scholarly journals Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

2014 ◽  
Vol 10 ◽  
pp. 714-721 ◽  
Author(s):  
Yuta Takano ◽  
Yuki Nagashima ◽  
M Ángeles Herranz ◽  
Nazario Martín ◽  
Takeshi Akasaka
Keyword(s):  
Thermal Stability ◽  
Material Science ◽  
Molecular Structures ◽  
Spectroscopic Methods ◽  
Dynamic Nmr ◽  
The Novel ◽  
Endohedral Metallofullerenes ◽  
Derivatives Of ◽  
Paramagnetic Properties

The [4 + 2] cycloaddition of o-quinodimethanes, generated in situ from the sultine 4,5-benzo-3,6-dihydro-1,2-oxathiin 2-oxide and its derivative, to La metal-encapsulated fullerenes, La2@C80 or La@C82, afforded the novel derivatives of endohedral metallofullerenes (3a,b, 4a,b and 5b). Molecular structures of the resulting compounds were elucidated using spectroscopic methods such as MALDI–TOF mass, optical absorption, and NMR spectroscopy. The [4 + 2] adducts of La2@C80 (3a,b, and 4a,b) and La@C82 (5b), respectively, retain diamagnetic and paramagnetic properties, as confirmed by EPR spectroscopy. Dynamic NMR measurements of 4a at various temperatures demonstrated the boat-to-boat inversions of the addend. In addition, 5b revealed remarkable thermal stability in comparison with the reported [4 + 2] cycloadduct of pentamethylcyclopentadiene and La@C82 (6). These findings demonstrate the utility of sultines to afford thermodynamically stable endohedral metallofullerene derivatives for the use in material science.

Ethoxy and silsesquioxane derivatives of antimony as dopant precursors: unravelling the structure and thermal stability of surface species on SiO2

2017 ◽  
Vol 19 (12) ◽  
pp. 8595-8601 ◽  
Author(s):  
T. Alphazan ◽  
P. Florian ◽  
C. Thieuleux
Keyword(s):  
Thermal Stability ◽  
Solid State Nmr ◽  
Surface Species ◽  
Elemental Analyses ◽  
Sb Doping ◽  
Controlled Preparation ◽  
Non Destructive ◽  
Derivatives Of ◽  
Thermal Stability Of

We report here the controlled preparation of SiO2 supported Sb-(mono)layers and their thorough characterization (in situ IR, solid-state NMR, elemental analyses) for the non-destructive Sb-doping of semiconductors.

Synthesis and Characterization of Poly (ε-caprolactone)/ TiO2 Nanocomposites Obtained by In Situ Polymerization

2011 ◽  
Vol 328-330 ◽  
pp. 1533-1536
Author(s):  
Guang Shuo Wang ◽  
Zhi Yong Wei ◽  
Lian Liu ◽  
Pei Wang ◽  
Min Qi
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Crystalline Structure ◽  
Synthesis And Characterization ◽  
The Novel ◽  
Biodegradable Poly ◽  
Thermal Stability Of ◽  
Nucleating Effect

The novel biodegradable poly (ε-caprolactone)/TiO2 nanocomposites were prepared by in situ polymerization of ε-caprolactone in the presence of modified-TiO2 nanoparticles as initiator. The molecular weight of poly (ε-caprolactone) (PCL) matrix was dependent on the amount of the TiO2 fillers. The incorporation of TiO2 did not significantly affect the crystalline structure of PCL. An astounding nucleating effect of TiO2 on PCL crystallization was observed. The enhanced thermal stability of PCL nanocomposites was observed. The novel biodegradable poly (ε-caprolactone)/TiO2 nanocomposites were prepared by in situ polymerization of ε-caprolactone in the presence of modified-TiO2 nanoparticles as initiator. The molecular weight of poly (ε-caprolactone) (PCL) matrix was dependent on the amount of the TiO2 fillers. The incorporation of TiO2 did not significantly affect the crystalline structure of PCL. An astounding nucleating effect of TiO2 on PCL crystallization was observed. The enhanced thermal stability of PCL nanocomposites was observed.

