scholarly journals Aminomethylated Calix[4]resorcinarenes as Modifying Agents for Glycidyl Methacrylate (GMA) Rigid Copolymers Surface

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1147 ◽  
Author(s):  
Betty Astrid Velásquez-Silva ◽  
Alver Castillo-Aguirre ◽  
Zuly Jenny Rivera-Monroy ◽  
Mauricio Maldonado
Keyword(s):  
Elemental Analysis ◽  
Glycidyl Methacrylate ◽  
High Performance ◽  
Epoxy Group ◽  
Hydroxyl Group ◽  
Basic Medium ◽  
Reaction Products ◽  
Experimental Conditions ◽  
Microscopy Imaging ◽  
Ft Ir

Functionalization of tetrapropylcalix[4]resorcinarene, tetrapentylcalix[4]resorcinarene, tetranonylcalix[4]resorcinarene, and tetra-(4-hydroxyphenyl)calix[4]resorcinarene by means of aminomethylation reactions with the amino acids β-alanine and l-proline in the presence of aqueous formaldehyde was carried out. When β-alanine was used, the reaction products were tetrabenzoxazines. The reaction with tetra-(4-hydroxyphenyl)calix[4]resorcinarene did not proceed under the experimental conditions; therefore, l-proline was used, and the corresponding tetra-Mannich base was regio- and diasteroselectively formed. The products were characterized via FT-IR, 1H NMR, 13C NMR, and elemental analysis. With these aminomethylated-calix[4]resorcinarenes, the chemical surface modification of the copolymers poly(GMA–co–EDMA) and poly(BMA–co–EDMA–co–MMA) in a basic medium was studied. The results were quite satisfactory, obtaining the corresponding copolymers functionalized by nucleophilic substitution reaction and ring-opening between the carboxyl group of the upper rim of aliphatic calix[4]resorcinarenes and the hydroxyl group of the lower rim in the aromatic calix[4]resorcinarene and the epoxy group of the glycidyl methacrylate residue of each copolymer. The modified copolymers were characterized via FT-IR, scanning electron microscopy imaging, and elemental analysis. Finally, the modified copolymer surfaces exhibited interaction with peptides, showing their potential application in chromatographic separation techniques such as high-performance liquid chromatography.

scholarly journals Kinetics and Mechanism of Oxidation of Metformin Hydrochloride by Hexamolybdocobaltate(III) in Acidic Medium

2020 ◽  
Vol 33 (1) ◽  
pp. 15-20
Author(s):  
J.D. SAWANT ◽  
K.K. PATIL ◽  
G.S. GOKAVI
Keyword(s):  
Free Radical ◽  
Ir Spectra ◽  
Oxidation Product ◽  
Acidic Medium ◽  
High Performance ◽  
Direct Electron Transfer ◽  
Metformin Hydrochloride ◽  
Experimental Conditions ◽  
Rate Of Reaction ◽  
Ft Ir

The oxidation of metformin hydrochloride by Anderson-Evans type hexamolybdocobaltate(III) anion was investigated under pseudofirst- order condition in acidic medium at 298 K. The rate of reaction is accelerated by increase in the concentration of H+ ion. The decrease in the reaction rate with increase in the concentration of the oxidant [H6CoMo6O24]3- anion and added molybdate ion kinetically indicate existence of the prior equilibria between various forms of the oxidant. In present study, the oxidant exists in monomers [H6CoMo6O24]3- anion, [H5CoMo5O20]2- anion and dimer [H4Co2Mo10O38]6- forms between the pH 2 and 1. The active oxidant species is [H5CoMo5O20]2- anion. Under experimental conditions, the reaction involves direct electron-transfer from metformin center to oxidant anion generating free radical in rate determining step. The fast hydrolysis of formed free radical in presence of second oxidant molecule leads to formation of carbonyl imino functional group in the oxidation product. The ionic strength and solvent polarity had no significant effect on the rate of reaction. FT-IR spectra of metformin and its oxidation product sample were recorded and analyzed. The FT-IR spectra show the change in frequency of the functional groups of oxidation product than that of the pure MET. The formation of oxidation product was confirmed by high performance liquid chromatography associated with electron impact mass spectroscopy (LC/EI-MS). Thermodynamic parameters are evaluated by temperature variation kinetic data and are in support of the proposed mechanism. The probable mechanism is proposed leading to complicated rate law as a result of involvement of prior equillibria between various forms of the oxidant.

