Search

Conventional and commercially available DNA extraction methods have several limitations regarding, for instance, contamination, and complex and slow precipitation and recovery processes. Herein, we report the synthesis of oxygen and phosphorus-doped Graphitic carbon nitride structures (g-POCN), via a novel Zinc-catalyzed one-pot solvothermal approach, and its application in the extraction of genomic DNA (gDNA) from a vegetal matrix (P. argentatum). Experimental and molecular modeling analyses demonstrate the high affinity of gDNA with g-POCN, which provided highly efficient gDNA extraction processes, with extraction yield, as well as integrity and quality of the extracted gDNA, comparable or superior to a commercial extraction kit and isopropanol extraction. Moreover, under suitable elution conditions, this method allows the easy removal of high concentrations of gDNA from g-POCN, rendering this method as a low-cost, simple, and fast approach for the extraction of even small amounts of gDNA. Remarkably, the extracted gDNA shows no degradation, and no inhibition of the polymerase chain reaction. Therefore, g-POCN represents a promising material for the highly efficient, cost-effective, and biocompatible extraction of DNA, which could stimulate research focused on broad DNA sources, e.g., RNA extraction, plasmids, ssDNA, etc.

The present investigation involves the coordinative chain transfer polymerization (CCTP) of biobased terpenes in order to obtain sustainable polymers from myrcene (My) and farnesene (Fa), using the ternary Ziegler–Natta catalyst system comprising [NdV3]/[Al(i-Bu)2H]/[Me2SiCl2] and Al(i-Bu)2H, which acts as cocatalyst and chain transfer agent (CTA). The polymers were produced with a yield above 85% according to the monomeric consumption at the end of the reaction, and the kinetic examination revealed that the catalyst system proceeded with a reversible chain transfer mechanism in the presence of 15–30 equiv. of CTA. The resulting polyterpenes showed narrow molecular weight distributions (Mw/Mn = 1.4–2.5) and a high percent of 1,4-cis microstructure in the presence of 1 equiv. of Me2SiCl2, having control of the molecular weight distribution in Ziegler–Natta catalytic systems that maintain a high generation of 1,4-cis microstructure.

In this work, the bolometric parameters of Sierpinski fractal antenna-coupled SWCNT semi-metallic films are obtained by thermoelectric characterization, this in order to find out the performance as bolometer. The method was based on an experimental setup considering a line-of-sight wireless link between two identical planar fractal antennas, infrared thermography, and electrical resistance measurements. The experimental setup considered the antennas resonant frequencies. Both the transmitting and receiving antenna were third-iteration Sierpinski fractal dipoles designed to work at UHF frequencies. Films made either of cracked or uncracked SWCNT films were each separately coupled to the receiving fractal antenna. Measurements showed that the receiving antenna that was impinged with radiation at UHF frequencies coming from the transmitting antenna, experienced as it was expected an induction of electric current, the induced current flowed through the film producing a temperature change, which in turn caused changes in the radiated heat of the film, as well as changes in the electrical resistance known as Temperature Coefficient of Resistance TCR. The maximum value of TCR for uncracked SWCNT films was −3.6%K−1, higher than the one observed for cracked SWCNT films which exhibited a maximum value of −1.46%K−1. Measurements for conversion of incident radiation to electrical signals known as the Voltage Responsivity ℜv, exhibited values of 9.4 mV/W and 1.4 mV/W for uncracked SWCNT films and cracked SWCNT films, respectively.

Considering the current trend of finding sustainable alternatives to the existing fossil-based plastics, in this review we describe what makes a bioelastomer “bio” and what this implies in terms of materials design. We analyze the current state of development of bioelastomers, including the most important types, their current and upcoming use, and their synthetic pathways. Moreover, we provide a general landscape of the hybridization or composite preparation of elastomers to acquire specific functionalities and their implementation in advanced applications, focusing mainly on electronics and biomedicine. Furthermore, we show how through the use of bioelastomers, one can, besides helping the environment, achieve materials with exceptional performances (e.g., very high mechanical properties and/or self-healing properties), which can be processed via novel techniques such as 3/4D-(bio)printing.

