scholarly journals Effects of Petroleum-Based Oils as Dispersing Aids on Physicochemical Characteristics of Magnetorheological Elastomers

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7026
Author(s):  
Norizatie Muhammad Zaki ◽  
Nurul Azhani Yunus ◽  
Muhamad Shakir Yusoff ◽  
Saiful Amri Mazlan ◽  
Siti Aishah Abdul Aziz ◽  
...  
Keyword(s):  
Magnetic Particles ◽  
Physicochemical Characteristics ◽  
Magnetorheological Elastomers ◽  
Weight Percentage ◽  
Chemical Structures ◽  
Microstructure Observation ◽  
Curing Characteristics ◽  
Similar Chemical ◽  
Low Performance ◽  
Light Mineral

This paper investigated the effects of petroleum-based oils (PBOs) as a dispersing aid on the physicochemical characteristics of natural rubber (NR)-based magnetorheological elastomers (MREs). The addition of PBOs was expected to overcome the low performance of magnetorheological (MR) elastomers due to their inhomogeneous dispersion and the mobility of magnetic particles within the elastomer matrix. The NR-based MREs were firstly fabricated by mixing the NR compounds homogeneously with different ratios of naphthenic oil (NO), light mineral oil (LMO), and paraffin oil (PO) to aromatic oil (AO), with weight percentage ratios of 100:0, 70:30, 50:50, and 30:70, respectively. From the obtained results, the ratios of NO mixed with low amounts of AO improved the material physicochemical characteristics, such as thermal properties. Meanwhile, LMO mixed the AO led to the best results for curing characteristics, microstructure observation, and magnetic properties of the MREs. We found that the LMO mixed with a high content of AO could provide good compatibility between the rubber molecular and magnetic particles due to similar chemical structures, which apparently enhance the physicochemical characteristics of MREs. In conclusion, the 30:70 ratio of LMO:AO is considered the preferable dispersing aid for MREs due to structural compounds present in the oil that enhance the physicochemical characteristics of the NR-based MREs.

scholarly journals Synthesis and Biological Activity of New Brassinosteroid Analogs of Type 24-Nor-5β-Cholane and 23-Benzoate Function in the Side Chain

2021 ◽  
Vol 22 (9) ◽  
pp. 4808
Author(s):  
Nitza Soto ◽  
Karoll Ferrer ◽  
Katy Díaz ◽  
César González ◽  
Lautaro Taborga ◽  
...  
Keyword(s):  
Good Alternative ◽  
Positive Control ◽  
Starting Material ◽  
Chemical Structures ◽  
High Reaction ◽  
Similar Chemical ◽  
Synthetic Procedure ◽  
Hyodeoxycholic Acid ◽  
External Stresses

Brassinosteroids are polyhydroxysteroids that are involved in different plants’ biological functions, such as growth, development and resistance to biotic and external stresses. Because of its low abundance in plants, much effort has been dedicated to the synthesis and characterization of brassinosteroids analogs. Herein, we report the synthesis of brassinosteroid 24-nor-5β-cholane type analogs with 23-benzoate function and 22,23-benzoate groups. The synthesis was accomplished with high reaction yields in a four-step synthesis route and using hyodeoxycholic acid as starting material. All synthesized analogs were tested using the rice lamina inclination test to assess their growth-promoting activity and compare it with those obtained for brassinolide, which was used as a positive control. The results indicate that the diasteroisomeric mixture of monobenzoylated derivatives exhibit the highest activity at the lowest tested concentrations (1 × 10−8 and 1 × 10−7 M), being even more active than brassinolide. Therefore, a simple synthetic procedure with high reaction yields that use a very accessible starting material provides brassinosteroid synthetic analogs with promising effects on plant growth. This exploratory study suggests that brassinosteroid analogs with similar chemical structures could be a good alternative to natural brassinosteroids.

scholarly journals Influencing Factors on the Physicochemical Characteristics of Tea Polysaccharides

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3457
Author(s):  
Ting Hu ◽  
Peng Wu ◽  
Jianfeng Zhan ◽  
Weixin Wang ◽  
Junfeng Shen ◽  
...  
Keyword(s):  
Influencing Factors ◽  
Biological Activities ◽  
Structural Difference ◽  
Physicochemical Characteristics ◽  
Bioactive Constituents ◽  
Preparation Methods ◽  
Processing Technologies ◽  
Chemical Structures ◽  
Tea Polysaccharides ◽  
Fine Structures

Tea polysaccharides (TPSs) are one of the main bioactive constituents of tea with various biological activities such as hypoglycemic effect, antioxidant, antitumor, and immunomodulatory. The bioactivities of TPSs are directly associated with their structures such as chemical composition, molecular weight, glycosidic linkages, and conformation among others. To study the relationship between the structures of TPSs and their bioactivities, it is essential to elucidate the structure of TPSs, particularly the fine structures. Due to the vast variation nature of monosaccharide units and their connections, the structure of TPSs is extremely complex, which is also affected by several major factors including tea species, processing technologies of tea and isolation methods of TPSs. As a result of the complexity, there are few studies on their fine structures and chain conformation. In the present review, we aim to provide a detailed summary of the multiple factors influencing the characteristics of TPS chemical structures such as variations of tea species, degree of fermentation, and preparation methods among others as well as their applications. The main aspects of understanding the structural difference of TPSs and influencing factors are to assist the study of the structure and bioactivity relationship and ultimately, to control the production of the targeted TPSs with the most desired biological activity.