IN SITU SYNTHESIS OF CORAL-LIKE MELAMINE FORMALDEHYDE RESINS/CARBON NANOTUBES MICROPARTICLES

2017 ◽  
Vol 24 (Supp02) ◽  
pp. 1850021
Author(s):  
SHAOYAN MOU ◽  
YONG JIANG
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Stability ◽  
Growth Process ◽  
In Situ Polymerization ◽  
In Situ Synthesis ◽  
Composite Particles ◽  
The Novel ◽  
Melamine Formaldehyde ◽  
Good Thermal Stability

A kind of coral-like melamine formaldehyde resins/carbon nanotubes (MF/CNTs) composite particles were prepared via in situ polymerization, which showed good thermal stability under 450[Formula: see text]C. To illustrate the mechanism of the polymer growth process, silica/CNTs were also prepared via the same method to achieve a contrast. Generally, two models were used to illustrate silica growth mechanism, the monomer addition one and the controlled aggregation one. We preferred that the monomer addition model could explain the growth of the novel coral-like MF/CNTs particles.

Intramolecular Michael-type additions. II. Synthesis of derivatives of 7-thia-2-azabicyclo[3.2.1]oct-3-ene, a novel heterocyclic ring system

1980 ◽  
Vol 58 (8) ◽  
pp. 794-802 ◽  
Author(s):  
Marion E. M Baggs ◽  
Brian Gregory
Keyword(s):  
Sodium Hydroxide ◽  
Ammonium Hydroxide ◽  
Heterocyclic Ring ◽  
Ring System ◽  
Spectroscopic Methods ◽  
The Novel ◽  
Derivatives Of ◽  
By Products

The isothiouronium salt derived from dimethyl 4-chloromethyl-1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate reacted with ammonium hydroxide to give dimethyl 7-thia-2-aza-1,3-dimethylbicyclo[3.2.1]oct-3-ene-4,8-dicarboxylate, which could be converted back to a dihydropyridine using iodomethane. Replacement of ammonium hydroxide by sodium hydroxide afforded a tetrahydro- and a dihydrothieno[3,4-c]pyridine as by-products. 3,5-Diacetyl-4-chloromethyl-1,4-dihydro-2,6-dimethylpyridine reacted with thiourea, followed by ammonium hydroxide, to give 3-acetyl-2-methylpyrrole, 4-acetyl- and 4,8-diacetyl-7-thia-2-aza-1,3-dimethylbicyclo[3.2.1]oct-3-ene. The structure and stereochemistry of the novel 7-thia-2-azabicyclo[3.2.1]octenes are established using spectroscopic methods. The mechanism of their formation is discussed in terms of Baldwin's rules.

Thermal gravimetric analysis of in-situ crosslinked nanocellulose whiskers • poly(methyl vinyl ether-co-maleic acid) • polyethylene glycol

TAPPI Journal ◽  
2011 ◽  
Vol 10 (4) ◽  
pp. 29-33
Author(s):  
LEE A. GOETZ ◽  
AJI P. MATHEW ◽  
KRISTIINA OKSMAN ◽  
ARTHUR J. RAGAUSKAS
Keyword(s):  
Thermal Stability ◽  
Polyethylene Glycol ◽  
Vinyl Ether ◽  
Thermal Gravimetric Analysis ◽  
Maleic Acid ◽  
Gravimetric Analysis ◽  
Thermal Gravimetric ◽  
Methyl Vinyl ◽  
Methyl Vinyl Ether

The thermal stability and decomposition of in-situ crosslinked nanocellulose whiskers – poly(methyl vinyl ether-co-maleic acid) – polyethylene glycol formulations (PMVEMA-PEG), (25%, 50%, and 75% whiskers) – were investigated using thermal gravimetric analysis (TGA) methods. The thermal degradation behavior of the films varied according to the percent cellulose whiskers in each formulation. The presence of cellulose whiskers increased the thermal stability of the PMVEMA-PEG matrix.

scholarly journals Influence of protein (human galectin-3) design on aspects of lectin activity

