Advances of isotropic to smectic phase transitions

Mukherjee, Prabir K.

doi:10.1016/j.molliq.2021.117227

Cited by 6 publications

(8 citation statements)

References 171 publications

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“…Moreover, the values of d of the SC-LCE 2 sample within the smectic A phase are similar to those obtained in similar LCE systems showing an SmA phase and containing high concentrations of M11, as a comonomer [18]. The transition from the SmA phase to the isotropic liquid, which is not usual in LCEs but is widely investigated in low-molecular weight liquid crystals [75,76], is not abrupt; instead, a smooth decrease in the diffraction signal's intensity is observed which is associated with its gradual broadening due to the continuous decrease in the correlation length of the positional order of the molecules in the isotropic liquid. As shown from the 2 H NMR results, the SmA-Iso phase transition in liquid crystalline elastomers is of a weak first order, as observed in other similar systems [10][11][12][13][14].…”

Section: Mesophase and Structural Properties Of The New Sc Lcessupporting

confidence: 80%

“…not usual in LCEs but is widely investigated in low-molecular weight liquid crystals [75,76], is not abrupt; instead, a smooth decrease in the diffraction signal's intensity is observed which is associated with its gradual broadening due to the continuous decrease in the correlation length of the positional order of the molecules in the isotropic liquid. As shown from the 2 H NMR results, the SmA-Iso phase transition in liquid crystalline elastomers is of a weak first order, as observed in other similar systems [10][11][12][13][14].…”

Section: Mesophase and Structural Properties Of The New Sc Lcesmentioning

confidence: 98%

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New Liquid Crystalline Elastomeric Films Containing a Smectic Crosslinker: Chemical and Physical Properties

et al. 2023

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Side-chain liquid crystal elastomers (SC-LCEs) have been designed by using a new smectic crosslinker. Two types of monodomain films were prepared based on polysiloxane chains, with a different relative concentration of both crosslinker and mesogenic comonomers. The mesomorphic behavior of the two SC-LCE systems was investigated by differential scanning calorimetry and polarized optical microscopy showing a different mesomorphic behavior: in one case, we obtained a nematic SC-LCE film, in the other case, a Smectic A SC-LCE film. In both systems, the mesophases were stable in a wide temperature range. Moreover, the SC-LCE films possess a relatively high orientation at room temperature. The physical-chemical properties, such as the local orientational ordering, structural organization, and dynamics of SC-LCEs’ constituents were studied by means of static and dynamic 2H NMR experiments, small-angle X-ray, and wide-angle X-ray diffractions. The relevant physical properties, such as the thermo-elastic and thermo-mechanic behaviors, are reported and discussed in view of the practical applications.

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Section: Mesophase and Structural Properties Of The New Sc Lcessupporting

confidence: 80%

Section: Mesophase and Structural Properties Of The New Sc Lcesmentioning

confidence: 98%

New Liquid Crystalline Elastomeric Films Containing a Smectic Crosslinker: Chemical and Physical Properties

et al. 2023

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“…At the same time, their centers of mass are arranged randomly; thus, only the orientational order is maintained. In the Sm phase, the molecules located within layers are arranged in planeshence, besides the orientational order, there is also a positional order. − Moreover, it should be emphasized that there are two main types of LCs: thermotropic and lyotropic liquid crystals (TLCs and LLCs), where LC phases can be induced by changing the temperature (heating or cooling) or dissolving mesogens in a suitable solvent, respectively . Therefore, it is possible to obtain various states of molecular order.…”

Section: Introductionmentioning

confidence: 99%

The Influence of PVP Polymer Topology on the Liquid Crystalline Order of Itraconazole in Binary Systems