Molecular Motion Analysis of 5CB in PDLCs Using Solid-State 13C NMR Relaxation Spectroscopy

1993 ◽  
Vol 47 (7) ◽  
pp. 933-941 ◽  
Author(s):  
Karen L. Buchert ◽  
Jack L. Koenig ◽  
Shi-Qing Wang ◽  
John L. West
Keyword(s):  
Liquid Crystal ◽  
Solid State ◽  
Polymer Matrix ◽  
Nmr Relaxation ◽  
Domain Size ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Polymer Dispersed ◽  
Submicron Droplets ◽  
Significant Change

In samples of polymer-dispersed liquid crystals (PDLCs), submicron droplets of liquid crystal reside within a polymer matrix. By the use of the cross polarization technique for solid-state 13C NMR spectroscopy, the NMR spectrum of the liquid crystal can be obtained without interference from the polymer spectrum, even though the two materials have some similar chemical structures. Both 13C T1 and 13C T1 ρ relaxation experiments were performed on a PDLC system of 5CB in epoxy as a function of 5CB domain size. The 13C T1 relaxation constants and the localized motions they measure showed no significant change over the liquid crystal domain size studied. However, the 13C T1 ρ relaxation constants and the segmental motions of molecules they measure revealed a significant change over the liquid crystal domain size studied. Therefore, the 13C T1 ρ values can be used to determine the change in mobility of the molecular segments of the SCB molecules resulting from increased interaction between the liquid crystal and the polymer matrix and to further understand the importance of the molecular motions of the liquid crystal in the switching phenomenon for PDLC materials.

scholarly journals Competitive cocrystallization and its application in the separation of flavonoids

IUCrJ ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 195-207
Author(s):  
Yanming Xia ◽  
Yuanfeng Wei ◽  
Hui Chen ◽  
Shuai Qian ◽  
Jianjun Zhang ◽  
...  
Keyword(s):  
Free Energy ◽  
Formation Constant ◽  
Energy Gap ◽  
Hirshfeld Surface ◽  
Methanol Solution ◽  
Model Compounds ◽  
Electronic Density ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Interaction Contribution

Recently, cocrystallization has been widely employed to tailor physicochemical properties of drugs in the pharmaceutical field. In this study, cocrystallization was applied to separate natural compounds with similar structures. Three flavonoids [baicalein (BAI), quercetin (QUE) and myricetin (MYR)] were used as model compounds. The coformer caffeine (CAF) could form cocrystals with all three flavonoids, namely BAI–CAF (cocrystal 1), QUE–CAF (cocrystal 2) and MYR–CAF (cocrystal 3). After adding CAF to methanol solution containing MYR and QUE (or QUE and BAI), cocrystal 3 (or cocrystal 2) preferentially formed rather than cocrystal 2 (or cocrystal 1), indicating that flavonoid separation could be achieved by competitive cocrystallization. After co-mixing the slurry of two flavonoids with CAF followed by centrifugation, the resolution ratio that could be achieved was 70–80% with purity >90%. Among the three cocrystals, cocrystal 3 showed the lowest formation constant with a negative Gibbs free energy of nucleation and the highest energy gap. Hirshfeld surface analysis and density of states analysis found that cocrystal 3 had the highest strong interaction contribution and the closest electronic density, respectively, followed by cocrystal 2 and cocrystal 1, suggesting CAF could competitively form a cocrystal with MYR much more easily than QUE and BAI. Cocrystallization is a promising approach for green and effective separation of natural products with similar chemical structures.

scholarly journals Dinucleoside polyphosphates act as 5’-RNA caps in Escherichia coli

2019 ◽  
Author(s):  
Oldřich Hudeček ◽  
Roberto Benoni ◽  
Martin Culka ◽  
Martin Hubálek ◽  
Lubomír Rulíšek ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Rna Stability ◽  
E Coli ◽  
Chemical Structures ◽  
Additional Layer ◽  
Similar Chemical ◽  
Decapping Enzyme ◽  
Almost All ◽  
Dinucleoside Polyphosphates ◽  
Rna Caps

