Synthesis and properties of pyrazine-based oligomeric phthalonitrile resins

2019 ◽  
Vol 31 (9-10) ◽  
pp. 1075-1084 ◽  
Author(s):  
Yao Liu ◽  
Puguang Ji ◽  
Zhenjiang Zhang ◽  
Xiaoyan Yu ◽  
Kimiyoshi Naito ◽  
...  
Keyword(s):  
Complex Viscosity ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
One Pot ◽  
X Ray ◽  
Tetragonal System ◽  
End Capping ◽  
Initial Storage ◽  
Reaction Activation Energy

The pyrazine-based oligomeric phthalonitrile (PN) monomer, 2,6-bis[3-(3,4-dicyanophenoxy)phenoxy]pyrazine (BCPP), was synthesized from the reaction of an excess amount of resorcinol with 2,6-dichloropyrazine in the presence of potassium carbonate, followed by end-capping with 4-nitrophthalonitrile in a two-step, one-pot reaction. 4-(Aminophenoxy)phthalonitrile was applied to promote the curing reaction. The curing behavior was investigated by differential scanning calorimetry and rheological behavior, showing a wide processing window of 94°C, a complex viscosity of less than 1.5 Pa·s and a lower reaction activation energy of 32.57 kJ mol−1. The structure of the BCPP monomer was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The unit cell was determined to be tetragonal system by wide-angle X-ray diffraction. The monomer was cured to yield cross-linked polymers, which exhibited a high initial storage modulus, excellent glass transition temperature, outstanding thermal stability, and low water uptake.

scholarly journals Non-Isothermal Crystallization Behavior of PEEK/Graphene Nanoplatelets Composites from Melt and Glass States

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 124 ◽  
Author(s):  
Ángel Alvaredo ◽  
María Martín ◽  
Pere Castell ◽  
Roberto Guzmán de Villoria ◽  
Juan Fernández-Blázquez
Keyword(s):  
Real Time ◽  
Orthorhombic Phase ◽  
Complex Viscosity ◽  
Crystallization Time ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Chain Mobility ◽  
Peek Composite ◽  
Poly Ether Ether Ketone

The effect of the graphene nanoplateletets (GNP), at concentration of 1, 5 and 10 wt %, in Poly ether ether ketone (PEEK) composite crystallization from melt and during cold crystallization were investigated by differential scanning calorimetry (DSC) and real time X-ray diffraction experiments. DSC results revealed a double effect of GNP: (a) nucleating effect crystallization from melt started at higher temperatures and (b) longer global crystallization time due to the restriction in the polymer chain mobility. This hindered mobility were proved by rheological behavior of nanocomposites, because to the increase of complex viscosity, G′, G″ with the GNP content, as well as the non-Newtonian behavior found in composites with high GNP content. Finally, real time wide and small angle synchrotron X-ray radiation (WAXS/SAXS) X-ray measurements showed that GNP has not affected the orthorhombic phase of PEEK nor the evolution of the crystal phase during the crystallization processes. However, the correlation length of the crystal obtained by WAXS and the long period (L) by SAXS varied depending on the GNP content.

scholarly journals Green process for green materials: viable low-temperature lipase-catalysed synthesis of renewable telechelics in supercritical CO 2

2015 ◽  
Vol 373 (2057) ◽  
pp. 20150073 ◽  
Author(s):  
S. Curia ◽  
A. F. Barclay ◽  
S. Torron ◽  
M. Johansson ◽  
S. M. Howdle
Keyword(s):  
Reaction Medium ◽  
Gel Permeation Chromatography ◽  
Side Reactions ◽  
Resonance Spectroscopy ◽  
Scanning Calorimetry ◽  
One Pot ◽  
Free System ◽  
Flight Mass Spectrometry ◽  
Green Materials ◽  
End Capping

We present a novel near-ambient-temperature approach to telechelic renewable polyesters by exploiting the unique properties of supercritical CO 2 (scCO 2 ). Bio-based commercially available monomers have been polymerized and functional telechelic materials with targeted molecular weight prepared by end-capping the chains with molecules containing reactive moieties in a one-pot reaction. The use of scCO 2 as a reaction medium facilitates the effective use of Candida antarctica Lipase B (CaLB) as a catalyst at a temperature as low as 35°C, hence avoiding side reactions, maintaining the end-capper functionality and preserving the enzyme activity. The functionalized polymer products have been characterized by 1 H nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry, gel permeation chromatography and differential scanning calorimetry in order to carefully assess their structural and thermal properties. We demonstrate that telechelic materials can be produced enzymatically at mild temperatures, in a solvent-free system and using renewably sourced monomers without pre-modification, by exploiting the unique properties of scCO 2 . The macromolecules we prepare are ideal green precursors that can be further reacted to prepare useful bio-derived films and coatings.

