The role of calorimetry in the structural study of mesophases and their glass states

Casado, F. Javier; Riesco, M. Ramos; Yélamos, M. I. Redondo; Arenas, A. Sánchez; Cheda, J. A. R.

doi:10.1007/s10973-011-1938-2

Cited by 27 publications

(16 citation statements)

References 40 publications

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“…− and a C22 alkyl chain is needed for the case of bistriflimide ((CF 3 SO 2 ) 2 N − ) anion [29]. A similar behavior is observed in metal alkanoates: when the anion bearing the alkyl chain is paired with larger cations (e.g., from Li + to Cs + ) a longer alkyl chain is needed in order to observe the formation of ILC phases [30][31][32].…”

Section: Introductionmentioning

confidence: 77%

Comparison of the Ionic Liquid Crystal Phase of [C12C1im][BF4] and [C12C1im]Cl by Atomistic MD Simulations

Saielli

2020

Crystals

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We present fully atomistic molecular dynamics (MD) simulations at 450 K of two ionic liquid crystals in the smectic phase: 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C12C1im][BF4]) and 1-dodecyl-3-methylimidazolium chloride ([C12C1im]Cl). The two systems experimentally exhibit different ranges of thermal stability of the ionic smectic phase: The chloride salt has a more stable LC phase, between 270.3 K and 377.6 K, with a range of SmA of more than 107 K. In contrast, the tetrafluoroborate salt has a smectic phase between 299.6 K and 311.6 K, with a range of mesophase of just 12 K. The MD simulations show that the chloride system is stable in the smectic phase for the 5 ns of simulation, while the tetrafluoroborate salt melts into an isotropic ionic liquid, in qualitative agreement with the experiments. Comparison of the electrostatic and van der Waals energetic contributions enables one to rationalize the observed behavior as being due to the large size of the [BF4] anion: a larger size of the anion means a lower charge density, and therefore a weaker electrostatic interaction in the ionic layer.

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Section: Introductionmentioning

confidence: 77%

Comparison of the Ionic Liquid Crystal Phase of [C12C1im][BF4] and [C12C1im]Cl by Atomistic MD Simulations

Saielli

2020

Crystals

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“…The orientation of the catenae is alternate, as explained in the introduction (see Figures 1 and 2c), with a lamellar structure, as polymorph A, and growing also in the plane of the all-trans carboxylates. In this case, the angle between the alkyl chains is negligible, and the planes formed by the trans C atoms of the two chains show a herringbone arrangement (internal orientational order), 57 with an angle of about 45°, unlike the other two polymorphs, where those planes are almost parallel (<5°).…”

Section: Resultsmentioning

confidence: 90%

New Advances in the One-Dimensional Coordination Polymer Copper(II) Alkanoates Series: Monotropic Polymorphism and Mesomorphism

Riesco¹,

Martínez

Cheda³

et al. 2015

Crystal Growth & Design

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The polymorphism in the copper(II) alkanoates, recently discovered for one member, has been thoroughly studied for the whole series, from 3 to 16 C atoms. Three polymorphic phases have been found, all of them sharing the same molecular unit, the paddle-wheel, which grows forming a 1D coordination polymer or catena. The three polymorphs are defined by a different packing of these catenae and a specific arrangement of the alkyl chains. Ten new crystal structures of those compounds have been solved by high resolution powder diffraction and presented in this paper. The polymorphism in this series has been found to be monotropic and is responsible for the complex thermal behavior observed. The most characteristic feature, the endothermic−exothermic effect, has been explained for the first time in these compounds by a combination of data from differential scanning calorimetry (in normal and modulated modes), powder X-ray diffraction and Fourier transform infrared spectroscopy. These techniques, together with small-angle X-ray scattering and optical microscopy, were used to analyze the hexagonal columnar discotic liquid crystal phase of copper(II) alkanoates. Thus, new information has been found in the packing and stacking of the discs formed by the paddle-wheel units, also maintained in the mesophase.

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“…As a general consideration, it must be pointed out that for the thallium(I) salts all the solid phases previous to liquid crystal phase formation are really condis phases that are conformational‐disordered phases, which means that all of the chains are already melted with many ‘gauche’ defects. In fact, this type of solid mesophase is characterized by orientational order and the presence of conformational disorders in the alkyl chains, separating the polar heads (ions, metals and organic cations) in the ionic layers, which allows ‘plastic’ deformations in this layered solid phase .…”

Section: Resultsmentioning

confidence: 99%

“…The results are given in Table . A full characterization of the mesomorphic states (liquid crystal, plastic crystal, condis phase and rotator phase) of these organic salts is discussed elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…Organic salts have been widely studied for their properties, because of their characteristic amphiphilic structure: hydrophilic–hydrophobic. In particular, metal alkanoates (or metal soaps) are well‐known organic salts which are also very interesting in themselves, because they may present polymorphism and/or polymesomorphism, depending on the type of disorder of the different parts . The processes involved from the totally ordered crystal phase at low temperature to the isotropic liquid phase constitute the ‘stepwise melting mechanism’.…”

Section: Introductionmentioning

confidence: 99%

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Effect of mesogenic organic salts on vulcanization and physical properties of rubber compounds

et al. 2013

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The role of calorimetry in the structural study of mesophases and their glass states

Cited by 27 publications

References 40 publications

Comparison of the Ionic Liquid Crystal Phase of [C12C1im][BF4] and [C12C1im]Cl by Atomistic MD Simulations

Comparison of the Ionic Liquid Crystal Phase of [C12C1im][BF4] and [C12C1im]Cl by Atomistic MD Simulations

New Advances in the One-Dimensional Coordination Polymer Copper(II) Alkanoates Series: Monotropic Polymorphism and Mesomorphism

Effect of mesogenic organic salts on vulcanization and physical properties of rubber compounds

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