Substrate‐Induced Crystal Plastic Phase of a Discotic Liquid Crystal

Gbabode, Gabin; Dumont, Nicolas; Quist, Florence; Schweicher, Guillaume; Moser, A.; Viville, Pascal; Lazzaroni, Roberto; Geerts, Yves

doi:10.1002/adma.201103739

Cited by 28 publications

(24 citation statements)

References 74 publications

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“…The situation might even be more complex when a wetting layer is present, i.e., a liquid‐like monolayer of molecules sandwiched between the substrate and the crystal structure, as illustrated for dihexylterthiophene 41 in Figure . Most of the time, SIPs have a kinetic origin, but in some rare cases, the substrate catalyzes the formation of a more thermodynamically stable phase . The situation is not different in bulk.…”

Section: Charge Transportmentioning

confidence: 99%

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

et al. 2020

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The field of organic electronics has been prolific in the last couple of years, leading to the design and synthesis of several molecular semiconductors presenting a mobility in excess of 10 cm2 V−1 s−1. However, it is also started to recently falter, as a result of doubtful mobility extractions and reduced industrial interest. This critical review addresses the community of chemists and materials scientists to share with it a critical analysis of the best performing molecular semiconductors and of the inherent charge transport physics that takes place in them. The goal is to inspire chemists and materials scientists and to give them hope that the field of molecular semiconductors for logic operations is not engaged into a dead end. To the contrary, it offers plenty of research opportunities in materials chemistry.

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Section: Charge Transportmentioning

confidence: 99%

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

et al. 2020

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“…The bulk thermotropic properties of 16 are well characterized, it exhibits a columnar rectangular phase (Col r ) at room temperature, transforming into a columnar hexagonal phase (Col h ) at ≈58 °C, before the onset of melting upon further heating at ≈182 °C . The study of the SIP of 16 showed that the structure is a columnar tetragonal (Col tet ) PC phase exhibiting three‐dimensional order, markedly different from the bulk LC form with a columnar rectangular (Col r ) structure . The SIP forms independent of the thickness of the films and the nature of the substrate, but it is dependent on the time for which the films are aged ( Figure ).…”

Section: Experimentally Observed Sipsmentioning

confidence: 99%

Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces

Jones

Chattopadhyay

Geerts

et al. 2016

Adv Funct Materials

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2233wileyonlinelibrary.com to that of the bulk liquid; [ 7 ] order typically exists over a few molecular layers before rapidly decaying to bulk behavior as the distance from the wall increases. [ 8 ] Similar ordering effects can also be observed in the quasiliquids which form on the surface of many solids due to surface melting (also known as premelting): [ 9,10 ] the existence of a liquid-like layer a few molecules thick on the surface of a solid below the melting point of the bulk material. [ 11 ] The structure within this layer is also found to be different to that of the bulk isotropic liquid, [ 12 ] highlighting the ordering occurring at the interface. A converse effect, surface freezing, is also observed in some liquids (primarily n -alkanes with 16 ≤ n ≤ 50), where a solid monolayer may exist at an interface up to ≈30 °C above the bulk melting point while the rest of the compound is molten. [13][14][15] Such phase behavior is strongly dependent on molecular shape and has only been observed for chain molecules, which then form layers similar to self-assembled monolayers (SAMs) at the interface with the liquid bulk. [ 16 ] Further examples of molecular ordering at interfaces can be seen in materials which display liquid crystal (LC) phases, a phase behavior also dependent on molecular shape and generally observed for molecules with a highly anisotropic shape (e.g., rod-like, disc-like or bowl-like molecules). [ 17 ] LCs have properties of both solids and liquids and display long range order which may be orientational and/or positional; various types of LC phases (mesophases) are possible and normally exist only over a certain temperature range (i.e., they are thermotropic); a further property of LCs is that they generally reach thermodynamic equilibrium in the bulk and at interfaces as a result of their short relaxation time. Nematic (N) phases of calamitic LCs (rod-like molecules with cylindrical symmetry) have no positional order but an orientational order which can be described by a unit vector, n , known as the director, which represents the preferred molecular orientation ( Figure 1 , left). A scalar order parameter can also be defi ned which is related to the average angle the long molecular axes make to the director, n .Increased order is seen in smetic phases (Sm) which have both orientational and positional order; for example in a smetic A phase (SmA) molecules form layers (positional ordering of the molecular mass centers) which are oriented normal to the plane of the layers (orientational order), while smetic C phases (SmC) form layers where molecules are oriented with the long molecular axes tilted at an angle to the molecular layer normal However, the factors that drive such a process are not clearly understood or studied in depth. In this feature article, we review the current state of understanding concerning SIPs, giving examples of systems where SIPs have been observed, discussing their origins, and which questions remain to be answered. The role of the substrate in controlling the growth a...

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“…Damit wird es möglich, dünne, orientierte Filme aus Mesogen (16) auch durch Gasphasenabscheidung auf Oberflächen aufzubringen. Geerts et al zeigten für Phthalocyanin‐Mesogene, dass sich die Struktur an Grenzflächen von der Volumenphase unterscheidet 26. Solche Kenntnisse sind bedeutend für die Anwendung der Materialien in der organischen Elektronik.…”

Section: Flüssigkristalleunclassified

The quaternary structure of tetrameric hemoglobin regulates the oxygen affinity of polymerized hemoglobin

Palmer

Sun

Harris

2009

Biotechnology Progress

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This study focuses on the effect of the initial quaternary structure of bovine hemoglobin (Hb) on the physical properties of glutaraldehyde polymerized Hb (PolyHb) solutions. Tense (T) state PolyHb was synthesized by maintaining the pO(2) of Hb before and after polymerization at 0 mm Hg. In contrast, relaxed (R) state PolyHb was generated by maintaining the pO(2) of Hb before and after polymerization to >749 mm Hg. PolyHb solutions were characterized by measuring the pO(2), methemoglobin (metHb) level, molecular weight distribution, O(2) affinity and cooperativity coefficient. The metHb level of all PolyHb solutions was low (<2%). Analysis of the molecular weight distribution of PolyHb solutions indicates that in general, the molecular weight of PolyHb solutions increased with increasing cross-link density. T-state PolyHb solutions exhibited lower O(2) affinity compared to unmodified Hb, whereas R-state PolyHb solutions exhibited higher O(2) affinity compared to unmodified Hb. In addition, the polymerization reaction resulted in a significant decrease in cooperativity that was more pronounced at higher cross-link densities. All of these results were explained in terms of the quaternary structure of Hb. Taken together, our results yield more insight into the importance Hb's quaternary structure plays in defining the physical properties of glutaraldehyde PolyHb solutions. This information will be useful in designing optimized glutaraldehyde PolyHb oxygen carriers for various applications in transfusion medicine.

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Substrate‐Induced Crystal Plastic Phase of a Discotic Liquid Crystal

Cited by 28 publications

References 74 publications

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces

The quaternary structure of tetrameric hemoglobin regulates the oxygen affinity of polymerized hemoglobin

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