Reply to the ‘Comment on “Polymorphism of levofloxacin: structure, properties and phase transformation”’ by Tejender S. Thakur, CrystEngComm, 2020, 22, DOI: 10.1039/C9CE01400D

CrystEngComm ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1889-1891
Author(s):  
Ning Wei ◽  
Mingtao Zhang ◽  
Jingtao Chen ◽  
Junbo Gong ◽  
Songgu Wu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Molecular Conformation ◽  
Stable Conformer ◽  
Structural Differences ◽  
Structure Properties

Minor structural differences in molecular conformation were found where the levofloxacin molecule takes a less stable conformer in energy rather than the stable conformer as previously expected.

Thermal, spectroscopic and structural analysis of a thermosalient phase transformation in tapentadol hydrochloride

2019 ◽  
Vol 75 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Pablo Gaztañaga ◽  
Ricardo Baggio ◽  
Emilia Halac ◽  
Daniel R. Vega
Keyword(s):  
Phase Transformation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Covalent Interaction ◽  
Cell Parameters ◽  
Reversible Phase Transition ◽  
Abrupt Changes ◽  
Structural Differences ◽  
Interaction Scheme ◽  
Reversible Phase

Presented herein are detailed optical, thermal, spectroscopic and structural analyses of the phase transformation occurring in tapentadol hydrochloride (C14H24NO+·Cl−), a phenomenon already reported [Fischer et al. (2006); Patent: WO 2006000441 A2]. The thermal behaviour of the compound was studied using single-crystal X-ray diffraction, differential scanning calorimetry and Raman scattering measurements. The compound undergoes a first-order reversible phase transition at T heat = 318.0 (1) K, T cool = 300.0 (1) K, as assessed by the coexistence of both phases in the vicinity of the transition and the abrupt changes observed in the unit-cell parameters with temperature. The process is accompanied by clear thermosalient behaviour, with a conspicuous movement of the samples. On cooling, the transformation leads from a P212121 symmetry (Z′ = 1) to P21, with an abrupt change in β [90 ↔ 94.78 (1)°] and duplication of the asymmetric unit contents (Z′ = 2). The main structural differences observed across the transition are extremely small, with almost no changes in the stronger, non-covalent interaction scheme involving the `conventional' (N—H...Cl, O—H...Cl) hydrogen bonds.

scholarly journals Structure–Properties Relationship in Waterborne Poly(Urethane-Urea)s Synthesized with Dimethylolpropionic Acid (DMPA) Internal Emulsifier Added before, during and after Prepolymer Formation

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2478
Author(s):  
Mónica Fuensanta ◽  
Abbas Khoshnood ◽  
José Miguel Martín-Martínez
Keyword(s):  
Particle Size ◽  
Phase Separation ◽  
Ph Value ◽  
Peel Test ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Adhesion Properties ◽  
Structural Differences ◽  
Higher Temperature ◽  
Structure Properties

Dimethylolpropionic acid (DMPA) internal emulsifier has been added before, during and after prepolymer formation in the synthesis of waterborne poly(urethane-urea)s (PUDs) and their structure–properties relationships have been assessed. PUDs were characterized by pH, viscosity and particle size measurements, and the structure of the poly(urethane-urea) (PU) films was assessed by infra-red spectroscopy, differential scanning calorimetry, X-ray diffraction, thermal gravimetric analysis, plate–plate rheology and dynamic mechanical thermal analysis. The adhesion properties of the PUDs were measured by cross-hatch adhesion and T-peel test. The lowest pH value and the highest mean particle size were found in the PUD made by adding DMPA after prepolymer formation, all PUDs showed relatively ample mono-modal particle size distributions. The highest viscosity and noticeable shear thinning were obtained in the PUD made by adding DMPA during prepolymer formation. Depending on the stage of addition of DMPA, the length of the prepolymer varied and the PU films showed different degree of micro-phase separation. Because the shortest prepolymer was formed in the PU made with DMPA added before prepolymer, this PU film showed the lowest storage moduli and early melting indicating higher degree of micro-phase separation. The highest storage modulus, later melting, higher temperature and lower modulus at the cross between the storage and loss moduli corresponded to the PU made by adding DMPA after prepolymer formation, because the longer prepolymer produced during synthesis. The lowest thermal stability corresponded to the PU made by adding DMPA during prepolymer formation and the structures of all PU films were dominated by the soft domains, the main structural differences derived from the hard domains. Whereas DMPA-isophorone diisocyanate (IPDI) urethane and urea hard domains were created in the PU film made by adding DMPA during prepolymer formation, the other PU films showed DMPA-IPDI, polyester-IPDI and two different DMPA-IPDI-polyester hard domains. Finally, the adhesion properties of the PUDs and PU coatings were excellent and they were not influenced by the structural differences caused by adding DMPA in different stages of the synthesis.