Dinucleoside polyphosphates (NpnNs), discovered more than 50 years ago,1 are pleiotropic molecules present in almost all types of cells.2 It has been shown that their intracellular concentration can under stress conditions increase from the µM to mM range 2,3. However, the cellular roles and mechanisms of action of NpnNs are still speculative4,5. They have never been considered as part of the RNA, even though they have similar chemical structures as already known RNA caps, such as the nicotinamide adenine dinucleotide (NAD)6-8 and 7-methylguanylate cap9. Here, we show that both methylated and non-methylated Npn Ns serve as RNA caps in Escherichia coli (E. coli). NpnNs are excellent substrates for T7 and E. coli RNA polymerases (RNAP) and efficiently initiate transcription. Further, we demonstrate that the E. coli decapping enzyme RNA 5’ pyrophosphohydrolase (RppH) is able to remove the NpnNs-cap from the RNA. RppH was, however, not able to cleave the methylated forms of the NpnN-caps, suggesting that the methylation adds an additional layer to the RNA stability regulation. Our work introduces an original perspective on the chemical structure of RNA in prokaryotes and the function of RNA caps. This is the first evidence that small molecules like NpnNs can act in cells via their incorporation into RNA and influence the cellular metabolism.

scholarly journals Modified Epoxy with Chitosan Triazine Dihydrazide Derivatives for Mechanical and Corrosion Protection of Steel

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1256
Author(s):  
Ayman M. Atta ◽  
Ayman El-Faham ◽  
Hamad A. Al-Lohedan ◽  
Abdelrahman O. Ezzat
Keyword(s):  
Exothermic Reaction ◽  
Epoxy Coatings ◽  
Thermal Stabilities ◽  
Chemical Structures ◽  
Curing Characteristics ◽  
Mechanical Adhesion ◽  
Molecular Masses ◽  
Amine Groups ◽  
Surface Morphologies ◽  
Modified Epoxy

Modification of the curing exothermic reaction of epoxy resin with polyamine (PA) hardeners by new chemically bonded fillers to improve the mechanical properties and anticorrosion performances of the epoxy coatings is the main goal for wide applications of epoxy coatings. In this work, the chemical structure of chitosan was modified with triazine hydrazide moiety that contains primary, secondary, and tertiary amine groups to act as activator and dangling chain linkers during the curing of epoxy/PA system. Different molecular masses of chitosan were modified with triazine dihydrazide moiety (Ch-TH2), and their chemical structures and surface morphologies were identified. Their thermal stabilities were investigated, and the grafting percentages with triazine hydrazide were determined from thermal analysis. Different weight percentages of Ch-TH2 ranged from 1 to 10 Wt. % were added to the epoxy/PA system, and their curing characteristics, such as heat enthalpy and glass transition temperature, were determined from non-isothermal dynamic scanning calorimetric thermograms. The effects of molecular masses, triazine dihydrazide %, and Ch-TH2 Wt. % on the mechanical, adhesion and anticorrosive properties of the cured epoxy/PA coatings for steel were investigated. The optimum Ch-TH2 Wt. % was selected from 3 to 6 Wt. % to improve the mechanical, adhesion, and anticorrosive properties of the cured epoxy/PA coatings.

scholarly journals Similar chemical structures, dissimilar triplet quantum yields: a CASPT2 model rationalizing the trend of triplet quantum yields in nitroaromatic systems

2019 ◽  
Vol 21 (20) ◽  
pp. 10514-10522 ◽  
Author(s):  
Angelo Giussani ◽  
Graham A. Worth
Keyword(s):  
Quantum Yields ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Triplet Quantum Yields

S1/S0 accessibility strongly influences the triplet quantum yields of nitronaphthalenes.

MONITORING INTERPARTICLE DISTANCE IN MAGNETORHEOLOGICAL COMPOSITES

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4868-4874
Author(s):  
G. BOSSIS ◽  
E. COQUELLE ◽  
C. NOEL ◽  
F. GIULIERI ◽  
A. M. CHAZE
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
Energy Dissipation ◽  
Viscoelastic Properties ◽  
Magnetic Particles ◽  
Interparticle Distance ◽  
Magnetorheological Elastomer ◽  
Magnetorheological Elastomers ◽  
Magnetic Spheres ◽  
The Creation

We describe two different systems, the first one based on a magnetorheological elastomer and the second one on magnetic particles inside a liquid crystal. In both system we manage to have chain structures with particles that are not in contact. The effect of the gap between particles on the viscoelastic properties are studied. We show in particular how in magnetorheological elastomers, the energy dissipation is closely related to the creation and the motion of cavities in the gap between the particles. In liquid crystal chaining of particles can occur without applying a magnetic field. This happens if the anchoring of liquid crystal on the surface of the particles is homeotropic. We demonstrate how the combination of elastic defects and of a magnetic field allow to obtain microscopic springs made of a pair of magnetic spheres.

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