scholarly journals Novel Quaternary Ammonium Derivatives of 4-Pyrrolidino Pyridine: Synthesis, Structural, Thermal, and Antibacterial Studies

Crystals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 339 ◽  
Author(s):  
Rusi Rusew ◽  
Vanya Kurteva ◽  
Boris Shivachev
Keyword(s):  
Crystal Structures ◽  
Quaternary Ammonium ◽  
Antibacterial Properties ◽  
Bacterial Strains ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Orthorhombic Crystal ◽  
One Pot ◽  
X Ray ◽  
Derivatives Of

Six novel quaternary ammonium derivatives of 4-pyrrolidino pyridine were prepared and isolated via a facile one-pot synthesis and a simple purification procedure. The purity and the molecular structure of the 4-pyrrolidino pyridine derivatives were confirmed with 1H and 13C NMR spectroscopy and powder X-ray diffraction techniques. The crystal structures of the compounds were characterized by single crystal X-ray diffraction (SCXRD) and their thermal properties were studied by Differential Scanning Calorimetry (DSC) analyses. The antibacterial properties of the title compounds against five bacterial strains were evaluated using Kirby–Bauer disk diffusion susceptibility test. The compounds crystallize in the monoclinic or orthorhombic crystal systems (space groups: P21/c, P21/n, or P212121) and their crystal structures are stabilized by a combination of intra- and intermolecular halogen bonding interactions, short contacts and π-π interactions. Above interactions, they contribute to the thermal stability and lack of phase transition effects up to 350 °C. Two of the compounds possess antibacterial effect against E. coli or S. aureus bacterial strains—similar or better than the kanamycin reference.

scholarly journals Pharmaceutical Hydrates Analysis—Overview of Methods and Recent Advances

Pharmaceutics ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 959
Author(s):  
Ewa Jurczak ◽  
Anna Helena Mazurek ◽  
Łukasz Szeleszczuk ◽  
Dariusz Maciej Pisklak ◽  
Monika Zielińska-Pisklak
Keyword(s):  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Hydration Kinetics ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Degree Of Hydration ◽  
Pharmaceutical Ingredients ◽  
Fourier Transformed Infrared Spectroscopy ◽  
Ft Ir ◽  
Analytical Approaches

This review discusses a set of instrumental and computational methods that are used to characterize hydrated forms of APIs (active pharmaceutical ingredients). The focus has been put on highlighting advantages as well as on presenting some limitations of the selected analytical approaches. This has been performed in order to facilitate the choice of an appropriate method depending on the type of the structural feature that is to be analyzed, that is, degree of hydration, crystal structure and dynamics, and (de)hydration kinetics. The presented techniques include X-ray diffraction (single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD)), spectroscopic (solid state nuclear magnetic resonance spectroscopy (ssNMR), Fourier-transformed infrared spectroscopy (FT-IR), Raman spectroscopy), thermal (differential scanning calorimetry (DSC), thermogravimetric analysis (TGA)), gravimetric (dynamic vapour sorption (DVS)), and computational (molecular mechanics (MM), Quantum Mechanics (QM), molecular dynamics (MD)) methods. Further, the successful applications of the presented methods in the studies of hydrated APIs as well as studies on the excipients’ influence on these processes have been described in many examples.

Studies on the Preparation, Characterization and Solubility of -Cyclodextrin-Roxythromycin Inclusion Complexes

2009 ◽  
Vol 2 (2) ◽  
pp. 523-530
Author(s):  
D. Nagasamy Venkatesh ◽  
S. Karthick ◽  
M. Umesh ◽  
G. Vivek ◽  
R.M. Valliappan ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Inclusion Complexes ◽  
Phase Solubility ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Ir Studies ◽  
Poorly Soluble ◽  
Poorly Soluble Drug

Roxythromycin/ β-cyclodextrin (Roxy/ β-CD) dispersions were prepared with a view to study the influence of β-CD on the solubility and dissolution rate of this poorly soluble drug. Phase-solubility profile indicated that the solubility of roxythromycin was significantly increased in the presence of β-cyclodextrin and was classified as AL-type, indicating the 1:1 stoichiometric inclusion complexes. Physical characterization of the prepared systems was carried out by differential scanning calorimetry (DSC), X-ray diffraction studies (XRD) and IR studies. Solid state characterization of the drug β-CD binary system using XRD, FTIR and DSC revealed distinct loss of drug crystallinity in the formulation, ostensibly accounting for enhancement of dissolution rate.