En este trabajo reportamos el desarrollo de un control de obturadores para un sistema de crecimiento por Haces Moleculares (EHM) o del Ingles Molecular Beam Expitaxy (MBE) utilizando una interfaz gráfica de LabView y la plataforma de Arduino Mega para la adquisición de datos. La técnica de epitaxia por haces moleculares permite controlar espesores a escala nanométrica de muy alta calidad cristalina, para la fabricación de dispositivos electrónicos y optoelectrónicos.

Se presenta una propuesta metodológica para el análisis de resultados de gráficos estadísticos, en donde el ancho de bin es el principal factor de cambio para su representación. Se implementa un pseudocódigo que permite visualizar los pasos a seguir para obtenerlo. Se realizó un ejercicio para mostrar la pérdida o ganancia de información al implementar la Densidad de Kernel y también la ausencia de esta. La propuesta se hizo directamente con la metodología de Bowman y Azzalini (1997) en Matlab y el generado en este trabajo. Se utilizó el test de Kolmogorov-Smirnov para validar las ventajas del método propuesto. Se encontró que el método propuesto permite una mejor tendencia de los datos ya sea positiva, negativa o simétrica y poca o escasa pérdida de información con respecto evaluación estadística aplicando densidad de kernel; de este modo es una opción para obtener un mejor análisis estadístico cuantitativa y cualitativamente y además puede ser reproducido en temas similares.

The growing concern for environmental problems has motivated the use of materials obtained from bio-based resources such as cellulose nanocrystals which have a promising application acting as fillers or reinforcements of polymeric materials. In this context, in this article, plasma-induced polymerization is proposed as a strategy to modify nanocrystals at different plasma power intensities using ε-caprolactone and δ-decalactone to improve their compatibility with polymeric matrices. The characterization was carried out using techniques such as FTIR, TGA, XRD, XPS, and AFM, with which a successful functionalization was demonstrated without altering the inherent properties of the nanocrystals. The preparation of ABS nanocomposites was carried out with the modified nanoparticles and the evaluation of the mechanical properties indicates an increase in Young’s modulus and yield stress under certain concentrations of modified cellulose nanocrystals.

Polyaniline (PANI) composites have gained momentum as supercapacitive materials due to their high energy density and power density. However, some drawbacks in their performance remain, such as the low stability after hundreds of charge-discharge cycles and limitations in the synthesis scalability. Herein, we report for the first time PANI-Graphitic oxidized carbon nitride composites as potential supercapacitor material. The biomimetic polymerization of aniline assisted by hematin, supported by phosphorous and oxygen-modified carbon nitrides (g-POCN and g-OCN, respectively), achieved up to 89% yield. The obtained PAI/g-POCN and PANI/g-OCN show enhanced electrochemical properties, such as conductivity of up to 0.0375 S/cm, specific capacitances (Cs) of up to 294 F/g (at high current densities, 5 A/g) and a stable operation after 500 charge-discharge cycles (at 3 A/g). In contrast, the biomimetic synthesis of Free PANI, assisted by stabilized hematin in cosolvents, exhibited lower performance properties (65%). Due to their structural differences, the electrochemical properties of Free PANI (conductivity of 0.0045 S/cm and Cs of up to 82 F/g at 5 A/g) were lower than those of nanostructured PANI/g-POCN and g-OCN supports, which provide stability and improve the properties of biomimetically synthesized PANI. This work reveals the biomimetic synthesis of PANI, assisted by hematin supported by modified carbon nitrides, as a promising strategy to produce nanostructured supercapacitors with high performance.

