Manoj K. Saini

Yanshan University

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Li‐Min Wang

Tianjin University of Commerce

Tao Wu

Huzhou University

K. L. Ngai

Institute for Chemical and Physical Processes

Ying Dan Liu

Yanshan University

Xiao Jin

Yanshan University

S. Srinivasa Murthy

Indian Institute of Science Bangalore

Yuxing Guo

Yanshan University

Dechao Zhang

China Mobile (China)

Long Zhang

Chongqing University of Science and Technology

Di Xu

Wuhan University

Cooperative Institutions

Yanshan University

State Key Laboratory of Metastable Materials Science and Technology

Harbin Institute of Technology

Institute for Chemical and Physical Processes

Materials Science & Engineering

Southwest Jiaotong University

Indian Institute of Science Bangalore

Bangalore University

Lawrence Berkeley National Laboratory

Indian Institute of Technology Delhi

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Dielectric spectroscopy in crystalline methocarbamol

AIP conference proceedings (2014)

Manoj K. Saini

We have used dielectric spectroscopy (20 Hz – 1 MHz) above liquid nitrogen temperature to study the room temperature crystalline phase of the methocarbamol (ML). The as received crystalline sample of ML shows a process (designated as β1) which is Arrhenius in nature in the dielectric measurements. It is also found to be non-Debye in nature. Annealing above 373 K for an hour the magnitude of this process came down by a factor of four indicating this to be due to water. Also found in crystalline phase another sub-Tg process (designated as β2) in temperature range 140K–170 K.

Atmospheric temperature range

Liquid nitrogen

10.1063/1.4872728

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Citations (0)

Equivalence of enthalpic nature of the glasses produced by crystal-damage and melt-quenching

Journal of Alloys and Compounds (2018)

Di Xu Manoj K. Saini Dechao Zhang Long Zhang Ying Dan Liu

Supercooling

Crystal (programming language)

Glass melting

10.1016/j.jallcom.2018.11.365

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Citations (3)

DSC method: Determination of amorphous fraction in solid dosage and fragility

AIP conference proceedings (2015)

Manoj K. Saini

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Manoj K. Saini; DSC method: Determination of amorphous fraction in solid dosage and fragility. AIP Conference Proceedings 24 June 2015; 1665 (1): 070022. https://doi.org/10.1063/1.4917886 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

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Fraction (chemistry)

10.1063/1.4917886

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Citations (1)

Dielectric Spectroscopy in Ibuprofen-Dioxane Mixture

Pharmaceutica Analytica Acta (2017)

Manoj K. Saini

In recent years, the dielectric study of amorphous pharmaceuticals has made a considerable effort towards correlating the molecular mobility with their physical and chemical stability.The molecular mobility of amorphous materials is affected by temperature, additives (such as water) and specific interactions (such as Hydrogen bond).Therefore, to understand the physicochemical instability of amorphous materials, nature of their molecular mobility needs to comprehend.In this order, the Dielectric and Calorimetric measurements were performed on a mixture of ibuprofen and 1,4-dioxane.The dielectric spectroscopy reveals two relaxation processes, (designated as α D , and α) in the supercooled region.The spectral shape of α D and α process can be explained satisfactorily throughout the frequency range using Havriliak-Negami (HN) shape function.The α D process is found to be Debye-like (i.e., α HN = 0 and β HN = 1) in nature and α process kinetically freezes at T g-onset (DSC) implies that α-process indeed corresponds to the glass transition event.Both processes are found to be non-Arrhenius in nature.In addition, two secondary relaxation processes (designated as β JG and β) are observed and are comparable with the literature.The activation energy of β process indicates that it"s originating from the fluctuations of the side group larger than -OH group.Also, the calculated fragility index demonstrates that ibuprofen is a fragile glass former.

