Microwave assisted polycondensation of polyimides by [4,4′‐(hexafluoroisopropylidene)diphthalic anhydride,pyromellitic dianhydride] and [2,4,6‐trimethyl‐m‐phenylenediamine]. Power,time, and solvent effect

The microwave assisted polycondensation of two polyimides were studied using pyromellitic dianhydride (PMDA), and 4,4′‐(hexafluoroisopropyliden)diphthalic anhydride (6FDA) as dianhydride monomers and 2,4,6‐trimethyl‐m‐phenylenediamine (TrmPD), as diamine monomer, under microwave irradiation in DMF and DMSO solvents. The structure and performance of polymers were characterized by Fourier Transform Infrared Spectroscopy (FTIR), viscosity, density, and Thermogravimetric Analysis (TGA). The results show that the polyimides can be obtained in a short reaction time with high intrinsic viscosity and high yield. The effect of the presence of a bridging group, ? C(CF₃)₂? , in the monomer structure is apparent in the permeability parameters of the macromolecules as polymer (6FDA‐TrmPD) always presents better results than polymer (PMDA‐TrmPD). Properties as density and T_g increases with the time exposition to the microwave irradiation. Polyimides obtained present good thermal properties because they began to lose weight in a range of 8–16% at high temperature as 450°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Combined Thermometric Analysis of a Series of Highly Dealuminated USY Zeolites

A transient reactor model was used to consolidate and quantify the data of ammonia adsorption microcalorimetry and single ammonia TPD runs, using several members of the commercial CBV series of dealuminated HY zeolites. The model accounts for the competitive re-adsorption of molecules desorbing from multiple sites, using the microcalorimetric data to constrain the desorption energy parameters to physically meaningful values. All TPD profiles were well represented by models consisting of only two or three distinct site types, even though the differential heat plots imply a continuous distribution of sites in the 160-80 kJ/mol range for all catalysts. Increasing dealumination severity is evidenced by a decrease in total site density for sites 100 kJ/mol. While there was no evidence of an enhancement of adsorption strength within the series studied, the range of site strengths available remained the same. There is correspondence between the density of adsites = 100 kJ/mol and the framework Al³⁺ concentration, although the ratio of these is less than one, even for Si/Al80. The inherent limits in using ammonia adsorption as an acidity probe are briefly mentioned.     

Structural and chemical transformations in SnS thin films used in chemically deposited photovoltaic cells

Chemically deposited SnS thin films possess p-type electrical conductivity. We report a photovoltaic structure: SnO₂:F-CdS-SnS-(CuS)-silver print, with V_oc > 300 mV and J_sc up to 5 mA/cm² under 850 W/m² tungsten halogen illumination. Here, SnO₂:F is a commercial spray-CVD (Pilkington TEC-8) coating, and the rest deposited from different chemical baths: CdS (80 nm) at 333 K, SnS (450 nm) and CuS (80 nm) at 293-303 K. The structure may be heated in nitrogen at 573 K, before applying the silver print. The photovoltaic behavior of the structure varies with heating: V_oc ≈ 400 mV and J_sc < 1 mA/cm², when heated at 423 K in air, but V_oc decreases and J_sc increases when heated at higher temperatures. These photovoltaic structures have been found to be stable over a period extending over one year by now. The overall cost of materials, simplicity of the deposition process, and possibility of easily varying the parameters to improve the cell characteristics inspire further work. Here we report two different baths for the deposition of SnS thin films of about 500 nm by chemical deposition. There is a considerable difference in the nature of growth, crystalline structure and chemical stability of these films under air-heating at 623-823 K or while heating SnS-CuS layers, evidenced in XRF and grazing incidence angle XRD studies. Heating of SnS-CuS films results in the formation of SnS-Cu_xSnS_y. ‘All-chemically deposited photovoltaic structures’ involving these materials are presented.     

Development and characteristics of biodegradable Aloe‐gel/egg white films

The use of synthetic nonbiodegradable polymers has led to environmental damage. This has encouraged the interest to the development of new renewable and biodegradable matrices. The potential of egg white (EW) protein for the development of bioplastic materials has been published. However, the mixture of EW with Aloe‐gel (AG) for film formation has not been documented. In this study, films with different EW and AG combinations are manufactured and their properties are analyzed. In general, the AG/EW films are homogeneous, smooth, with no pores and with cumulus of protein on the surface with better extensibility, plasticity, and low tensile strength. In addition, they are yellow colored, UV‐light blocker, with high solubility (2.2 times) and high Water Vapor Permeability (4.17 times) compared with the control (EW film). The AG/EW films showed higher percentage of soluble protein and antibacterial activity than the control. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44067.     