Xyleborus sp beetles are types of ambrosia beetles invasive to the United States and recently also to Mexico. The beetle can carry a fungus responsible for the Laurel Wilt, a vascular lethal disease that can host over 300 tree species, including redbay and avocado. This problem has a great economic and environmental impact. Indeed, synthetic chemists have recently attempted to develop new neonicotinoids. This is also due to severe drug resistance to “classic” insecticides. In this research, a series of neonicotinoids analogs were synthesized, characterized, and evaluated against Xyleborus sp. Most of the target compounds showed good to excellent insecticidal activity. Generally, the cyclic compounds also showed better activity in comparison with open-chain compounds. Compounds R-13, 23, S-29, and 43 showed a mortality percent of up to 73% after 12 h of exposure. These results highlight the enantioenriched compounds with absolute R configuration. The docking results correlated with experimental data which showed both cation-π interactions in relation to the aromatic ring and hydrogen bonds between the search cavity 3C79 and the novel molecules. The results suggest that these sorts of interactions are responsible for high insecticidal activity.

En este trabajo se presentan estudios de composición química y de control de crecimiento de pozos cuánticos semiconductores basados en semiconductores III-V (AlGaAs/GaAs/AlGaAs, utilizando una composición del Al de 33 %) y fabricados en un sistema de epitaxia por haces moleculares. Se utilizó la técnica de difracción de electrones reflejados de alta energía (in-situ) para la caracterización por composición química, así como la técnica de espectroscopía por fotoluminiscencia (ex-situ) a baja temperatura para el análisis de los niveles de energía de tres diferentes pozos cuánticos no-acoplados. Se obtuvo una buena correlación entre el monitoreo superficial y la caracterización espectroscópica de la muestra estudiada.

This article proposes a strategy to functionalize cellulose nanocrystals by means of plasma-surface modification utilizing monomers of different nature: caprolactone, styrene and farnesene. The surface characteristics of the nanocrystals were studied by different techniques including XPS, FTIR and STEM, demonstrating that this technique allows a successful functionalization, yielding homogenous functionalization which does not alter the rod-like shape of the nanocrystals, and therefore their anisotropic behavior. We have furthermore studied the employment of the modified nanocrystals as reinforcement additive of ABS, which significantly enhanced the impact resistance of the thermoplastic, which could have great implications for industrial applications.

espanolEn este trabajo se reporta la fabricacion de un dispositivo laser de semiconductores III-V de confinamiento separado. La heteroestructura se crecio usando la tecnica de epitaxia por haces moleculares y se caracterizo optica, topografica y electricamente por medio de fotoluminiscencia, microscopia de tunelamiento, electroluminiscencia, relaciones de corriente-voltaje y corriente-potencia, respectivamente. El confinamiento electronico es llevado a cabo por un emparedamiento del area activa con pozos cuanticos de InGaAs con una composicion que permite un acople estructural entre el pozo cuantico y los puntos cuanticos autoensamblados de InAs disminuyendo las dislocaciones que darian lugar a una mala calidad del dispositivo. El objetivo es obtener una emision laser en las ventanas de menor absorcion de las fibras opticas situadas en el cercano infrarrojo en las que se basan los sistemas de telecomunicacion. EnglishIn this work the fabrication of III-V semiconductor laser device with separate confinement is reported. The heterostructure was grown by molecular beam epitaxy technique and it was characterized by optical, morphological and electrical techniques such as photoluminescence, scanning tunneling effect, electroluminescence, current-voltage and current-power relations, respectively. The electronic confinement was carried out by sandwiching the active area with InGaAs quantum well with an appropriated Indium composition that allows a structural coupling between quantum wells and self-assembled InAs quantum dots decreasing dislocations that could commit the device quality. Our aim is to obtain the laser emission in the lower absorption windows for optical fiber telecommunications systems located in the near-infrared.

Se presenta el estudio de nanoantenas de geometría estelar como elementos plasmónicos amplificadores y direccionales del campo electromagnético. El estudio se llevó a cabo con análisis numérico basado en la técnica del elemento finito. Fueron analizados varios materiales, dimensiones arreglos geométricos y frecuencias para la simulación y el análisis de datos. La geometría estelar fue elegida con base en la propiedad de autoensamblado de los materiales de plata-óxido de zinc (Ag-ZnO). La direccionalidad y la amplificación del campo eléctrico fueron simulados tanto en campo cercano como en campo lejano. Adicionalmente se discuten algunas aplicaciones de estas nanoestructuras.

