Nara Regina de Souza Basso

Synthesis and NMR characterization of aliphatic-aromatic copolyesters by reaction of poly(ethylene terephthalate) post-consumer and poly(ethylene adipate)

An aliphatic-aromatic copolyester of poly(ethylene terephthalate), PET, and poly(ethylene adipate), PEA, PET-co-PEA, was synthesized by the high temperature melt reaction of post-consumer PET and PEA. As observed by NMR spectroscopy, the reaction yielded random copolyesters in a few minutes through ester-interchange reactions, even without added catalyst. The copolyesters obtained in the presence of a catalyst presented higher intrinsic viscosity than that obtained without the addition of catalyst, due to simultaneous polycondensation and ester-interchange reactions. The structure of the aliphatic-aromatic copolyesters obtained in different PET/PEA ratio is random as observed by NMR analysis.

Transient modulation of acetylcholinesterase activity caused by exposure to dextran-coated iron oxide nanoparticles in brain of adult zebrafish.

Superparamagnetic iron oxide nanoparticles (SPIONs) are of great interest in nanomedicine due to their capability to act simultaneously as a contrast agent and as a targeted drug delivery system. At present, one of the biggest concerns about the use of SPIONs remains around its toxicity and, for this reason, it is important to establish the safe upper limit for each use. In the present study, SPION coated with cross-linked aminated dextran (CLIO-NH₂) were synthesized and their toxicity to zebrafish brain was investigated. We have evaluated the effect of different CLIO-NH₂ doses (20, 50, 100, 140 and 200 mg/kg) as a function of time after exposure (one, 16, 24 and 48 h) on AChE activity and ache expression in zebrafish brain. The animals exposed to 200 mg/kg and tested 24 h after administration of the nanoparticles have shown decreased AChE activity, reduction in the exploratory performance, significantly higher level of ferric iron in the brains and induction of casp8, casp 9 and jun genes. Taken together, these findings suggest acute brain toxicity by the inhibition of acetylcholinesterase and induction of apoptosis.

TEREPHTHALIC ACID, NEOPENTYL GLYCOL AND TRIMETHYLOLPROPANE POLYESTERIFICATION USING VERSATILE AND HIGHLY EFFICIENT TIN COMPLEXES AS CATALYSTS PRECURSORS

The catalytic performance of the tin complexes bis(acetylacetonato)tin(II) (1), dibutyltin oxide (2), bis(chloroacetato)tin(II) (3), bis(3-hydroxy-2-methyl-4-pyrona)tin(II) (4), dibenzoatotin(II) (5) and dihydroxybutyltin chloride (6) are described for terephthalic acid, neopentyl glycol and trimethylolpropane polyesterification. The synthesized complexes, which are easy to prepare from inexpensive commercial chemicals, showed catalytic behavior comparable to the industrially used (2) and (6). The productivity values varied from 72.2 when (2) was used as a catalyst to 192.0 with (1). The best values for reaction time was obtained for the commercial catalyst (6) (6 h 26 min) and for (1) (7 h 36 min). The infrared analyses allowed us to observe bands relative to ester formation and to confirm the hydroxylation for all polymers samples. 1. INTRODUTION Polyesters have been widely used as polymeric materials. Indeed, terephthalic acid based polyesters have received special attention due to several interesting properties of Polyethylene terephthalate) or PET. This polyester is the most widely used synthetic fiber which is sold under many different trade names. PET is also commonly encountered in plastic bottles for soft drinks and in films which are used for food or liquid packaging, magnetic tapes and novelty balloons, among others applications [1], Polyesters based on isophthalic acid and terephthalic acid have been developed for use in polyester powder coatings [2]. Terephthalic acid has historically been the primary monomer providing polymers with the required glass transition temperature for coating storage stability, while contributing flexibility, weathering and chemical resistance [2]. Different metallic ions have been described that catalyse efficiently esterification and polyesterification reactions. Nondek and Mälek [3] ordered the activities of catalysts for reaction of ethylene glycol with isophthalic acid as Sn> T i 4 + »Zn >Pb,Co,Cd. The development of simple and cheaper catalytic systems for polyesterification reaction as well as new polymer materials using different monomers is important for technological and academic purposes. We have recently shown that the tin complex, bis(3hydroxy-2-methyl-4-pyrona)tin(II) (4), is highly active as polyesterification catalyst [4], In this paper we wish to report highly efficient catalysts systems based upon tin complexes, using differents ligands, for terephthalic acid (TFA), neopentyl glycol (NPG) and trimethylolpropane (TMP) polyesterification. 2. MATERIALS AND METHODS 2.1. General Procedures Routine infrared spectra were recorded on a Bomenn MB-Series Hartmann & Braun spectrophotometer. Molecular weights of the polymers were determined by gel permeation chromatography with a GPC Data Station 4.0. The acid number, i.e, the total concentration of the carboxylic groups in the reaction medium, are measured by diluting about 1.0 g of the sample in 50cm DMF. The sample is heated until fusion without boiling. Then the sample is cooled at room temperature and titrated with 0.1 Ν KOH in methanol with Phenolphthalein as indicator. The acid number [5] is calculated by (AN=V(mL) χ 56.1 χ N)/P[mgKOH/g] were V= volume of titrate liquid; N= Normality of titrate liquid and P= sample mass viscosity. 2.2. Preparation of the catalysts The complexes, (1), (3) , (4) and (5) were prepared according the procedures described in the literature [6,7,4,8], The catalysts (2) and (6) were obtained from commercial sources and used as received without further purification. 2.3. Polymerization Reactions Polymerization was carried out in a 2L reactor system consisting of a four necked round-bottom flask. The flask was equipped with an air-driven stirrer, a thermocouple, nitrogen inlet tube and two adjacent partial reflux condensers one of them charged with a packing, and the other a steam-jacketed partial reflux condenser. A tube test receiver is installed in one of the four necks. The flask is heated by means of an electrical heating mantle. The temperature is monitored via an Pt 100 thermocouple with a temperature