Orszulak,

Lamrani,

Bernat

et al. 2024

Mol. Pharmaceutics

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This study presents a novel approach by utilizing poly-(vinylpyrrolidone)s (PVPs) with various topologies as potential matrices for the liquid crystalline (LC) active pharmaceutical ingredient itraconazole (ITZ). We examined amorphous solid dispersions (ASDs) composed of ITZ and (i) self-synthesized linear PVP, (ii) self-synthesized star-shaped PVP, and (iii) commercial linear PVP K30. Differential scanning calorimetry, X-ray diffraction, and broad-band dielectric spectroscopy were employed to get a comprehensive insight into the thermal and structural properties, as well as global and local molecular dynamics of ITZ−PVP systems. The primary objective was to assess the influence of PVPs' topology and the composition of ASD on the LC ordering, changes in the temperature of transitions between mesophases, the rate of their restoration, and finally the solubility of ITZ in the prepared ASDs. Our research clearly showed that regardless of the PVP type, both LC transitions, from smectic (Sm) to nematic (N) and from N to isotropic (I) phases, are effectively suppressed. Moreover, a significant difference in the miscibility of different PVPs with the investigated API was found. This phenomenon also affected the solubility of API, which was the greatest, up to 100 μg/mL in the case of starPVP 85:15 w/w mixture in comparison to neat crystalline API (5 μg/mL). Obtained data emphasize the crucial role of the polymer's topology in designing new pharmaceutical formulations.

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“…• What are the shortest path directions connecting minima? Previous works have excellently characterized these mesophases and phase transitions, including phase diagrams, orientation distribution function profiles, bifurcation analysis, and the use of imaging techniques, calorimetry characterization, and dynamic simulations, accentuating the thermodynamic I-SmA phase transition perspective (Palffy-Muhoray, 1999;Dogic and Fraden, 2001;Mukherjee et al, 2001;Larin, 2004;Urban et al, 2005;Biscari et al, 2007;Das and Mukherjee, 2009;Chahine et al, 2010;Nandi et al, 2012;Izzo and De Oliveira, 2019;Gudimalla et al, 2021;Khan and Mukherjee, 2021;Mukherjee, 2021). Given that the first four key issues are essentially anchored in the spatial features of the energy landscape, we develop, implement, and validate a novel geometric methodology.…”

Section: Introductionmentioning

confidence: 99%

Geometric modeling of phase ordering for the isotropic–smectic A phase transition

Zamora Cisneros,

Wang,

Dorval Courchesne

et al. 2024

Front. Soft Matter

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BackgroundLiquid crystal (LC) mesophases have an orientational and positional order that can be found in both synthetic and biological materials. These orders are maintained until some parameter, mainly the temperature or concentration, is changed, inducing a phase transition. Among these transitions, a special sequence of mesophases has been observed, in which priority is given to the direct smectic liquid crystal transition. The description of these transitions is carried out using the Landau–de Gennes (LdG) model, which correlates the free energy of the system with the orientational and positional order.MethodologyThis work explored the direct isotropic-to-smectic A transition studying the free energy landscape constructed with the LdG model and its relation to three curve families: (I) level-set curves, steepest descent, and critical points; (II) lines of curvature (LOC) and geodesics, which are directly connected to the principal curvatures; and (III) the Casorati curvature and shape coefficient that describe the local surface geometries resemblance (sphere, cylinder, and saddle).ResultsThe experimental data on 12-cyanobiphenyl were used to study the three curve families. The presence of unstable nematic and metastable plastic crystal information was found to add information to the already developed smectic A phase diagram. The lines of curvature and geodesics were calculated and laid out on the energy landscape, which highlighted the energetic pathways connecting critical points. The Casorati curvature and shape coefficient were computed, and in addition to the previous family, they framed a geometric region that describes the phase transition zone.Conclusion and significanceA direct link between the energy landscape’s topological geometry, phase transitions, and relevant critical points was established. The shape coefficient delineates a stability zone in which the phase transition develops. The methodology significantly reduces the impact of unknown parametric data. Symmetry breaking with two order parameters (OPs) may lead to novel phase transformation kinetics and droplets with partially ordered surface structures.

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Advances of isotropic to smectic phase transitions

Cited by 6 publications

References 171 publications

New Liquid Crystalline Elastomeric Films Containing a Smectic Crosslinker: Chemical and Physical Properties

New Liquid Crystalline Elastomeric Films Containing a Smectic Crosslinker: Chemical and Physical Properties

The Influence of PVP Polymer Topology on the Liquid Crystalline Order of Itraconazole in Binary Systems

Geometric modeling of phase ordering for the isotropic–smectic A phase transition

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