Forty years after the discovery of metallocene catalysts, there are still several aspects that remain unresolved, especially when the &ldquo, conventional&rdquo, alkylaluminum activators are not used. Herein, we systematically investigated the synthesis of polyethylene (PE) via three different zirconocene catalysts, with different alkyl substituents, activated via different organoboron compounds. The polymerization behavior, as well as the properties of the materials, were evaluated. The results demonstrate that the highest catalytic activity is shown by bis(cyclopentadienyl)dimethylzirconium activated by trityl tetra(pentafluorophenyl)borate. Additionally, it was found that toluene is the optimum solvent for these systems and at these reaction conditions. Moreover, to validate our experimental results, a comprehensive mathematical model was developed on the basis of thermodynamic and kinetic principles. The concentration of ethylene transferred to the solvent phase (toluene) in a liquid&ndash, vapor equilibrium (LVE) system was estimated based on Duhem&rsquo, s theorem. Arrhenius expressions for the kinetic rate constants of a proposed kinetic mechanism were estimated by a kinetic model, in which the rate of polymerization was fitted by a least-square optimization procedure and the molecular weight averages by the method of moments. The simulations of the coordination polymerization suggest the presence of two types of active sites, principally at low temperatures, and the reactivation of the deactivated sites via a boron-based activator. However, the effect of the temperature on the reactivation step was not clear, a deeper understanding via designed experiments is required.

Synthetic steroid hormones are widely used in our daily lives for contraception, in the treatment of diseases, and in the livestock industry. However, steroidal hormones are considered emerging contaminants in wastewater worldwide, due to their widespread presence and adverse effects on both aquatic organisms and humans. There are also existing compounds that alter the endocrine system, such as steroidal hormones, degradation products of nonionic surfactants such as alkylphenols, plasticizers, inorganic compounds, and pharmaceutical products. The present review opens with a general introduction of membrane separation, followed by a review on the fabrication of membranes. Continuing with these general fabrication aspects, a brief theoretical section of the basic principles of mass transport through a membrane is presented. Furthermore, some generalities about the removal of pharmaceuticals and hormones are provided, finalizing with a look toward the future of membrane separation processes.

Syntheses of biolestomers through the coordination polymerization of terpenes, such as ocimene (Oc), β-myrcene (My) andtrans-β-farnesene (Fa), using catalyst systems based on neodymium versatate (NdV3) are reported in this work. All polymerization products were characterized by size exclusion chromatography, differential scanning calorimetry and nuclear magnetic resonance in order to determine their macromolecular, thermal and structural characteristics. The NdV3in combination with diisobutylaluminum hydride as cocatalyst and diethylaluminum chloride (DEAC) as halogen source was found effective for Oc polymerizations providing polyocimenes with molecular weights (Mn) in the order of 20 to 57 Kg/mol, broad molecular weight distributions (Mw/Mn) since 3.8 until 8.2, preferablycis-1,4 content (61-69 %) and glass transition temperatures (Tg) in the range of-30 to-26 °C. On the other hand, the same NdV3but now activated by modified methylaluminoxane and DEAC was found considerably active in My and Fa polymerizations, affording polymyrcenes and polyfarnesenes withMnbetween 155 and 243 Kg/mol, as well asMw/Mnranging between 3.1-3.9 and 1,4 content values were found higher than 94 % for this subfamily of polyterpenes, being the 3,4 content the complement for completing 100 %. Moreover, it was demonstrated thatTgof polyterpenes studied depends on the size of pendant group, shifting it towards lower temperatures as increasing the size of the pendant group.