scholarly journals A review of nanotechnology with an emphasis on Nanoplex

2015 ◽  
Vol 51 (2) ◽  
pp. 255-263
Author(s):  
Rupali Nanasaheb Kadam ◽  
Raosaheb Sopanrao Shendge ◽  
Vishal Vijay Pande
Keyword(s):  
Drug Delivery ◽  
Drug Delivery Systems ◽  
Drug Loading ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Conventional Drug ◽  
Anionic Drugs ◽  
Oppositely Charged ◽  
The Brain

<p>The use of nanotechnology based on the development and fabrication of nanostructures is one approach that has been employed to overcome the challenges involved with conventional drug delivery systems. Formulating Nanoplex is the new trend in nanotechnology. A nanoplex is a complex formed by a drug nanoparticle with an oppositely charged polyelectrolyte. Both cationic and anionic drugs form complexes with oppositely charged polyelectrolytes. Compared with other nanostructures, the yield of Nanoplex is greater and the complexation efficiency is better. Nanoplex are also easier to prepare. Nanoplex formulation is characterized through the production yield, complexation efficiency, drug loading, particle size and zeta potential using scanning electron microscopy, differential scanning calorimetry, X-ray diffraction and dialysis studies. Nanoplex have wide-ranging applications in different fields such as cancer therapy, gene drug delivery, drug delivery to the brain and protein and peptide drug delivery.</p>

scholarly journals Synthesis and Characterization of N-Substituted Polyether-Block-Amide Copolymers

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 773
Author(s):  
Jyun-Yan Ye ◽  
Kuo-Fu Peng ◽  
Yu-Ning Zhang ◽  
Szu-Yuan Huang ◽  
Mong Liang
Keyword(s):  
Titanium Isopropoxide ◽  
Decomposition Temperature ◽  
Phenyl Isocyanate ◽  
Cross Linking ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Degradation Temperature ◽  
Melt Polycondensation ◽  
Structural Regularity

A series of N-substituted polyether-block-amide (PEBA-X%) copolymers were prepared by melt polycondensation of nylon-6 prepolymer and polytetramethylene ether glycol at an elevated temperature using titanium isopropoxide as a catalyst. The structure, thermal properties, and crystallinity of PEBA-X% were investigated using nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, wide angle X-ray diffraction, and thermogravimetric analysis. In general, the crystallinity, melting point, and thermal degradation temperature of PEBA-X% decreased as the incorporation of N-methyl functionalized groups increased, owing to the disruption caused to the structural regularity of the copolymer. However, in N-acetyl functionalized analogues, the crystallinity first dropped and then increased because of a new γ form arrangement that developed in the microstructure. After the cross-linking reaction of the N-methyl-substituted derivative, which has electron-donating characteristics, with poly(4,4′-methylenebis(phenyl isocyanate), the decomposition temperature of the resulting polymer significantly increased, whereas no such improvements could be observed in the case of the electro-withdrawing N-acetyl-substituted derivative, because of the incompleteness of its cross-linking reaction.

scholarly journals Diethylstilbestrol Modifies the Structure of Model Membranes and Is Localized Close to the First Carbons of the Fatty Acyl Chains

Biomolecules ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 220
Author(s):  
Alessio Ausili ◽  
Inés Rodríguez-González ◽  
Alejandro Torrecillas ◽  
José A. Teruel ◽  
Juan C. Gómez-Fernández
Keyword(s):  
Membrane Surface ◽  
Water Layer ◽  
Fatty Acyl ◽  
31P Nmr Spectroscopy ◽  
Relaxation Rates ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Acyl Chains ◽  
Dynamics Simulations

The synthetic estrogen diethylstilbestrol (DES) is used to treat metastatic carcinomas and prostate cancer. We studied its interaction with membranes and its localization to understand its mechanism of action and side-effects. We used differential scanning calorimetry (DSC) showing that DES fluidized the membrane and has poor solubility in DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) in the fluid state. Using small-angle X-ray diffraction (SAXD), it was observed that DES increased the thickness of the water layer between phospholipid membranes, indicating effects on the membrane surface. DSC, X-ray diffraction, and 31P-NMR spectroscopy were used to study the effect of DES on the Lα-to-HII phase transition, and it was observed that negative curvature of the membrane is promoted by DES, and this effect may be significant to understand its action on membrane enzymes. Using the 1H-NOESY-NMR-MAS technique, cross-relaxation rates for different protons of DES with POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) protons were calculated, suggesting that the most likely location of DES in the membrane is with the main axis parallel to the surface and close to the first carbons of the fatty acyl chains of POPC. Molecular dynamics simulations were in close agreements with the experimental results regarding the location of DES in phospholipids bilayers.

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