Screening of coformers for quercetin cocrystals through mechanochemical methods

Quercetin (QUE) is a nutraceutical compound that exhibits pharmacological properties such as antioxidant, cardioprotective, anti-ulcer, and anti-inflammatory effects. Although QUE is well-known for its benefits, its efficacy is limited due to low solubility. Thus, cocrystallization acts as an interesting approach to improve the solubility�among other properties�of this compound. In this work, cocrystallization screening was applied through neat grinding (NG) and liquid-assisted grinding (LAG), in which QUE and four cocrystal formers (benzamide,�picolinamide, isonicotinamide, and pyrazinoic acid) were tested. The precursors and QUE-coformer systems were characterized using thermoanalytical techniques (TG-DTA), X-ray powder diffraction (XRPD), and Fourier transform infrared (FTIR) spectroscopy. The results showed the formation of QUE cocrystals with picolinamide and isonicotinamide coformers in a 1:1 stoichiometric ratio. Furthermore, although coformers are isomers, spectroscopic and thermal data suggest that the supramolecular synthons involved in cocrystallization are different.

Aplicação de técnicas termoanalíticas (TGA/DTA) para avaliação do comportamento térmico de amostras de argilas para obtenção de pozolanas

The search for materials that are used in sustainable construction, both from the environmental point of view and in relation to durability and resistance, has been the subject of much research. Thermally activated clays have gained importance as a source of supplemental cementitious material as they have environmental advantages such as reduced CO2 emissions, economical due to reduced energy consumption for cement production, and techniques as they improve strength. and the durability of concrete and mortar, as well as abundance in nature. In this work, the thermal behavior of three clay samples from the south coast of Paraíba is evaluated. The clay samples were subjected to heat treatment at temperatures of 600 ºC, 700 ºC and 800 ºC and analyzed with thermoanalytical techniques (TGA / DTA). The clays were physicochemically and mineralogically characterized before and after the heat treatment and were classified as type N pozzolanic material, according to the chemical requirements of NBR 12653/2015 and, the thermal studies of clay soil samples indicate that in calcination temperatures of 600 °C and 800 °C the observed mass losses were very small, about 2%, while at the calcination temperature of 700 °C large mass losses were observed, mainly for JPS2 and JPS3 samples, values of 7.41% and 11.02%, respectively.

Additive manufacturing of functional polymer-based composite with enhanced mechanoluminescence (ZnS:Mn) performance

Triboluminescence (TL) is a phenomenon of light emission induced by impact, stress, fracture, or an applied mechanical force. This phenomenon can be used to detect, evaluate, and predict mechanical failures in composites. In this report, we utilized manganese-doped zinc-sulphide (ZnS: Mn) and Polystyrene (PS) composite to fabricate a TL functional part via additive manufacturing. The morphology of the particles inside the polymer matrix were studied using scanning electron microscopy and micro CT scan. Thermoanalytical techniques such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were carried out to evaluate the thermal transitions and degradation of the composites. The mechanoluminescence performance of the printed samples is evaluated by three-point flexural test and observed to depend on processing conditions that can be utilized to achieve a strong light signal at different mechanical loads. The polymer composite fabrication and processing reduced particle size, enhanced particle dispersion, and altered the mechanical properties of the polymer to help increase the mechanoluminescence response up to 10 times in the 3D printed parts. The unique mechanoluminescence properties of 3D printed luminescent composite have great potential for structural monitoring applications.

Advanced Isoconversional Kinetic Analysis for the Elucidation of Complex Reaction Mechanisms: A New Method for the Identification of Rate-Limiting Steps

Two complex cure mechanisms were simulated. Isoconversional kinetic analysis was applied to the resulting data. The study highlighted correlations between the reaction rate, activation energy dependency, rate constants for the chemically controlled part of the reaction and the diffusion-controlled part, activation energy and pre-exponential factors of the individual steps and change in rate-limiting steps. It was shown how some parameters computed using Friedman’s method can help to identify change in the rate-limiting steps of the overall polymerization mechanism as measured by thermoanalytical techniques. It was concluded that the assumption of the validity of a single-step equation when restricted to a given α value holds for complex reactions. The method is not limited to chemical reactions, but can be applied to any complex chemical or physical transformation.

Characterization, Purity Determination and Decomposition Kinetics of Ezetimibe Under Non-Isothermal Conditions

Background:Ezetimibe is a lipid-lowering agent used therapeutically alone or in combination of other drugs. The properties of the solid-state of drugs are critical factors in the pharmaceutical formulation development. Several instrumental techniques can be employed in the analysis of new formulations, but the thermoanalytical techniques, provide a fast and careful evaluation of physicochemical properties of a compound. </P><P> Objective: To carry out the physicochemical characterization, purity evaluation and non-isothermal kinetic studies of ezetimibe raw material.Methods:A combination of the following different analytical technics was employed: Differential Scanning Calorimetry, Thermogravimetric, Scanning Electron Microscopy, X-ray powder diffraction.Results:The results evidenced the crystalline characteristic of ezetimibe. The sample purity was 99.06 % ± 0.02 and the thermal decomposition followed a zero order kinetic, with activation energy of 96.56 kJ mol–1 and Arrhenius frequency factor of 3,442 x 109 min-1.Conclusion:The characterization of ezetimibe together with the non-isothermal kinetic degradation represents important studies for the pharmaceutical area, since it provides crucial information for the pharmacotechnical/quality control/production areas that should establish the specifications necessary to standardize the requirements of the raw material acquire to ensure the batch-to-batch reproducibility.