Se presenta un método para modelado geométrico aplicando un algoritmo genético en el que la población (individuos) son los puntos de control de curvas Bézier de primer, segundo o tercer grado. Con la aplicación de este método se obtienen figuras sólidas, continuas y suavizadas y se discuten algunas aplicaciones que van desde la ingeniería de nanomateriales, pasando por el modelado de prótesis hasta macro estructuras mecánicas complejas y ciencias sociales.

This article proposes a process to prepare fully bio-based elastomer nanocomposites based on polyfarnesene and cellulose nanocrystals (CNC). To improve the compatibility of cellulose with the hydrophobic matrix of polyfarnesene, the surface of CNC was modified via plasma-induced polymerization, at different powers of the plasma generator, using a trans-β-farnesene monomer in the plasma reactor. The characteristic features of plasma surface-modified CNC have been corroborated by spectroscopic (XPS) and microscopic (AFM) analyses. Moreover, the cellulose nanocrystals modified at 150 W have been selected to reinforce polyfarnesene-based nanocomposites, synthesized via an in-situ coordination polymerization using a neodymium-based catalytic system. The effect of the different loading content of nanocrystals on the polymerization behavior, as well as on the rheological aspects, was evaluated. The increase in the storage modulus with the incorporation of superficially modified nanocrystals was demonstrated by rheological measurements and these materials exhibited better properties than those containing pristine cellulose nanocrystals. Moreover, we elucidate that the viscoelastic moduli of the elastomer nanocomposites are aligned with power–law model systems with characteristic relaxation time scales similar to commercial nanocomposites, also implying tunable mechanical properties. In this foreground, our findings have important implications in the development of fully bio-based nanocomposites in close competition with the commercial stock, thereby producing alternatives in favor of sustainable materials.

Herein, we report a novel type of symmetrical trithiocarbonate chain transfer agent (CTA) based diphenylmethyl as R groups. The utilization of this CTA in the Reversible Addition-Fragmentation chain Transfer (RAFT) process reveals an efficient control in the polymerization of methacrylic monomers and the preparation of block copolymers. The latter are obtained by the (co)polymerization of styrene or butyl acrylate using a functionalized macro-CTA polymethyl methacrylate (PMMA) previously synthesized. Data show low molecular weight dispersity values (Đ &lt, 1.5) particularly in the polymerization of methacrylic monomers. Considering a typical RAFT mechanism, the leaving groups (R) from the fragmentation of CTA should be able to re-initiate the polymerization (formation of growth chains) allowing an efficient control of the process. Nevertheless, in the case of the polymerization of MMA in the presence of this symmetrical CTA, the polymerization process displays an atypical behavior that requires high [initiator]/[CTA] molar ratios for accessing predictable molecular weights without affecting the Đ. Some evidence suggests that this does not completely behave as a common RAFT agent as it is not completely consumed during the polymerization reaction, and it needs atypical high molar ratios [initiator]/[CTA] to be closer to the predicted molecular weight without affecting the Đ. This work demonstrates that MMA and other methacrylic monomers can be polymerized in a controlled way, and with “living” characteristics, using certain symmetrical trithiocarbonates.

Ibuprofen-loaded polymeric particles with around 9.2 nm in mean diameter, as determined by electron microscopy, dispersed in an aqueous media containing up to 12.8% solids were prepared by semicontinuous heterophase polymerization. The polymeric material is a (2/1 mol/mol) methyl methacrylate-co-methacrylic acid copolymer similar to Eudragit S100, deemed safe for human consumption and used in the manufacturing of drug-loaded pills as well as micro- and nanoparticles. The loading efficiency was 100%, attaining around 10-12% in drug content. Release studies showed that the drug is released from the nanoparticles at a slower rate than that in the case of free IB. Given their size as well as the pH values required for their dissolution, it is believed that this type of particles could be used as a basis for preparing nanosystems loaded with a variety of drugs.

