Thermal behaviour and electro-optical properties of a series of liquid crystals based on palladium complexes with mixed ligands

Cı̂rcu, Viorel; Mocanu, Ana S.; Roşu, Constantin; Mănăilă-Maximean, Doina; Dumitraşcu, Florea

doi:10.1007/s10973-011-1609-3

Cited by 18 publications

(6 citation statements)

References 31 publications

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“…The thermally stimulated depolarization currents method [ 33 , 34 ] and DSC are applicable for an experimental determination of the activation energy, while the DSC method has been employed in our study. Concerning the results of DSC measurements, the activation energy E A and the pre-exponential A could be determined using the Kissinger method [ 35 ].…”

Section: Methodsmentioning

confidence: 99%

“…According to resultant change of heat amount, temperature-and time-dependent crosslink density ratio of the released heat amount Hrelease to the maximum heat amount Hmax in a fully cro linked state, using Equation (4) (see Figure 2b). Figure 2c shows the reaction rate in pendency on the crosslinking degree to estimate the unknown parameter in the react model f(α): The thermally stimulated depolarization currents method [33,34] and DSC are applicable for an experimental determination of the activation energy, while the DSC method has been employed in our study. Concerning the results of DSC measurements, the activation energy E A and the pre-exponential A could be determined using the Kissinger method [35].…”

Section: Differential Scanning Calorimetrymentioning

confidence: 99%

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Characterization of Cure Behavior in Epoxy Using Molecular Dynamics Simulation Compared with Dielectric Analysis and DSC

2021

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The curing behavior of a thermosetting material that influences the properties of the material is a key issue for predicting the changes in material properties during processing. An empirical equation can describe the reaction kinetics of the curing behavior of an investigated material, which is usually estimated using experimental methods. In this study, the curing process of an epoxy resin, the polymer matrix in an epoxy molding compound, is computed concerning thermal influence using molecular dynamics. Furthermore, the accelerated reaction kinetics, which are influenced by an increased reaction cutoff distance, are investigated. As a result, the simulated crosslink density with various cutoff distances increases to plateau at a crosslink density of approx. 90% for the investigated temperatures during curing time. The reaction kinetics are derived according to the numerical results and compared with the results using experimental methods (dielectric analysis and differential scanning calorimetry), whereby the comparison shows a good agreement between experiment and simulation.

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Section: Methodsmentioning

confidence: 99%

Section: Differential Scanning Calorimetrymentioning

confidence: 99%

Characterization of Cure Behavior in Epoxy Using Molecular Dynamics Simulation Compared with Dielectric Analysis and DSC

2021

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“…Schiff bases are involved in many appealing applications in diverse fields including catalysis [14], medicine [15], corrosion chemistry [16] and photochromism [17]. They have been extensively studied for their interesting liquid crystalline properties [18][19][20][21][22][23][24] as they provide rigid core structure and enhance mesophase formation by preserving a linear geometry, higher stability and polarity of imine linkage [25].…”

Section: Introductionmentioning

confidence: 99%

Mesomorphic Behaviour and DFT Insight of Arylidene Schiff Base Liquid Crystals and Their Pyridine Impact Investigation

et al. 2021

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A new series of Schiff base liquid crystal have been prepared and studied. Schiff bases of p-alkyl aniline derivatives and 4-phenyl pyridine-4′-carbaldehyde were prepared. The terminal alkyl groups substituting aniline are of varied chain length, namely C8, C12 and C14. The structures of the compounds were elucidated by 1H NMR and 13C NMR. The mesomorphic thermal and optical characteristics of the samples were determined via differential thermal analysis (DSC) and polarization optical microscopy (POM). All compounds exhibit enantiotropic dimorphic mesophase behaviour, referred to as smectic X1 (SmX1) and smectic X2 (Sm A). Experimental results obtained for the mesophases were correlated with density functional theory (DFT) theoretical calculations. The results of the new series are further compared to two series of compounds bearing pyridine (two ring Schiff bases) and biphenyl, respectively, in their mesogens. The series of compounds of one pyridine ring are generally not mesomorphic. The results indicate that the alkyl chain length has a strong impact on the mesomorphic characteristics and thermal stabilities of the different mesophases. As a trend, the temperature ranges of both of smectic mesophases of all compounds are higher in new compounds bearing the 4-phenyl pyridine moiety. In addition, the total mesophase range is generally higher in the new compounds when compared to their biphenyl analogues. Finally, theoretical DFT calculations were performed to illustrate the experimental finding of the mesomorphic behaviour in terms of the molecular geometry and aromaticity, π–π stacking and LOL-π.

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“…Despite having a stepped core structure, it also maintains molecular linearity, resulting in greater thermal stability and enabling the formation of phase ( Ahmed et al, 2020b ; Hagar et al, 2020 ). Recently, many mesomorphic Schiff base/ester systems of low molecular mass have been designed and examined ( Jakeman and Raynes, 1972 ; Cîrcu et al, 2011 ; Al-Mutabagani et al, 2021a ; Altowyan et al, 2021 ; Al-Mutabagani et al, 2021b ; Gomha et al, 2021b ; El-Atawy et al, 2021 ). The connection of -COO– and –CH = N– linking groups and terminal long flexible chain provides flexibility to the molecule, which leads to conformational changes during the phase transition.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Mesomorphic and Electrical Investigations of New Furan Liquid Crystal Derivatives

et al. 2021

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New homologues set liquid crystalline materials, based on furfural derivatives, namely, (E)-4-((furan-2-ylmethylene)amino)phenyl 4-alkoxybenzoate (Fn), were synthesized and investigated for their mesomorphic and optical characteristics. The prepared homologues series constitutes three derivatives that bear different terminal flexible alkyl chain lengths that vary between 6 and 12 carbons and attached to the phenyl ring linked to the ester group. A furfural moiety is introduced into the other terminal of the molecular structure. Mesomorphic characterizations of the prepared derivatives were measured using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Molecular structures were elucidated via elemental analyses, FTIR, and NMR spectroscopy. DSC and POM showed that all the synthesized furfural derivatives are purely nematogenic, exhibiting an enantiotropic nematic (N) mesophase, except for the longest chain derivative (F12) that is dimorphic possessing a monotropic smectic A phase and an enantiotropic N mesophase. Results indicated that the incorporation of the heterocyclic furfural ring into the molecular skeleton affected both the mesophase range and stability of investigated homologue. Analysis of the optical properties revealed that the shortest chain compound (F6) possesses two direct band gaps, at 2.73 and 3.64 eV, in addition to higher absorption than the higher homologues, F10 and F12. On the other hand, all the synthesized homologues (Fn) showed Ohmic behaviors, with electric resistances in the GΩ range. The values of the electrical resistances are 103.71, 12.91, and 196.85 GΩ at 0.05 V for F6, F10, and F12, respectively.

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Thermal behaviour and electro-optical properties of a series of liquid crystals based on palladium complexes with mixed ligands

Cited by 18 publications

References 31 publications

Characterization of Cure Behavior in Epoxy Using Molecular Dynamics Simulation Compared with Dielectric Analysis and DSC

Characterization of Cure Behavior in Epoxy Using Molecular Dynamics Simulation Compared with Dielectric Analysis and DSC

Mesomorphic Behaviour and DFT Insight of Arylidene Schiff Base Liquid Crystals and Their Pyridine Impact Investigation

Synthesis and Mesomorphic and Electrical Investigations of New Furan Liquid Crystal Derivatives

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