automotive tires is used to reduce the friction between precured treads and roads. This results in lower fuel consumption and reduced emissions of pollutant gases. In this work, the existing physical interactions between the filler and elastomer were analyzed through the extraction of the sol phase of styrene-butadiene rubber (SBR)-butadiene rubber (BR)/SiO 2 composites. The extraction of the sol phase from samples filled with carbon black was also studied. The activation energy (E a ) was calculated from differential thermogravimetry curves obtained during pyrolysis analysis. For the SBR-BR blend, E a was 315 kJ/mol. The values obtained for the composites containing 20 and 30 parts of silica per hundred parts of rubber were 231 and 197 kJ/mol, respectively. These results indicated an increasing filler-filler interaction, instead of filler-polymer interactions, with respect to the more charged composite. A microscopic analysis with energy-dispersive spectroscopy showed silica agglomerates and matched the decreasing E a values for the SBR-BR/30SiO 2 composite well.

The modification of polyethylene surface has been used to obtain better interaction between organic polymeric surfaces and inorganic species. A previous treatment with modifiers is required in order to provide the adherence to the polymer surface. Our objective was the synthesis and the electrical characterization of copper sulfide coated low-density polyethylene (CuS-LDPE) films. SEM micrographs and AFM images showed a homogeneous distribution of copper sulfide, which contributes to the increasing of the electrical conductivity. X-ray analysis showed an increase of the copper sulfide crystals according to the number of immersions in the precursor sulfide solution. The measured conductivity of the CuS-LDPE films was in the range of 3.6–163.3 S cm −1 , according to the number of immersions on the precursor solution.

Surface modification of polyimides has been used to obtain better interaction with an inorganic material. Copper sulfide incorporation onto the surface of commercial Kapton® polyimide showed that treatment with base was necessary for adherence of the copper sulfide to the polymeric matrix. The optimized conditions for composite preparation, obtained by response surface methodology, was pH 1.4 at 80 °C for 3.67 h. Using these conditions, we obtained electrical resistance as low as 1.0 ohm for CuS\Kapton® composites. These optimized conditions were used to prepare other low-resistance polyimide composites. The resulting composites were analyzed by photoelectron spectroscopy. The presence of S(2p) and Cu(2p) peaks demonstrated the incorporation of copper sulfide onto the polyimide surface. Scanning electron microphotographs and the images from atomic force microscopy showed a homogeneous CuS distribution in all composites.

Supported and stable inorganic crystals in nanometric size, such as PbS or other quantum dots, are very desired materials in the form of thin films for the application in technological areas. Herein, an approach to the growth of PbS crystals in poly(acrylic acid) (PAA) ultrathin film covalently immobilized in the polyethylene (PE) surface is described. The method used allows the obtaining of materials with different shapes and sizes by the adjustment of experimental variables. The more homogenous composites with the smallest particles were obtained at pH 6 due to the slower removal of Pb2+ ions from PAA ultrathin film. Hence, the PbS is formed in situ inside of PAA. A direct relationship between Pb2+ and thioacetamide (TAA) concentrations was observed by the analysis of the composite morphologies. More homogenous composites with the smallest particles were obtained in the lowest Pb2+ condition and the highest TAA concentration condition or in the intermediate Pb2+ condition and the lowest TAA concentration condition. Nanocristais inorgânicos estáveis e suportados, como PbS ou outros quantum dots, são materiais extremamente importantes quando obtidos na forma de filmes finos para a aplicação em áreas tecnológicas. Neste trabalho, um método para o crescimento de cristais de PbS sobre filme ultrafino de poli(ácido acrílico) (PAA) covalentemente imobilizado na superfície de polietileno (PE) é descrito. O método utilizado permite a obtenção de materiais com diferentes formas e tamanhos pelo ajuste de variáveis experimentais. Os compostos mais homogêneos e com as menores partículas foram obtidos em pH 6 devido a remoção mais lenta de íons Pb2+ adsorvidos no filme ultrafino de PAA. Dessa forma, o PbS é formado in situ no interior do PAA. A análise da morfologia dos compósitos mostrou uma relação direta entre a concentração de Pb2+ e a concentração de tioacetamida (TAA). Compósitos mais homogêneos com as partículas menores foram obtidos na condição de menor concentração de Pb2+ e maior concentração de TAA ou na condição intermediária de Pb2+ e menor concentração de TAA.

Supercritical CO2 has been used to prepare silver polymer composites, silver/poly(vinyl alcohol) and silver/poly(vinyl alcohol)/sulfonated poly(ethylene terephthalate) through impregnation of a silver precursor in solid-state polymeric matrices followed by thermal reduction of the silver precursor. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, thermogravimetric analysis and UV/vis spectroscopy indicate that synthesis conditions and polymeric matrix composition affect silver particle size, shape and distribution in polymeric matrices. Silver particles are smaller, have a more uniform shape and present narrower size distribution in PVA-rich than in PETs-rich composites. CO2 supercrítico foi utilizado para preparar compósitos poliméricos com prata, prata/poli álcool vinílico e prata/ poli álcool vinílico/ poli (tereftalato de etileno) sulfonado, pela impregnação de um precursor de prata nas matrizes poliméricas no estado sólido seguida da redução térmica do precursor. Difração de raio X, microscopia eletrônica de varredura, espectroscopia de energia dispersiva, microscopia de força atômica, análise termogravimétrica e espectroscopia no UV/vis dos compósitos indicaram que as condições de preparação e a composição da matriz polimérica influenciam o tamanho e a forma das partículas de prata formadas, assim como, a uniformidade e a distribuição das partículas nas matrizes poliméricas. As partículas de prata nos compósitos ricos em PVA são menores, possuem formas mais uniformes e apresentam distribuição de tamanho mais estreita do que nos compósitos ricos em PETs.