Thermoplastic vulcanizates (TPVs) based on high density polyethylene (HDPE), ethylene propylene diene terpolymer (EPDM) were reinforced with ground tyre rubber (GTR) modified with sulfuric acid and dynamically vulcanized with dicumyl peroxide (DCP). TPVs were composed by 40% of HDPE, 30% of EPDM and 30% of GTR at 50 and 100 mesh and the concentration of DCP was varied from 0.3 to 3.6 parts per hundred rubber (phr). The properties of the TPVs containing GTR were determined by infrared spectroscopy, gel content and differential scanning calorimetry (DSC) analyses. The mechanical properties of the composites were also obtained. An increase of about 207% in the Young's modulus was obtained in blends containing GTR modified with sulfuric acid (GTR-SA) in relation with blends containing pristine GRT. Good compatibility of compounds containing GTR-SA was observed, GTR-SA presented high specific area as a consequence of the modification with sulfuric acid. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers

In a first step, 1,3-butadiene was selectively polymerized at 60°C in styrene as solvent using NdV3/DIBAH/EASC as the catalyst system. The catalyst system activation process, the addition order of monomers and catalyst components, and the molar ratios [Al]/[Nd] and [Cl]/[Nd] were studied. The catalyst system allowed the selective 1,3-butadiene polymerization, reaching conversions between 57.5 and 88.1% with low polystyrene contents in the order of 6.3 to 15.4%. Molecular weights ranging from 39,000 to 150,000 g/mol were obtained, while cis-1,4 content was found in the interval of 94.4 to 96.4%. On the other hand, the glass transition temperatures of synthesized materials were established in the range of −101.9 to −107.4°C, explained by the presence of polystyrene segments in the polybutadiene chains; in the same sense, the polybutadienes did not show the typical melting endotherm of high cis-polybutadienes. In a second step, the resulting styrene/high cis-1,4 polybutadiene solutions were used to synthesize ABS (adding a fraction of acrylonitrile monomer) and HIPS via in situ bulk polymerizations and the results were discussed in terms of morphological development, molecular parameters, dynamical mechanical behavior, and mechanical properties.

Different rubbers based on polybutadiene were synthesized in solution by the reversible addition-fragmentation chain-transfer polymerization (RAFT) technique using 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl] entanoic acid as RAFT agent and 1,1’-azobiscyclohexanecarbonitrile (Vazo-88) as initiator. The results obtained in the polymerization of polybutadiene and poly(butadiene-co-acrylonitrile) (NBR) are discussed in terms of molecular weight distribution, composition and microstructure. Composition of polybutadiene in NBR´s was kept constant along the copolymerization, and the vinyl, cis and trans isomers are shown in values of around 12, 26 and 62% in all cases. Resulting rubbers were used to synthesize acrylonitrilebutadiene-styrene (ABS) type resins through an in situ bulk polymerization. Dynamic-mechanical properties and the morphology were analyzed in all the different ABS resins. In DMA analyses, the rubber component presented two transitions as well as an increase in the magnitude of the transition located around -75 °C, which is explained by the significant amount of SAN occlusions in the morphology, analyzed by TEM.

Polyethylene/waste tire dust (WTD) composites were obtained by an in situ polymerization technique. The surface of the WTD was modified with deposition of polyethylene by using plasma polymerization. Ethylene polymerization was carried out using bis(cyclopentadienyl) titanium dichloride (Cp2TiCl2) as homogeneous metallocene catalyst, while diethylaluminum chloride (DEAC), ethylaluminum sesquichloride (EASC) and methyl aluminoxane (MAO) were used as co-catalysts at two different [Al]/[Ti] molar ratio. The main characteristics of the obtained polyethylenes were determined by size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction. The results showed that by using EASC and MAO the highest catalytic activities were presented at a [Al]/[Ti] molar ratio of 9.17 and 18.33 respectively. Even though it was possible to obtain polyethylene using WTD (modified or unmodified) the catalytic activity was lower than in the case in which no WTD was added in ethylene polymerization. Scanning transmission electronic microscopy images evidenced that the original morphology of the polyethylenes was not modified by the presence of WTD.