Comment on “Polymorphism of levofloxacin: structure, properties and phase transformation” by N. Wei, L. Jia, Z. Shang, J. Gong, S. Wu, J. Wang and W. Tang, CrystEngComm, 2019, 21, 6196–6207

CrystEngComm ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1885-1888 ◽  
Author(s):  
Tejender S. Thakur
Keyword(s):  
Phase Transformation ◽  
Structure Properties

A comment on a statement made by W. Tang et al. on the levofloxacin polymorphs predicted through CSP studies.

Understanding metastable phase transformation during crystallization of RDX, HMX and CL-20: experimental and DFT studies

2016 ◽  
Vol 18 (34) ◽  
pp. 23554-23571 ◽  
Author(s):  
Mrinal Ghosh ◽  
Shaibal Banerjee ◽  
Md Abdul Shafeeuulla Khan ◽  
Nirmala Sikder ◽  
Arun Kanti Sikder
Keyword(s):  
Phase Transformation ◽  
Relative Stability ◽  
Molecular Conformation ◽  
Metastable Phase ◽  
Metastable Phases ◽  
Dft Studies ◽  
The Stability

The relative stability of metastable phases of RDX, HMX and CL-20 in solution has been revealed by experimental and DFT studies. Molecular conformation during prenucleation clustering and lattice barrier essentially determines the stability of metastable phases during crystallization.

Polymorphism of levofloxacin: structure, properties and phase transformation

CrystEngComm ◽  
2019 ◽  
Vol 21 (41) ◽  
pp. 6196-6207 ◽  
Author(s):  
Ning Wei ◽  
Lina Jia ◽  
Zeren Shang ◽  
Junbo Gong ◽  
Songgu Wu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Acetic Acid ◽  
Solid State ◽  
Ethylene Glycol ◽  
Crystal Forms ◽  
Structure Properties

The landscape of solid-state crystal forms of levofloxacin is further expanded with one solved anhydrous α form and three newly discovered solvates including n-propanol solvate, ethylene glycol solvate and acetic acid solvate.

Phase Transformation In Ti-6al-4v Alloys

1972 ◽  
Vol 30 ◽  
pp. 584-585
Author(s):  
Shiro Fujishiro
Keyword(s):  
Phase Transformation ◽  
Grain Boundary ◽  
Cryogenic Temperature ◽  
Β Phase ◽  
Heat Treated ◽  
Mixed Microstructure ◽  
Ductile Behavior

The Ti-6 wt.% Al-4 wt.% V commercial alloys have exhibited an improved formability at cryogenic temperature when the alloys were heat-treated prior to the tests. The author was interested in further investigating this unusual ductile behavior which may be associated with the strain-induced transformation or twinning of the a phase, enhanced at lower temperatures. The starting materials, supplied by RMI Co., Niles, Ohio were rolled mill products in the form of 40 mil sheets. The microstructure of the as-received materials contained mainly ellipsoidal α grains measuring between 1 and 5μ. The β phase formed an undefined grain boundary around the a grains. The specimens were homogenized at 1050°C for one hour, followed by aging at 500°C for two hours, and then quenched in water to produce the α/β mixed microstructure.