scholarly journals Preparation of Methacrylate-based Polymers Modified with Chiral Resorcinarenes and Their Evaluation as Sorbents in Norepinephrine Microextraction

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1428 ◽  
Author(s):  
Castillo-Aguirre ◽  
Maldonado
Keyword(s):  
Chemical Modification ◽  
Rotating Disk ◽  
Mannich Bases ◽  
Experimental Conditions ◽  
Microscopy Imaging ◽  
Modified Polymer ◽  
Modified Polymers ◽  
Composition And Structure ◽  
Artificial Urine ◽  
Ft Ir

Aminomethylation reactions between chiral amino compounds (S)-(-)-1-phenylethylamine and l-proline with tetranonylresorcinarene and tetra-(4-hydroxyphenyl)resorcinarene in presence of formaldehyde were studied. The reaction between l-proline and resorcinarenes generated regioselectively chiral tetra-Mannich bases, due to the molecular incorporation of the fragment of the chiral amino acid. On the other hand, tetranonylresorcinarene and (S)-(-)-1-phenylethylamine formed regio- and diasteroselectively chiral tetrabenzoxazines, both by chiral auxiliary functionalization and by the transformation of the molecular structure that confers inherent chirality. The products obtained were characterized using IR, 1H-NMR, 13C-NMR, COSY, HMQC, and HMBC techniques. The reaction of (S)-(-)-1-phenylethylamine with tetra-(4-hydroxyphenyl)resorcinarene did not proceed under the experimental conditions. Once the chiral aminomethylated tetra-(4-hydroxyphenyl)resorcinarene was obtained, the chemical modification of poly(GMA–co–EDMA) was studied, and the results showed an efficient incorporation of the aminomethylated compound. For the physical modification, chiral aminomethylated tetranonylresorcinarenes were employed, finding that the incorporation of modified resorcinarenes occurs, but with less efficiency than that observed using chemical modification. The modified polymers were characterized via FT-IR, scanning electron microscopy imaging, and elemental analysis. Finally, polymers modified with chiral resorcinarenes were used as sorbents in norepinephrine microextraction; for practical purposes, artificial urine was prepared and used. To perform the microextraction, the decision was made to use the modern rotating-disk sorptive extraction technique (RDSE), because of its analytical attributes as a green, or eco-friendly, technique. According to the results, the method preliminarily validated for the determination of norepinephrine in artificial urine shows that the modified polymer with chiral derivative of tetra-(4-hydroxyphenyl)resorcinarene worked effectively as a new sorbent phase for the quantitative microextraction of norepinephrine, exhibiting high stability and homogeneity of composition and structure within the working range.

Synthesis and Spectral Characterization of New S-Alkylated 1,2,4-Triazoles as Potential Biological Agents

2017 ◽  
Vol 68 (10) ◽  
pp. 2436-2439
Author(s):  
Stefania Felicia Barbuceanu ◽  
Laura Ileana Socea ◽  
Constantin Draghici ◽  
Elena Mihaela Pahontu ◽  
Theodora Venera Apostol ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Spectral Data ◽  
1H Nmr ◽  
Elemental Analysis ◽  
13C Nmr ◽  
Ethyl Bromide ◽  
Spectral Characterization ◽  
Basic Medium ◽  
Phenacyl Bromide

In the work we presented the behavior of 5-(4-(4-X-phenylsulfonyl)phenyl)-4-(n-propyl)-2H-1,2,4-triazole-3(4H)-thiones (X= Cl or Br) with some alkylation agents. Thus, new S-alkylated 1,2,4-triazole derivatives were synthesized by reaction of the corresponding 1,2,4-triazole-3-thione derivatives with different �-halogenated compounds (ethyl bromide, ethyl chloroacetate or phenacyl bromide), in basic medium. The structures of synthesized compounds were elucidated by spectral data (1H-NMR, 13C-NMR, mass spectrometry) and elemental analysis.