2020 ◽  
Vol 154 (2) ◽  
pp. 135-153 ◽  
Author(s):  
Gabriel García Caballero ◽  
Donella Beckwith ◽  
Nadezhda V. Shilova ◽  
Adele Gabba ◽  
Tanja J. Kutzner ◽  
...  
Keyword(s):  
Protein Design ◽  
Full Range ◽  
Biological Information ◽  
The Novel ◽  
Modular Assembly ◽  
Binding Partners ◽  
Galectin 3 ◽  
Potential Applications ◽  
Similar Affinity

Abstract The concept of biomedical significance of the functional pairing between tissue lectins and their glycoconjugate counterreceptors has reached the mainstream of research on the flow of biological information. A major challenge now is to identify the principles of structure–activity relationships that underlie specificity of recognition and the ensuing post-binding processes. Toward this end, we focus on a distinct feature on the side of the lectin, i.e. its architecture to present the carbohydrate recognition domain (CRD). Working with a multifunctional human lectin, i.e. galectin-3, as model, its CRD is used in protein engineering to build variants with different modular assembly. Hereby, it becomes possible to compare activity features of the natural design, i.e. CRD attached to an N-terminal tail, with those of homo- and heterodimers and the tail-free protein. Thermodynamics of binding disaccharides proved full activity of all proteins at very similar affinity. The following glycan array testing revealed maintained preferential contact formation with N-acetyllactosamine oligomers and histo-blood group ABH epitopes irrespective of variant design. The study of carbohydrate-inhibitable binding of the test panel disclosed up to qualitative cell-type-dependent differences in sections of fixed murine epididymis and especially jejunum. By probing topological aspects of binding, the susceptibility to inhibition by a tetravalent glycocluster was markedly different for the wild-type vs the homodimeric variant proteins. The results teach the salient lesson that protein design matters: the type of CRD presentation can have a profound bearing on whether basically suited oligosaccharides, which for example tested positively in an array, will become binding partners in situ. When lectin-glycoconjugate aggregates (lattices) are formed, their structural organization will depend on this parameter. Further testing (ga)lectin variants will thus be instrumental (i) to define the full range of impact of altering protein assembly and (ii) to explain why certain types of design have been favored during the course of evolution, besides opening biomedical perspectives for potential applications of the novel galectin forms.

scholarly journals Seawater Absorption and Adhesion Properties of Hydrophobic and Superhydrophobic Thermoset Epoxy Nanocomposite Coatings

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 272
Author(s):  
Ayman M. Atta ◽  
Mohamed H. El-Newehy ◽  
Meera Moydeen Abdulhameed ◽  
Mohamed H. Wahby ◽  
Ahmed I. Hashem
Keyword(s):  
Thermal Stability ◽  
Oleic Acid ◽  
Salt Spray ◽  
Adhesion Properties ◽  
In Situ Modification ◽  
Long Time ◽  
Seawater Environment ◽  
Thermoset Epoxy ◽  
The Cost

The enhancement of both thermal and mechanical properties of epoxy materials using nanomaterials becomes a target in coating of the steel to protect it from aggressive environmental conditions for a long time, with reducing the cost. In this respect, the adhesion properties of the epoxy with the steel surfaces, and its proper superhyrophobicity to repel the seawater humidity, can be optimized via addition of green nanoparticles (NPs). In-situ modification of silver (Ag) and calcium carbonate (CaCO3) NPs with oleic acid (OA) was carried out during the formation of Ag−OA and CaCO3−OA, respectively. The epoxide oleic acid (EOA) was also used as capping for Ca−O3 NPs by in-situ method and epoxidation of Ag−OA NPs, too. The morphology, thermal stability, and the diameters of NPs, as well as their dispersion in organic solvent, were investigated. The effects of the prepared NPs on the exothermic curing of the epoxy resins in the presence of polyamines, flexibility or rigidity of epoxy coatings, wettability, and coatings durability in aggressive seawater environment were studied. The obtained results confirmed that the proper superhyrophobicity, coating adhesion, and thermal stability of the epoxy were improved after exposure to salt spray fog for 2000 h at 36 °C.

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