Ibuprofen

10.4172/2153-2435.1000572

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Deviations of dynamic parameters characterizing enthalpic and dielectric relaxations in glass forming alkyl phosphates

The Journal of Chemical Physics (2018)

Manoj K. Saini Yuxing Guo Tao Wu K. L. Ngai Li‐Min Wang

In our recent study [T. Wu et al., J. Chem. Phys. 147, 134501 (2017)], an alkyl phosphate glass former was studied and it suggested that the enthalpy relaxation involving the motions of all parts of the molecule is global, while the dielectric relaxation detects the local rotation of the polar core. In this work, we study a series of trialkyl phosphates using calorimetric and dielectric measurements over a wide temperature range. The results indicate a departure of the dielectric fragility indexes from the enthalpic ones as the length of the branch chain increases in the trialkyl phosphates. The Kirkwood correlation factor (gk) is found to coincide at ∼0.6 at glass transition temperature (Tg) from triethyl phosphate to tributyl phosphate, indicating a similar structural alignment. The enthalpic relaxation serving as the more fundamental relaxation relevant to the structural relaxation is confirmed. Strikingly, we observed the relation of Tg to the chain length in alkyl phosphates, revealing a minimum Tg behavior, and its explanation assists in the understanding of the glass transition in relation to the structure of the glass-formers.

10.1063/1.5051570

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Citations (9)

Presence of global and local α-relaxations in an alkyl phosphate glass former

The Journal of Chemical Physics (2017)

Tao Wu Xiao Jin Manoj K. Saini Ying Dan Liu K. L. Ngai

The dynamics of a molecular glass former, tributyl phosphate (TBP), with an alkyl phosphate structure (three alkyl branches emanating from a polar core of PO4) is studied in the supercooled regime by dielectric and thermal (or enthalpic) relaxations. The dielectric fragility index md and the stretching exponent βd of the Kohlrausch-Williams-Watts correlation function are determined. Analyses of the enthalpic relaxation data by the Tool-Narayanaswamy-Moynihan-Hodge formalism yield the enthalpic fragility index mH and stretching exponent βH. The large difference between the dielectric md and the enthalpic mH, as well as between βd and βH, is a remarkable finding. The differences are interpreted by the formation of molecular self-assemblies. The interpretation is supported by the quite comparable fragility determined by viscosity and the enthalpic relaxation. The Kirkwood factor calculated at low temperatures is also consistent with the interpretation. The results suggest that the enthalpic relaxation involving the motions of all parts of TBP is global, while the dielectric relaxation detects the local rotation, which might originate from the rotation of the dipole moment of the core. The presence of two structural α-relaxations, one global and one local, with a large difference in dynamics is revealed for the first time in a molecular glass former.

Supercooling

Exponent

10.1063/1.4994868

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Citations (18)

Interplay of intermolecular interactions and flexibility to mediate glass forming ability and fragility: A study of chemical analogs

The Journal of Chemical Physics (2018)

Manoj K. Saini Xiao Jin Tao Wu Ying Dan Liu Li‐Min Wang

We have investigated the enthalpic and dielectric relaxations of four groups of quinoline analogs having similar structural properties (i.e., rigidity, stiffness, and bulkiness) but a different steric character and the nature of intermolecular interactions and flexibility. The dielectric fragility index (md) and the enthalpic one (mH), determined by the Tool-Narayanaswamy-Moynihan-Hodge formalism, are comparable. Generally, for the four sets of molecules of similar structures, both the interactions and flexibility are found to be critical in making the large span of fragility (i.e., from 59 to 131) and glass forming ability. By contrast, individual impacts of the interaction and flexibility can only explain fragility partly among each group of isomers. We found that the molecules with high fragility are of relatively low liquid density, reflecting the joint impact of the interactions and flexibility. An interesting result is observed among the isomers that the molecules which are fragile have enhanced glass forming ability. The results are unveiling the joint impacts of molecular structure (flexibility) and intermolecular interaction on the molecular dynamics.

Rigidity (electromagnetism)

Intermolecular interaction

10.1063/1.5019968

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Citations (21)

Glass Formation in Binary Solutions of Acetaminophen with Guaifenesin and Mephenesin

Journal of Solution Chemistry (2015)

Manoj K. Saini S. Srinivasa Murthy

Acetaminophen

10.1007/s10953-015-0364-7

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Citations (4)