Micro-Thermal Field-Flow Fractionation

2002 ◽  
Vol 67 (11) ◽  
pp. 1596-1608 ◽  
Author(s):  
Josef Janča
Keyword(s):  
High Performance ◽  
Thermal Field ◽  
Temperature Drop ◽  
Point Of View ◽  
Constant Field ◽  
Field Flow Fractionation ◽  
Operational Mode ◽  
Experimental Conditions ◽  
Standard Size ◽  
Flow Fractionation

The effect of miniaturization of the separation channel on the performance of thermal field-flow fractionation (TFFF) is substantiated theoretically. The experiments carried out under carefully chosen experimental conditions proved the high performance of the separation of polymers within an extended range of molar masses from relatively low up to ultrahigh-molar-mass (UHMM) samples. The new micro-TFFF allows to achieve high resolution when applying constant field force operation, it makes easy the programming of the temperature drop which is an advantageous operational mode from the point of view of the time of analysis, and it extends considerably the range of perfectly controlled temperature of the cold wall due to a substantial decrease in the heat energy flux compared with standard size channels.

scholarly journals Enhancement of Chloroprene/Natural/Butadiene Rubber Nanocomposite Properties Using Organoclays and Their Combination with Carbon Black as Fillers

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1085
Author(s):  
Patricia Castaño-Rivera ◽  
Isabel Calle-Holguín ◽  
Johanna Castaño ◽  
Gustavo Cabrera-Barjas ◽  
Karen Galvez-Garrido ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Black ◽  
High Performance ◽  
Rubber Matrix ◽  
Butadiene Rubber ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rubber Blends ◽  
Ft Ir ◽  
Chloroprene Rubber

Organoclay nanoparticles (Cloisite® C10A, Cloisite® C15) and their combination with carbon black (N330) were studied as fillers in chloroprene/natural/butadiene rubber blends to prepare nanocomposites. The effect of filler type and load on the physical mechanical properties of nanocomposites was determined and correlated with its structure, compatibility and cure properties using Fourier Transformed Infrared (FT-IR), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and rheometric analysis. Physical mechanical properties were improved by organoclays at 5–7 phr. Nanocomposites with organoclays exhibited a remarkable increase up to 46% in abrasion resistance. The improvement in properties was attributed to good organoclay dispersion in the rubber matrix and to the compatibility between them and the chloroprene rubber. Carbon black at a 40 phr load was not the optimal concentration to interact with organoclays. The present study confirmed that organoclays can be a reinforcing filler for high performance applications in rubber nanocomposites.

Synthesis and Characterization of Reduced Graphene Oxide

2013 ◽  
Vol 678 ◽  
pp. 56-60 ◽  
Author(s):  
Cherukutty Ramakrishnan Minitha ◽  
Ramasamy Thangavelu Rajendrakumar
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Graphite Oxide ◽  
High Performance ◽  
Structural Changes ◽  
Epoxy Group ◽  
Xrd Analysis ◽  
Si Substrates ◽  
Reduced Graphene ◽  
Reduced Graphite Oxide

Reduced graphene oxide is an excellent candidate for various electronic devices such as high performance gas sensors. In this work Graphene oxide was prepared by oxidizing graphite to form graphite oxide. From XRD analysis the peak around 11.5o confirmed that the oxygen was intercalated into graphite. By using hydrazine hydrate, the epoxy group in graphite oxide was reduced then the solution of reduced graphite oxide (rGO) is exfoliated. Raman spectrum of rGO contains both G band (1580 cm-1), D band (1350 cm-1). The remarkable structural changes reveals that reduction of graphene oxide from the values of ID/IG ratio that increase from 0.727 (GO) to 1.414 (rGO). The exfoliated reduced graphite oxide solution is spin coated on to the SiO2/Si substrates.

scholarly journals How Relevant Is It to Use Mineral Proxies to Mimic the Atmospheric Reactivity of Natural Dust Samples? A Reactivity Study Using SO2 as Probe Molecule

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 282
Author(s):  
Darya Urupina ◽  
Manolis N. Romanias ◽  
Frederic Thevenet
Keyword(s):  
High Performance ◽  
Real Life ◽  
Complex Mixtures ◽  
Experimental Conditions ◽  
The Real ◽  
Atmospheric Processes ◽  
Real Effects ◽  
Mineral Aerosols ◽  
Life Impact ◽  
Reactivity Study

The experimental investigation of heterogeneous atmospheric processes involving mineral aerosols is extensively performed in the literature using proxy materials. In this work we questioned the validity of using proxies such as Fe2O3, FeOOH, Al2O3, MgO, CaO, TiO2, MnO2, SiO2, and CaCO3 to represent the behavior of complex mixtures of minerals, such as natural desert and volcanic dusts. Five volcanic dusts and three desert dusts were compared to a number of metal oxides, commonly used in the literature to mimic the behavior of desert dusts in the ability to form sulfites and sulfates on the surface exposed to SO2 gas. First, all samples were aged at room temperature, atmospheric pressure, under controlled experimental conditions of 175 ppm SO2 for 1 h under 30% of relative humidity. Second, they were extracted with 1% formalin and analyzed by High-Performance Liquid Chromatography (HPLC) to quantify and compare the amount of sulfites and sulfates formed on their surfaces. It was evidenced that under the experimental conditions of this study neither one selected pure oxide nor a mixture of oxides can adequately typify the behavior of complex mixtures of natural minerals. Therefore, to evaluate the real-life impact of natural dust on atmospheric processes it is of vital importance to work directly with the natural samples, both to observe the real effects of desert and volcanic dusts and to evaluate the relevancy of proposed proxies.