Polyethylene-polyaniline Nanofiber Composites: Evaluation of Experimental Conditions of in situ Polymerization

The difficult processability of polyaniline (PAni) can be overcome by preparing composites with high density polyethylene (HDPE), resulting in a conducting material with improved mechanical properties. PAni nanofibers were synthesized in this research using a rapid mixing method, while HDPE/PAni composites were prepared by in situ polymerization using Cp2ZrCl2/MAO as a catalyst system. Different experimental conditions for polymerization and an electrochemical study were performed. The findings confirmed that the addition of small amounts of Pani (up to 7%) and longer impregnation (120 min) with methylaluminoxane (MAO) before polymerization are important factors contributing to increased catalytic activity. Analysis by cyclic and differential pulse voltammetry indicates that MAO reacts with the PAni in the ethylene polymerization process, and forms active species in the presence of the catalyst. Changes in catalytic activity may be due to the kinetic consumption of the active species, which become less important in the presence of PAni.

A VERSATILIDADE DOS COMPOSTOS DE COORDENAÇÃO NA PRODUÇÃO DE POLIETILENOS: UMA REVISÃO DOS SISTEMAS CATALÍTICOS

Taking into account the relevance of polyethylene for modern society and the role of catalysts for the production of this material, in the present work, we carried out a review of the main catalytic systems used in industry and academia. Most systems consist of coordination compounds, whose structural versatility allows the tuning of the characteristics of polyethylene for different applications. The structural aspects and chemical reactivity of such systems are discussed based on the existing literature and experimental data.

A New Post-Metallocene-Ti Catalyst with Maltolate Bidentade Ligand: an Investigation in Heterogeneous Polymerization Reactions in Different Mesoporous Supports

A new titanium catalyst easily synthesized from ethylmaltol bidentate chelator ligand was studied in homogeneous and heterogeneous ethylene polymerization. The dichlorobis(3-hydroxy-2-ethyl-4-pyrone)titanium(IV) complex was characterized by 1H and 13C NMR (nuclear magnetic resonance), UV-Vis and elemental analysis. Theoretical study by density functional theory (DFT) showed that the complex chlorines exhibit cis configuration, which is important for the activity in olefin polymerization. The complex was supported by two methods, direct impregnation or methylaluminoxane (MAO) pre-treatment, in five mesoporous supports: MCM-41 (micro and nano), SBA-15 and also the corresponding modified Al species. All the catalytic systems were active in ethylene polymerization and the catalytic activity was strongly influenced by the method of immobilization of the catalyst and the type of support.

