Fabrication of Barium Strontium Titanate (Ba0.6Sr0.4 TiO3) 3D Microcomponents from Aqueous Suspensions

This study reports on the fabrication of BST (Ba_0.6Sr_0.4TiO₃)‐based 3D microcomponents through an aqueous colloidal approach. The BST powder was synthesized by solid‐state reaction assisted by thermal analysis and XRD diffraction. Well crystalline cubic BST single phase was obtained upon heat‐treating the precursor powder mixture at 1200°C–1250°C. The reactivity of the BST powder toward water was evaluated by the changes in pH and concentration of leached ionic species along aging time. Hydrolysis reactions were suppressed by chemisorbing a suitable phosphate‐based protective agent and enabled an excellent dispersion ability to be achieved. Aqueous suspensions with solids loadings as high as 50 vol% that are stable against hydrolysis for several days could easily be prepared from the surface‐treated BST powder in aqueous solutions of an epoxy resin. After adding a suitable hardener, the colloidal suspensions could easily be cast into soft silicon rubber molds to obtain homogeneous and high dense green BST bodies.     

Investigation of cure kinetics in epoxy/multiwalled carbon nanotube nanocomposites

With the increased interest in thermoset resin nanocomposites, it is important to understand the effects of the material on nanoscale characteristics. In this study, a curing reaction of an epoxy resin, which contained 0.25, 0.50, or 1.00 wt % of multiwalled carbon nanotubes (MWCNTs), at different heating rates was monitored by differential scanning calorimetry; cure kinetics were also evaluated to establish a relationship between crosslinking (network formation) and mechanical properties. MWCNT concentrations above 0.25 wt % favored crosslinking formation and decreased the activation energy (E_a) in the curing reaction. Examination of the kinetic mechanism suggests that the MWCNT locally restricted the spatial volume and favored the formation of nodular morphology in the resin, especially for high MWCNT concentrations. The MWCNT exhibited some entanglement in the matrix, which hindered a more pronounced effect on the mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39857.     

Analysis of polyolefin compositions through near infrared spectroscopy

In this work, NIRS is employed to provide compositions of α‐olefin copolymers, allowing for evaluation of the effects of certain key process variables on the final NIR spectral responses of obtained polymer materials. This work also introduces a new temperature programmed analytical technique, which combines NIRS measurements with partial fractionation of α‐olefin copolymers. The new proposed technique can be used for evaluation of polyolefin compositions, as presented here for poly(propene/1‐butene) copolymers. Besides, preliminary results obtained from thermal fractionation experiments indicate that this new proposed experimental technique can be employed for characterization of comonomer sequence distributions of α‐olefin copolymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40127.     

Formal [3+2] Annulation Involving Allylic Bromides and Thioureas. Synthesis of 2‐Iminothiazolidines through a Base‐Catalyzed Intramolecular anti‐Michael Addition

A simple and efficient protocol was developed for the synthesis of 2‐iminothiazolidines through a base‐mediated [3+2] annulation involving substituted thioureas and allylic bromides bearing electron‐withdrawing groups. This domino process consists of nucleophilic displacement, followed by intramolecular anti‐Michael addition of the preformed allylic isothiourea under mild conditions to give the thiazolidine core.

     

NSAID-Based Coordination Compounds for Biomedical Applications: Recent Advances and Developments

After the serendipitous discovery of cisplatin, a platinum-based drug with chemotherapeutic effects, an incredible amount of research in the area of coordination chemistry has been produced. Other transition metal compounds were studied, and several new relevant metallodrugs have been synthetized in the past few years. This review is focused on coordination compounds with first-row transition metals, namely, copper, cobalt, nickel or manganese, or with zinc, which have potential or effective pharmacological properties. It is known that metal complexes, once bound to organic drugs, can enhance the drugs’ biological activities, such as anticancer, antimicrobial or anti-inflammatory ones. NSAIDs are a class of compounds with anti-inflammatory properties used to treat pain or fever. NSAIDs’ properties can be strongly improved when included in complexes using their compositional N and O donor atoms, which facilitate their coordination to metal ions. This review focuses on the research on this topic and on the promising or effective results that complexes of first-row transition metals and NSAIDs can exhibit.     

A New Process for Obtaining Inverted Sugar Using Carbon Dioxide

It has been found that carbon dioxide gas is an efficient acid-catalyst to promote hydrolysis of a solution of sucrose. The conditions for this reaction to proceed have been found to be dependent on the partial pressure of the gas.