Liquid crystalline properties of all symmetric p-phenylene and 2,5-thiophene pentamers

Kuiper, Stefan; Jager, Wolter F.; Dingemans, Theo J.; Picken, Stephen J.

doi:10.1080/02678290902923410

Cited by 18 publications

(16 citation statements)

References 16 publications

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“…[ 28 ] The tunability of the molecular alignment with surfaces, magnetic and electric fi elds offered by such phases can be in principle exploited to control the morphology of the semiconductor. Indeed, although in the specifi c case of T6 the crystal-LC phase transition occurs at high temperature, posing severe diffi culties to practical applications, other similar materials, such as phenyl-thienyl all-aromatic co-oligomers, [ 57 ] or other alkyl substituted aromatic compounds, [ 58,59 ] present similar phases at more manageable temperatures. Conversely, the high temperatures of T6 LC phases are not an issue in computer simulations, therefore here, as a proof of principle, we could investigate the behavior of liquid crystalline T6 on the C 60 (001) surface without encountering any technical diffi culty.…”

Section: High Temperature Annealing Of the T6/c 60 (001) Interfacementioning

confidence: 99%

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

D’Avino

Muccioli

Zannoni

2014

Adv Funct Materials

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1wileyonlinelibrary.com in favorable cases by atomistic molecular dynamics (MD) simulations. [ 9,[13][14][15][16] Further development in improving the performance of OSC requires a deeper knowledge and ability to control the molecular organization at the interface between the materials playing the role of electron donor and acceptor. Important factors are the choice of donors and acceptors chemical nature, their morphology and the type of heterojunction, which currently consists of either a planar interface between two thin layers of donor and acceptor (bilayer cell, [ 17 ] possibly replicated) tandem cells, [ 18,19 ] or an interpenetrated bicontinuous arrangement where the D, A materials are microsegregated inside a single photoactive layer (bulk heterojunction or BHJ). [ 20,21 ] The orientation of donor and acceptor molecules at their interface and in particular the possibility of, say, "face-face" instead of "edge on" disposition of the respective aromatic moieties is of great importance for bilayer, as well as for BHJ cell performances. [ 22,23 ] As far as materials are concerned, both small molecules and polymers have and are being used. In general terms of efficiency polymer based devices, more extensively studied, have shown the best top performance, but small molecule cells are now showing similar results. [ 24,25 ] Small molecules have the advantage of being of a well-defi ned chemical composition: they can be easily purifi ed and their physical properties can be determined and controlled favoring a better reproducibility of solar cell performance with respect to the batch to batch variations often found in polymers. While chemical composition represents an essential aspect, polymorphism for crystalline materials or more generally the detailed molecular arrangement in space (e.g., the type of mesophase for liquid crystalline materials) [ 26 ] plays an important role. For small molecule materials these aspects can be thermodynamically controlled and well defi ned reaching equilibrium conditions at a certain temperature T , pressure P , and composition. However molecular organizations can very signifi cantly change in thin nanometric fi lms and, moreover, the fi lm preparation process can be a nonequilibrium one making the fi nal result even more diffi cult to predict.Here we wish to investigate the possibility of controlling morphology at a donor-acceptor interface prepared with a physical vapor deposition process, applying a methodology we have recently developed and applied to the deposition of pentacene From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C 60Gabriele D'Avino , Luca Muccioli , and Claudio Zannoni* A theoretical investigation of the molecular organization at a sexithiophene (T6)-C 60 fullerene planar heterojunction, based on atomistic molecular dynamics, is presented, in which the effect of two different sample preparation processes on the resulting interface morphology is explored. First, the landing of T6 on C 60 (001) substrate is consid...

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Section: High Temperature Annealing Of the T6/c 60 (001) Interfacementioning

confidence: 99%

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

D’Avino

Muccioli

Zannoni

2014

Adv Funct Materials

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“…While there are examples of real mesogens without flexible tails, e.g. p-quenquiphenyl [13], in general the tails play a pivotal role in stabilising the mesophase relative to the crystal, and often determine the phase type (nematic or smectic). In order to capture the interplay between mesogen symmetry and phase symmetry, especially the cooperative selection of mesogen statistical shapes and spontaneous symmetry breaking, more realistic models of mesogenic architectures are essential.…”

Section: Mesogen Statistical Shapementioning

confidence: 99%

meta-Cybotaxis and nematic biaxiality

Samulski

2010

Liquid Crystals

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In 1970, two seemingly unrelated reports about nematic liquid crystals appeared in the scientific literature: at Kent State University, Adrian de Vries reported local smectic order in a nematic that he termed cybotactic, and at IBM, Marvin Freiser showed the possibility of a lower symmetry nematic that he named biaxial. These two discoveries are connected through consideration of the origins of spontaneous symmetry breaking, in particular, how broken symmetry within transient clusters permeating a nominally uniaxial nematic may lead to a biaxial nematic.

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“…[25] Interestingly, quinquephenyl and polyphenyl derivatives have long been prototype molecules for organic electronics, along with oligothiophenes. [22,31,32] In view of this multiplicity of interests, we wish to provide a simu-lation of quinquephenyl at the full atomistic level of detail, that allows us to develop a suitable FF, validate it, and calculate liquid-crystal properties as well as assess its actual rigidity. [30] Among the liquid-crystalline derivatives, several have been synthesized with a lower clearing temperature than that of P5.…”

Section: Introductionmentioning

confidence: 99%

“…[30] Among the liquid-crystalline derivatives, several have been synthesized with a lower clearing temperature than that of P5. [22,31,32] In view of this multiplicity of interests, we wish to provide a simu-lation of quinquephenyl at the full atomistic level of detail, that allows us to develop a suitable FF, validate it, and calculate liquid-crystal properties as well as assess its actual rigidity. We also discuss classical liquid-crystal theories in the light of these results.…”

Section: Introductionmentioning

confidence: 99%

Quinquephenyl: The Simplest Rigid‐Rod‐Like Nematic Liquid Crystal, or is it? An Atomistic Simulation

2014

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We have performed an atomistic molecular-dynamics study on the molecular organization and liquid-crystalline properties of quinquephenyl (P5), a prototypical mesogen that is of interest for organic electronics. The thermotropic behavior reveals different mesophases. When cooling down from the isotropic phase, a transition to nematic (≈715 K) is found, then a smectic SA (≈657 K) and another smectic, SXA (≈642 K), before a crystalline phase is recovered (≈617 K). This phase sequence is compared with experimental findings. The different phases are described in terms of their molecular organization, orientational and positional order parameters, and pair distribution functions, as well as of their dynamics properties. In particular, the smectic phases that have not yet been characterized experimentally are discussed. By analyzing the effective shape of P5, it is concluded that its internal torsions and bending make it less rigid than could be expected.

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Liquid crystalline properties of all symmetric p-phenylene and 2,5-thiophene pentamers

Cited by 18 publications

References 16 publications

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

meta-Cybotaxis and nematic biaxiality

Quinquephenyl: The Simplest Rigid‐Rod‐Like Nematic Liquid Crystal, or is it? An Atomistic Simulation

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Liquid crystalline properties of all symmetric p-phenylene and 2,5-thiophene pentamers

Cited by 18 publications

References 16 publications

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C60

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C60

meta-Cybotaxis and nematic biaxiality

Quinquephenyl: The Simplest Rigid‐Rod‐Like Nematic Liquid Crystal, or is it? An Atomistic Simulation

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Product

Resources

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From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