Designing new lyotropic amphiphilic mesogens to optimize the stability of nematic phases

Boden, N.; Bushby, Richard J.; Ferris, Lori A.; Hardy, Cordell M.; Sixl, F.

doi:10.1080/02678298608086498

Cited by 83 publications

(44 citation statements)

References 39 publications

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“…Such behaviour contradicts the experimental observation as these molecules are soluble in water. 12,16 Therefore, we suggest that the GAFF force field poorly describes this type of system. For TP6EO2M in water, our results show that GAFF potential leads to either, too strong attraction between the chromonic molecules, favouring phase separation over an aligned aggregate, or too weak attraction between EO chains and water, making the molecules hardly soluble.…”

Section: Self-assemblymentioning

confidence: 95%

“…This molecule was designed specifically to form only rod-shaped aggregates in aqueous solutions. 12,13 The mesophases formed by TP6EO2M in water have been extensively studied using proton NMR [12][13][14][15][16] , x-ray diffraction, 12,13 and DSC 14 across a wide range of concentrations and temperatures. In solution the molecules aggregate into small randomly-oriented stacks which, depending on temperature and concentration, self-organize into a variety of ordered phases.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamics of the self-assembly of non-ionic chromonic molecules using atomistic simulations. The case of TP6EO2M in aqueous solution

et al. 2015

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(2015) 'Thermodynamics of the self-assembly of non-ionic chromonic molecules using atomistic simulations.The case of TP6EO2M in aqueous solution.', Soft matter., 11 (4). pp. 680-691. Further information on publisher's website:http://dx.doi.org/10.1039/C4SM02275KPublisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTAtomistic molecular dynamic simulations have been performed for the non-ionic chromonic liquid crystal 2,3,6,7,10,11-hexa-(1,4,7-trioxa-octyl)-triphenylene (TP6EO2M) in aqueous solution. TP6EO2M molecules consist of a central poly-aromatic core (a triphenylene ring) functionalized by six hydrophilic ethyleneoxy (EO) chains, and have a strong tendency to aggregate face-to-face into stacks even in very dilute solution. We have studied self-assembly of the molecules in the low concentration range corresponding to an isotropic solution of aggregates, using two force fields GAFF and OPLS. Our results reveal that the GAFF force field, even though it was successfully used previously for modelling of ionic chromonics, overestimates the attraction of TP6EO2M molecules in water. This results in an aggregation free energy which is too high, a reduced hydration of EO chains and, therefore, molecular self-assembly into compact disordered clusters instead of stacks. In contrast, use of the OPLS force field, leads to self-assembly into ordered stacks in agreement with earlier experimental studies of triphenylene-based chromonics. The free energy of association follows a "quasi-isodesmic" pattern, where the binding free energy of two molecules to form a dimer is of the order of 3 RT larger than the corresponding energy of addition of a molecule into a stack. The obtained value for the binding free energy, ∆ agg G 0 = -12 RT, is found to be in line with the published values for typical ionic chromonics (-7 to -12 RT), and agrees reasonably well with the experimental results for this system. The calculated interlayer distance between the molecules in a stack is 0.37 nm, which is at the top of the range found for typical chromonics (0.33-0.37 nm). We suggest that the relatively large layer spacing can be attributed to the repulsion between EO side chains.2

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Section: Self-assemblymentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Thermodynamics of the self-assembly of non-ionic chromonic molecules using atomistic simulations. The case of TP6EO2M in aqueous solution

et al. 2015

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“…Such a phase has only been found experimentally for mixtures of disklike molecules with strong attractions between their central cores and various (typically) smaller molecules. [49][50][51][52][53] …”

Section: Phase Diagrammentioning

confidence: 99%

Phase behavior of hard colloidal platelets using free energy calculations

Maréchal

Cuetos

Martínez–Haya

et al. 2011

The Journal of Chemical Physics

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We investigate the phase behavior of a model for colloidal hard platelets and rigid discotic molecules: oblate hard spherocylinders (OHSC). We perform free energy calculations using Monte Carlo simulations to map out the phase diagram as a function of the aspect ratio L/D of the particles. The phase diagram displays a stable isotropic phase, a nematic liquid crystal phase for L/D ≤ 0.12, a columnar phase for L/D 0.3, a tilted crystal phase for L 0.45, and an aligned crystal phase for L/D 0.45. We compare the results to the known phase diagram of hard cut spheres. Thin cut spheres are almost cylinder-shaped, while the interactions between real discotic mesogens and colloidal platelets are more consistent with the toroidal rims of the OHSC. Since the shapes of the OHSC and the cut spheres are otherwise similar, the phase diagrams of the two types of particles are quite akin. However, the tilted crystal phase for OHSC, which is of a crystal type that is frequently found in experiments on disklike molecules, has not been found for hard cut spheres. Furthermore, although we have found a cubatic phase, it was shown to be definitely unstable, whereas the stability of the cubatic phase of cut spheres is still disputed. Finally, we also show that the phase boundaries differ significantly from those for cut spheres. These are remarkable consequences of a subtle change in particle shape, which show that for a detailed comparison with the phase behavior of experimental particles, the OHSC should be used as a model particle.

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“…tobacco mosaic virus (TMV) (Bawden et al 1936, Bawden and Pirie 1937, Bernai and Fankuchen 1941, Oster 1950, Kreibig and Wetter 1980, Fraden et al 1985, fd-virus (Lapointe and Marvin 1973, Maret and Dransfeld 1985, Booy and Fowler 1985; (iv) rodlike micelles of amphiphiles (Lawson and Flaut 1967, Radley and Reeves 1975, Yu and Saupe 1980, Hendrikx and Charvolin 1981, Boden et al 1986;…”

Section: Comparison With Experimentsmentioning

confidence: 99%

Phase transitions in lyotropic colloidal and polymer liquid crystals

1992

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An overview is given of theory and experiments on liquid crystal phases which appear in solutions of elongated colloidal particles or stiff polymers. The Onsager (1949) virial theory for the isotropic-nematic transition of thin rodlike particles is treated comprehensively along with extensions to polydisperse solutions and soft interactions. Computer simulations of liquid crystal phases in hard particle fluids are summarized and used to assess the quality of statistical mechanical theories for stiff particles at higher volume fraction-like the inclusion of higher virial coefficients, y-expansion, scaled particle theory and density functional theory. Both computer simulations and density functional theory indicate formation of more highly ordered smectic phases. The range of experimental applicability is strongly widened by the extension of the virial theory to wormlike chains by Khokhlov andSemenov (1981, 1982). Finally, experimental results for a number of carefully studied, charged and uncharged colloids and polymers are summarized and compared to theoretical results. In many cases the agreement is semi-quantitative.

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Designing new lyotropic amphiphilic mesogens to optimize the stability of nematic phases

Cited by 83 publications

References 39 publications

Thermodynamics of the self-assembly of non-ionic chromonic molecules using atomistic simulations. The case of TP6EO2M in aqueous solution

Thermodynamics of the self-assembly of non-ionic chromonic molecules using atomistic simulations. The case of TP6EO2M in aqueous solution

Phase behavior of hard colloidal platelets using free energy calculations

Phase transitions in lyotropic colloidal and polymer liquid crystals

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