scholarly journals Biofoam of Spittlebug, Poophilus costalis (Walker): Preferential Sites, Temperature Regulation, Chemical Composition and Antimicrobial Activity

Insects ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 340
Author(s):  
Kitherian Sahayaraj ◽  
Balakrishnan Saranya ◽  
Samy Sayed ◽  
Loko Yêyinou Laura Estelle ◽  
Koilraj Madasamy
Keyword(s):  
Antimicrobial Activity ◽  
Chemical Composition ◽  
High Performance ◽  
Host Plants ◽  
Ground Level ◽  
College Campus ◽  
The Other ◽  
Mimosa Pudica ◽  
Ft Ir ◽  
Gas Chromatography Mass Spectroscopy

The foam produced by nymphs of Poophilus costalis on eleven different host plants belonging to eight families on St. Xavier’s College campus in India was studied over five months. The chemical composition and antimicrobial activity of these biofoams were investigated. The results revealed that P. costalis preferred Theporsia purpurea and Mimosa pudica for laying their eggs and producing foam, over the other tested plants. P. costalis produce their foam on either nodes or internodes on monocotyledons (30%) (p < 0.05), whereas on dicotyledons, they produce more foam on the stems (63.8%) than on the leaves (6.2%) (p < 0.01). The number of nymphs in each piece of foam from P. costalis varied from 1 to 3 (mean = 1.8 per plant). They produced their foam (5.7 to 45.2 cm) from the ground level on a plant. The length and breadth of a piece of foam ranged from 1.0 to 3.9 cm and 0.6 to 4.7 cm, respectively. The foam tended to be cooler than the environment. Qualitative profiling showed that the foam consists of carbohydrates, including maltose; trypsin; amino acids; protease. The foam was also analyzed using a spectrophotometer, Fourier transform infrared spectroscopy (FT-IR), gas chromatography–mass spectroscopy (GC-MS), and high-performance liquid chromatography (HPLC). The antimicrobial activity of the biofoam was the greatest against Staphylococcus aureus, the growth of which was reduced by 55.9 ± 3.9%, suggesting that the foam could be used as an antimicrobial product. However, no activities were observed against Fusarium oxysporum and Candida albicans.

scholarly journals Fast Preparation of High-Performance Wood Materials Assisted by Ultrasonic and Vacuum Impregnation

Forests ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 567
Author(s):  
Hong Yang ◽  
Mingyu Gao ◽  
Jinxin Wang ◽  
Hongbo Mu ◽  
Dawei Qi
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Mechanical Tests ◽  
Vacuum Impregnation ◽  
Natural Forests ◽  
Ultrasonic Pretreatment ◽  
Fast Growing ◽  
Before And After ◽  
New Material ◽  
Ft Ir

In the absence of high-quality hardwood timber resources, we have gradually turned our attention from natural forests to planted fast-growing forests. However, fast-growing tree timber in general has defects such as low wood density, loose texture, and poor mechanical properties. Therefore, improving the performance of wood through efficient and rapid technological processes and increasing the utilization of inferior wood is a good way to extend the use of wood. Densification of wood increases the strength of low-density wood and extends the range of applications for wood and wood-derived products. In this paper, the effects of ultrasonic and vacuum pretreatment on the properties of high-performance wood were explored by combining sonication, vacuum impregnation, chemical softening, and thermomechanical treatments to densify the wood; then, the changes in the chemical composition, microstructure, and mechanical properties of poplar wood before and after treatment were analyzed comparatively by FT-IR, XRD, SEM, and mechanical tests. The results showed that with ultrasonic pretreatment and vacuum impregnation, the compression ratio of high-performance wood reached its highest level and the MOR and MOE reached their maximums. With the help of this method, fast-growing softwoods can be easily prepared into dense wood materials, and it is hoped that this new material can be applied in the fields of construction, aviation, and automobile manufacturing.

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