Cashew nut shell liquid, a valuable raw material for generating semiconductive polyaniline nanofibers

Cashew nut shell liquid (CNSL) is an abundant and renewable by-product of the cashew nut industry. It appears to be a valuable raw material for generating semiconductive polyaniline (PAni) nanomaterial with enhanced thermal stability and well-defined nanofiber morphology following a polymerization dispersion process. This study confirms that CNSL acts as a soft template during PAni synthesis, leading to an improvement in the nanofiber aspect. CNSL also improves the thermal stability of the PAni nanomaterial. Moreover, CNSL is an effective surfactant that promotes and stabilizes the dispersion of PAni nanofibers within water, allowing the more ecofriendly preparation of PAni nanomaterial by substituting the commonly used organic solvent with aqueous media. Finally, although CNSL promotes the formation of the conductive emeraldine salt form of PAni, increasing CNSL concentrations appear to plasticize the PAni polymer, leading to reduced electrical conductivity. However, this reduction is not detrimental, and PAni nanofibers remain semiconductive even under high CNSL concentrations.

Design and optimization of biocompatible polycaprolactone/poly (l-lactic-co-glycolic acid) scaffolds with and without microgrooves for tissue engineering applications: DESIGN AND OPTIMIZATION OF BIOCOMPATIBLE PCL/PLGA SCAFFOLDS

This study investigated the effects of smooth and microgrooved membrane blends, with different polycaprolactone (PCL)/ poly(lactic-co-glycolic acid) (PLGA) ratios on the viability, proliferation, and adhesion of different mammalian cell types. The polymer matrices with and without microgrooves, obtained by solvent casting, were characterized by field-emission scanning electron microscopy, atomic force microscopy, contact angle and Youngs modulus. Blend characterization showed an increase in roughness and stiffness of membranes with 30% PLGA, without any effect on the contact angle value. Pure PCL significantly decreased the viability of Vero, HaCaT, RAW 264.7, and human fetal lung and gingival fibroblast cells, whereas addition of increasing concentrations of PLGA led to a reduced cytotoxicity. Increased proliferation rates were observed for all cell lines. Fibroblasts adhered efficiently to smooth membranes of the PCL70/PLGA30 blend and pure PLGA, compared to pure PCL and silicone. Microgrooved membranes promoted similar cell adhesion for all groups. Microstructured membranes (15 and 20-μm wide grooves) promoted suitable orientation of fibroblasts in both PCL70/PLGA30 and pure PLGA, as compared to pure PCL. Neuronal cells of the dorsal root ganglion exhibited an oriented adhesion to all the tested microgrooved membranes. Data suggest a satisfactory safety profile for the microgrooved PCL70/PLGA30 blend, pointing out this polymer combination as a promising biomaterial for peripheral nerve regeneration when cell orientation is required.

New Isopropylmaltol - Ti Synthesis and its Use as a Catalyst for Olefin Polymerization

This report describes a new synthesis of isopropylmaltol from furfural. This organic compound was used as ligand to obtain a new complex, the dichlorobis-(3-hydroxy-2-isopropyl-4-pyrone) titanium(IV). 1H nuclear magnetic ressonance, elemental analysis and UV-Vis analysis confirm the complex formation. This complex was investigated in ethylene polymerization using methylaluminoxane (MAO) as cocatalyst. The catalytic activity was low, however, there were obtained very high molecular weight polyethylenes, which are interesting for various special applications.

The use of crude tall oil as feed-stock for alkyd resins

Abstract The synthesis of modified alkyd resins using a crude tall oil with a content of rosin acids of 39.8 % is described. This material has the composition of fatty acids close to soybean oil, has low cost and is widely available being a forest product industrial residue. The synthetic route includes the reaction of tall oil and maleic anhydride, in the presence of the catalyst (LiOH), followed by polyesterification reaction steps, resulting in an alkyd resin with interesting properties. The acid value (AN) and viscosity were used to follow the reaction, and it appears to be dependent upon the polyalcohol used in the polyesterification step. A period of 15 hours was needed to yield a tack-free coating.