High Resolution Observations of Ion-Milling Induced Transformation in Synthetic Hollandses

1981 ◽  
Vol 39 ◽  
pp. 114-115 ◽  
Author(s):  
T. J. Headley
Keyword(s):  
High Resolution ◽  
Radioactive Waste Disposal ◽  
Ion Milling ◽  
Minor Elements ◽  
Waste Forms ◽  
Carbon Substrates ◽  
Structural Differences ◽  
Oxide Phases ◽  
Argon Ions ◽  
High Resolution Microscopy

Oxide phases having the hollandite structure have been identified in multiphase ceramic waste forms being developed for radioactive waste disposal. High resolution studies of phases in the waste forms described in Ref. [2] were initiated to examine them for fine scale structural differences compared to natural mineral analogs. Two hollandites were studied: a (Ba,Cs,K)-titan-ate with minor elements in solution that is produced in the waste forms, and a synthesized BaAl2Ti6O16 phase containing ∼ 4.7 wt% Cs2O. Both materials were consolidated by hot pressing at temperatures above 1100°C. Samples for high resolution microscopy were prepared both by ion-milling (7kV argon ions) and by crushing and dispersing the fragments on holey carbon substrates. The high resolution studies were performed in a JEM 200CX/SEG operating at 200kV.

Microstructural and Microchemical Characterization of Nickel Sulfide Inclusions in Plate Glass

1991 ◽  
Vol 49 ◽  
pp. 962-963
Author(s):  
J. Cooper ◽  
O. Popoola ◽  
W. M. Kriven
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
Glass Matrix ◽  
Nickel Sulfide ◽  
Plate Glass ◽  
Thermal Expansion Mismatch ◽  
Volume Increase ◽  
Β Phase ◽  
Microchemical Characterization

Nickel sulfide inclusions have been implicated in the spontaneous fracture of large windows of tempered plate glass. Two alternative explanations for the fracture-initiating behaviour of these inclusions have been proposed: (1) the volume increase which accompanies the α to β phase transformation in stoichiometric NiS, and (2) the thermal expansion mismatch between the nickel sulfide phases and the glass matrix. The microstructure and microchemistry of the small inclusions (80 to 250 μm spheres), needed to determine the cause of fracture, have not been well characterized hitherto. The aim of this communication is to report a detailed TEM and EDS study of the inclusions.

AEM of reaction-bonded SiC

1992 ◽  
Vol 50 (1) ◽  
pp. 344-345
Author(s):  
K Das Chowdhury ◽  
R. W. Carpenter ◽  
W. Braue
Keyword(s):  
Mechanical Properties ◽  
Phase Transformation ◽  
High Temperature ◽  
Epitaxial Growth ◽  
Liquid Silicon ◽  
Structural Ceramic ◽  
Few Data

Research on reaction-bonded SiC (RBSiC) is aimed at developing a reliable structural ceramic with improved mechanical properties. The starting materials for RBSiC were Si,C and α-SiC powder. The formation of the complex microstructure of RBSiC involves (i) solution of carbon in liquid silicon, (ii) nucleation and epitaxial growth of secondary β-SiC on the original α-SiC grains followed by (iii) β>α-SiC phase transformation of newly formed SiC. Due to their coherent nature, epitaxial SiC/SiC interfaces are considered to be segregation-free and “strong” with respect to their effect on the mechanical properties of RBSiC. But the “weak” Si/SiC interface limits its use in high temperature situations. However, few data exist on the structure and chemistry of these interfaces. Microanalytical results obtained by parallel EELS and HREM imaging are reported here.

Trace nanoanalysis

1994 ◽  
Vol 52 ◽  
pp. 940-941
Author(s):  
D. E. Newbury ◽  
R. D. Leapman
Keyword(s):  
High Performance ◽  
Secondary Ion Mass Spectrometry ◽  
Detection Efficiency ◽  
Volume Element ◽  
And Performance ◽  
Trace Constituents ◽  
Secondary Ion ◽  
Concentration Levels ◽  
Structure Properties

Trace constituents, which can be very loosely defined as those present at concentration levels below 1 percent, often exert influence on structure, properties, and performance far greater than what might be estimated from their proportion alone. Defining the role of trace constituents in the microstructure, or indeed even determining their location, makes great demands on the available array of microanalytical tools. These demands become increasingly more challenging as the dimensions of the volume element to be probed become smaller. For example, a cubic volume element of silicon with an edge dimension of 1 micrometer contains approximately 5×1010 atoms. High performance secondary ion mass spectrometry (SIMS) can be used to measure trace constituents to levels of hundreds of parts per billion from such a volume element (e. g., detection of at least 100 atoms to give 10% reproducibility with an overall detection efficiency of 1%, considering ionization, transmission, and counting).

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