Polymers of great commercial use such as polyethylene, polypropylene and polystyrene have had their surface properties modified. Many researchers have recently altered the properties of polymers via grafting reactions. In this work, the surface of low-density polyethylene (LDPE) submitted to grafting with maleic anhydride followed by hydrolysis, chlorination, amination and protonation reactions was analyzed by atomic force microscopy, scanning electric potential microscopy, Fourier transform IR spectroscopy and water contact angle measurements. In different micrographs of the LDPE surface modified by four different processes it was possible to observe that the mountain-shaped structures with a global peak in the virgin polyethylene had become peaky in the grafting steps. It was possible to see that the LDPE surface becomes less rough with the hydrolysis process, going back to values close to those for the virgin polyethylene in the following steps. In scanning electric potential microscopy and topographic micrographs of a chlorinated sample it was possible to observe a correlation between the extent of surface modification and surface topography.

This work reports experimental data of polycaprolactone (PCL) polymer solubility in chloroform as solvent and n-hexane, methanol, ethanol and isopropanol as nonsolvents, at atmospheric pressure (about 1,0 bar) and temperature of 303.15 K. It was used PCL with 70000-90000 and 2000 molar mass (MM). The experiments of solubility were performed using a jacketed-cell with temperature controlled by an ultrathermostatic bath, in which a turbidity method was adopted and used. From the obtained results it should be observed that the n-hexane presented a more pronounced anti-solvent effect in the PCL solubility, where the heterogeneous region (solid phase presence) was broader than when other nonsolvent. It was also observed that the binodal curves measured with the high molar mass polymer showed similar results compared to the low molar mass one.

Brain-resembling superabsorbent hydrogel composites were developed via UV-induced copolymerization-crosslinking of vinyl-modified starch with acrylic acid (AAc) and N,N-dimethylacrylamide (DMAAm) in the presence of Fe3O4 particles. The iodine test revealed the actual 3D network structure of starch within the swollen hydrogel composite. FTIR spectra of the hydrogel composites indicated interaction between the carboxyl groups from a hydrogel and the iron ions from Fe3O4. The formation of the hydrogel composites also was evidenced by wide-angle X-ray diffraction (WAXD) and energy dispersive X-ray (EDS) spectroscopies. Scanning electron microscopy (SEM) images revealed a homogeneous material since no phase separation between the hydrogel and the Fe3O4 phases could be observed. Minimal fragments of the swollen composite allowed the study of its actual morphology by TEM imaging. Stick-type structures were observed in the composite, as a result of a water-equilibrated structural configuration (obtained in a swollen state) of carboxyl groups of AAc coordinated to iron ions of Fe3O4. The albumin release mechanism of the hydrogel without Fe3O4 is governed by macromolecular relaxation. In the hydrogel composites, the albumin release was driven by macromolecular relaxation, but with a strong tendency to anomalous transport, because of both the tortuosity effect and attenuation of the anion–anion electrostatic repulsion forces. On the other hand, the albumin release became more dependent on anomalous transport with an applied magnetic field, which intensified the tortuosity effect. The proposed hydrogels are more appropriate for use as oral drug delivery systems because they provide a better sustention of the drug over the in vitro release experiment.

Covalent TiO 2 -co-pectin microspheres containing Fe 3 O 4 nanoparticles were developed through an ultrasound-induced crosslinking/polymerization reaction between the glycidyl methacrylate from vinyl groups in TiO 2 and in pectin. ζ -potentials became less negative in the nanostructured microspheres, caused by the presence of both inorganic particles in the negatively charged pectin. The nanostructured pectin microspheres showed an amoxicillin release rate slower than that of pure pectin microspheres. The proposed microspheres were found to be a sustained release system of amoxicillin in the acid medium. Furthermore, the antibiotic release may be modulated by exposition of the microspheres to a remote magnetic field. In practical terms, the nanostructured microspheres could deliver a larger proportion of their initial load to specific site of action. The cytotoxic concentrations for 50% of VERO cells (CC 50 ), calculated as the concentration required to reduce cell viability by 50% after 72 h of incubation, for pectin-only microspheres and nanostructured pectin microspheres were 217.7 ± 6.5 and 121.5 ± 4.9 μg mL −1 , respectively. The obtained CC 50 values indicated acceptable cytotoxic levels for an incubation period of 72 h, showing that the pectin microspheres have a great pharmacological potential for uses in biological environments, even after the introduction of both Fe 3 O 4 and TiO 2 .

Films of polypropylene (PP) were grafted with glycidil methacrylate (GMA) using supercritical CO2 as swelling agent and solvent. Different pressures and temperatures were used to study their effects on the soaking and grafting process. FTIR results showed signals at 1726 and 1640 cm-1, assigned to C=O and C=C (after the soaking process), and a decreased signal at 1640 cm-1 (after the grafting procedure), suggesting the effective grafting of GMA. For the grafted material immersed in ethylenediamine, peaks in the 3600 to 3250 cm-1 range (N-H stretching) were evident. Contact angle measurements showed an increasingly hydrophilic nature in the direction from pure PP to grafted PP/GMA (PP-g-GMA) to PP-g-GMA immersed in ethylenediamine (PP-g-GMA/En). X-ray photoelectron spectroscopy provided evidenced of the effective incorporation of ethylenediamine in the grafted material.