Mechanosynthesis of 2,2′-((1E,1′E)-(2,5-bis(octyloxy)-1,4-phenylene)bis(ethene-2,1-diyl))bis(6-bromoquinoline): optical,electroluminescence, electrical,electrochemical, and morphological studies

In this work is report the synthesis by mechanochemical method of a small molecule of the oligophenylene (bisquinoline) design (OBM), excellent optical and electrical properties, and potential use as an electroluminescent material in the form of a nano-film in the manufacture of an organic light-emitting diode (OLED). OBM was synthesized by a Knoevenagel condensation reaction and was chemically characterized by ¹H-NMR, ¹³C-NMR, FT-IR spectroscopy, and AccuTOF-DART mass spectrometry. UV–Vis and fluorescence spectroscopies were used to obtain the optical properties of OBM, both in solution and in film. Also, the OBM film was examined by atomic force microscopy and showed a high degree of homogeneity which allowed the manufacture of an OLED device with ITO/OBM/PEDOT: PSS/Al configuration with a luminance of 2350 cd/m² when supplied with a fixed current of 15 mA and 10 volts.

     

Metal ion retention using the ultrafiltration technique: Preparation,characterization of the water-soluble poly(1-vinyl-2-pyrrolidone-co-itaconic acid) and its metal complexes in aqueous solutions

Radical copolymerization of 1-vinyl-2-pyrrolidone with itaconic acid at different feed monomer ratios (75–25 mol %) were investigated. The copolymers were characterized by elemental analysis, Fourier transform infrared (FTIR), ¹H and ¹³C NMR spectroscopy. The copolymer composition was determined from elemental analysis and found to be statistical copolymers. Additionally, viscosimetric measurements, molecular weight, and polydispersity have been determined. The metal complexation of poly(1-vinyl-2-pyrrolidone-co-itaconic acid) for the metal ions such as Cr(III), Co (II), Zn(II), Ni(II), Cu(II), Cd(II), and Fe(III) were investigated at pH 3, 5, and 7 in aqueous solution. The metal ion interaction with hydrophilic polymers was determined as a function of the pH and filtration factor. Poly(1-vinyl-2-pyrrolidone-co-itaconic acid) showed a high affinity for the metal ions at pH 5 and 7. The poly(NVP-co-IA), with a copolymer composition of 29 : 71 mol % (PVA-3), presented the highest metal ion retention values, particularly at higher pHs, at which the carboxylic acid groups are nonprotonated and could easily coordinate with the metal ions. According to the interaction pattern obtained, Cr(II), Zn(II), Pb(II), and Ni(II) formed the most stable complexes at pH 7. The thermal behaviors of the copolymer and polymer metal complex were characterized using differential scanning calorimetry (DSC) and thermogravimetry techniques under nitrogen atmosphere. The copolymers present high thermal stability and do not present glass transition in DSC curves between 25 and 500°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Isolation and Characterization of Starch from Seeds of Araucaria brasiliensis: A Novel Starch for Application in Food Industry

The pinhão seeds (Araucaria angustifolia), are composed of 34% of starch and very low fractions of protein, lipids and phenolic compounds. This composition is favorable to obtain a stable, white in color and odorless starch, useful in the food industry. The isolated starch is constituted predominantly of small‐sized round granules (10–25 μm), rather than oval ones. Compared to corn starch, pinhão starch has a lower temperature and enthalpy of gelatinization. Retrogradation occurs to a lower extent in pinhão starch, due to its lower amylose content (∼25%). The pasting profile of pinhão starch showed a higher consistency than that of corn starch, with lower temperature in the peak of maximum viscosity. The higher swelling and solubility values of pinhão starch, in conjunction with the higher storage modulus (G') suggest new different applications of this novel starch. The low protein content of the starch granule favors applications like production of glucose and fructose syrups. The simple method of extraction and the high yield of starch from pinhão seed might be attractive not only for pilot‐plant but also for commercial‐scale production.     

Mass Transfer During Vanilla Pods Solid Liquid Extraction: Effect of Extraction Method

In this paper, experimental kinetics of vanilla pods’ solid–liquid extraction were obtained by three different methods: with agitation, without agitation, and microwave-assisted (MAE) without agitation. The extraction kinetics of aroma compounds (vanillin, p-hydroxybenzaldehyde, and p-hydroxybenzoic acid) was measured in vanilla pods (refined) and extracts by high-performance liquid chromatography. Additionally, the equilibrium distribution of aroma compounds between phases and the retained solution by refined pods were experimentally evaluated. A mechanistic model of two simultaneous algebraic equations was fitted to experimental data in order to estimate the aroma compound diffusivities inside the pods and mass transfer coefficients in the extract. The diffusivities in vanilla pods at 50 °C were 4.31?×?10^?11, 2.93?×?10^?11, and 3.50?×?10^?11?m²?s^?1 for vanillin, p-hydroxybenzaldehyde, and p-hydroxybenzoic acid, respectively. External mass transfer coefficients were in the order of 1.0?×?10^?4?m?s^?1 for forced convection extraction and MAE and 3.33?×?10^?7?m?s^?1 for natural convection extraction.