A study on the geometry of antennas is proposed in order to find those that provide the optimal conditions of operation for applications in the terahertz range. We used an analysis based on evolutionary algorithms for that purpose, showing that the optimal geometries are not similar to those used in radio frequency applications.

1,3-Butadiene monomer was polymerized at 40°C and 60°C by means of a catalyst comprising neodymium (Nd) chloride/1-pentanolate/triisobutylaluminum (TIBA) in cyclohexane as solvent; the catalyst system was aged at 5 and 30 min. The effects on conversion, catalytic activity and polymer final properties were evaluated. The obtained polybutadienes (PBs) were characterized by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) techniques and the results were discussed in terms of the effect of aging time and reaction temperature.

We compared 9 × 9 arrays of bimetallic Ni(Nickel)-Pt(Platinum) nanoantennas for a classic and evolutive dipole configuration. We fabricated the nanoantennas by e-beam lithography and characterized them with a solar simulator to analyze the I − V curves. From these curves, a thermoelectric voltage dependence associated by classic and evolutive dipole configuration was observed. We show that the evolutive dipole nanoantennas (EDN) generate up to three times more voltage in contrast with the classic dipole nanoantenna (CDN). Indeed, the evolutive configuration is 1.3 times more efficient than its classical counterpart. The results are corroborated by absorbance of these nanoantennas in the 20 to 36 THz range, where EDN is 40% more efficient than CDN and 30% in the range of 36.1 to 90 THz. Moreover, the experimental results match the thermoelectric behavior obtained using numerical simulations. The EDN can be used in applications ranging from aerospace technology to energy harvesting, photodetector, and sensors, where high thermoelectric efficiency is needed.

Chitosan-coated magnetic nanoparticles (CMNP) were obtained at 70 °C and 80 °C in a one-step method, which comprises precipitation in reverse microemulsion in the presence of low chitosan concentration in the aqueous phase. X-ray diffractometry showed that CMNP obtained at both temperatures contain a mixture of magnetite and maghemite nanoparticles with ≈4.5 nm in average diameter, determined by electron microscopy, which suggests that precipitation temperature does not affect the particle size. The chitosan coating on nanoparticles was inferred from Fourier transform infrared spectrometry measurements; furthermore, the carbon concentration in the nanoparticles allowed an estimation of chitosan content in CMNP of 6%-7%. CMNP exhibit a superparamagnetic behavior with relatively high final magnetization values (≈49-53 emu/g) at 20 kOe and room temperature, probably due to a higher magnetite content in the mixture of magnetic nanoparticles. In addition, a slight direct effect of precipitation temperature on magnetization was identified, which was ascribed to a possible higher degree of nanoparticles crystallinity as temperature at which they are obtained increases. Tested for Pb2+ removal from a Pb(NO3)2 aqueous solution, CMNP showed a recovery efficacy of 100%, which makes them attractive for using in heavy metals ion removal from waste water.

Summary: The anionic and Ziegler-Natta polymerizations of 1,3-butadiene initiated with n-BuLi and NdV/TIBA/DEAC respectively were carried out in presence of ionic liquids and cyclohexane as solvent in both cases. Polybutadienes obtained were characterized by SEC, NMR and DSC techniques and results were compared with polybutadienes synthesized under similar conditions but in absence of ionic liquids. In all cases, the presence of ionic liquids caused a decrease in the reaction exothermal and also a diminution in the molecular weight distribution. The ionic liquids increased the microstructure cis-1,4 in both kind of polymerizations, and promotes a shift towards lower temperatures in the glass-transition temperature.

Summary: A new lumping-based approach for calculating the molecular weight distribution (MWD) in polymerization systems is proposed. In order to illustrate its applicability the proposed methodology is used for modelling the kinetics of a 1,3-diene polymerization using a binary neodymium-based catalytic system. The model is capable of reproducing experimental data after fitting for the evolution of molecular weight and polydispersity. The results of this preliminary simulation are used as a guide to design kinetics experiments that may lead to improve the kinetic model and to deepen the knowledge of the system under study.