144 research outputs found
Intercalated soft-crystalline mesophase exhibited by an unsymmetrical twist-bend nematogen
A number of new states of matter have been reported in recent years for liquid crystal dimers, most notably the twist-bend nematic phase which exhibits spontaneous breaking of symmetry through the emergence of chiral structures in an achiral fluid. In this communication we report on an unsymmetrical liquid crystal dimer that exhibits a transition from the spontaneously chiral twist-bend nematic phase into a novel smectic liquid crystal phase
Progression from nano to macro science in soft matter systems: : dimers to trimers and oligomers in twist-bend liquid crystals
In this article we report on the characterization and properties of several unsymmetrical phenyl-benzoate bimesogens that exhibit the soft-matter, twist-bend nematic (NTB) phase. We use this study as a basis to examine the phase behaviour of associated novel trimeric and tetrameric materials, in order to investigate the potential for oligomeric materials to form the NTB phase. Based on our results we hypothesise that higher oligomers and even polymers are highly likely to exhibit the NTB phase, provided they retain a gross bent structure between consecutive mesogenic units. Thus we show at the level of nanoscale organization, dimers can template with respect to one another to form mesophases that are also found in macromolecular systems
Order Parameters, Orientational Distribution Functions and Heliconical Tilt Angles of Oligomeric Liquid Crystals
We
compare the order parameters, orientational distribution functions (ODF) and
heliconical tilt angles of the TB phase exhibited by a liquid-crystalline dimer
(CB7CB) to a tetramer (O47) and hexamer (O67) by SAXS/WAXS. Following the N-TB
phase transition we find that all order parameters decrease, and while â©P2 âȘ remains positive â©P4 âȘ becomes negative. For all three materials the
order parameter â©P6 âȘ is near zero in both phases. The ODF is
sugarloaf-like in the nematic phase and volcano-like in the TB phase, allowing
us to estimate the heliconical tilt angle of each material and its thermal
evolution. The heliconical tilt angle appears to be largely
independent of the material studied despite the differing number of mesogenic
units
An interplay between molecular pairing, smectic layer spacing, dielectric anisotropy and re-entrant phenomena in Ï-alkenyloxy cyanobiphenyls
âThrough My Dreamâ: Trevor Joyceâs Translations
Almost all Irish translators work with what Lawrence Venuti calls a âdomesticatingâ model of recreating a translated poem as if it had been originally written in the target language. However, some of the most important Irish translators of the past, notably James Clarence Mangan and Brian Coffey, have used what Venuti terms a âforeignizingâ strategy which, on the contrary, highlights the difficulties and resistances of the source text to transparent re-presentation. The two approaches roughly correspond to two modes of translation evident in the work of the most influential anglophone poetry translator of the early twentieth century, Ezra Pound. In his translation of the Buile Suibhne as the Poems of Sweeny Peregrine (1976), which cites Poundian precedent, the contemporary Irish neo-modernist poet Trevor Joyce (b. 1947) uses both modes to produce a destabilised, postmodern âworkingâ which exploits the originalâs gaps, scribal interpolations and narrative contradictions, as well as poignantly rendering its expressivist lyrics. Radical translation strategies can be seen to inform other aspects of Joyceâs work, from his use of Japanese and Chinese forms and materials in Stone Floods (1995), to cut-up and collage in Trem Neul (2000), and from folk-song and poetry from the Finno-Ugric, Hungarian and Irish in Whatâs in Store (2007) and Courts of Air and Earth (2008) to, most recently, the unpublished Romeâs Wreck, which âtranslatesâ Edmund Spenserâs âThe Ruines of Romeâ (1591) âintralinguallyâ, to use Roman Jakobsonâs term, that is, from one form of English into another.Presque tous les traducteurs irlandais travaillent Ă partir dâun modĂšle que Lawrence Venuti appelle « domesticating translation ». Ils tentent de recrĂ©er le poĂšme comme sâil avait Ă©tĂ© Ă©crit dans la langue cible. Cependant, certains parmi les plus grands traducteurs irlandais du passĂ©, notamment James Clarence Mangan et Brian Coffey, ont utilisĂ© une stratĂ©gie que Venuti appelle « foreignizing translation » qui, Ă lâopposĂ©, souligne les difficultĂ©s et les rĂ©sistances que le texte source oppose Ă une reprĂ©sentation transparente dans le texte cible. Ces deux approches correspondent en gros Ă deux modes de traduction visibles dans le travail dâEzra Pound, le poĂšte-traducteur anglophone qui a exercĂ© le plus dâinfluence au dĂ©but du xxe siĂšcle. Dans sa traduction de Buile Suibhne, The Poems of Sweeny Peregrine (1976), qui cite le prĂ©cĂ©dent poundien, le poĂšte neo-moderniste irlandais Trevor Joyce (nĂ© en 1947) se sert des deux modes pour produire une version dĂ©stabilisĂ©e et postmoderne du texte source, qui exploite les blancs, les interpolations du scribe et les contradictions narratives, tout en traduisant de maniĂšre intense lâexpressivisme de lâoriginal. Des stratĂ©gies radicales de traduction ont Ă©galement influencĂ© dâautres aspects du travail de Joyce, de son utilisation de formes et de sources japonaises et chinoises dans Stone Floods (1995) Ă sa technique du coupĂ©-collĂ© dans Trem Naul (2000), et de son utilisation du chant folklorique et de la poĂ©sie dâorigine finno-ougrienne, hongroise et irlandaise dans Whatâs in Store (2007) et Courts of Air and Earth (2008) Ă son travail rĂ©cent Romeâs Wreck (non encore publiĂ©) qui « traduit » « The Ruines of Rome » (1591) dâEdmund Spenser de façon âintralingualeâ (terminologie de Roman Jakobson), câest Ă dire dâune forme de la langue anglaise vers une autre
Molecular shape as a means to control the incidence of the nanostructured twist bend phase
Liquid crystalline phases with a spontaneous twist-bend modulation are most commonly observed for dimers and bimesogens with nonamethylene spacers. In order to redress this balance we devised a simple chemical intermediate that can be used to prepare unsymmetrical bimesogens; as a proof of concept we prepared and studied eleven novel materials with all found to exhibit the twist-bend phase and exhibit a linear relationship between TN-I and TTB-N. A computational study of the conformational landscape reveals the octamethyleneoxy spacer to have a broader distribution of bend-angles than the nonamethylene equivalent, leading to reductions in the thermal stability of the TB phase. This result indicates that a tight distribution of bend-angles should stabilise the TB phase and lead to direct TB-Iso phase transitions, and conversely a broader distribution should destabilise the TB phase which may allow new states of matter that are occluded by the incidence of this phase to be revealed
An experimental and computational study of calamitic and bimesogenic liquid crystals incorporating an optically active [2,2]-paracyclophane
Two liquid-crystalline materials containing an optically active (R)-4-hydroxy-[2,2]-paracyclophane group were prepared, one in which the chiral group is a bulky terminal unit and one in which it forms part of a terphenyl-like mesogenic unit. Both materials exhibit monotropic chiral nematic phases. Partial phase diagrams were constructed for mixtures of both materials with 5CB, allowing us to extrapolate pitch lengths and helical twisting power values (HTP) for each material. The HTP value of the material with a âlockedâ paracyclophane is 70% higher than that of a âfreeâ paracyclophane and this is rationalised as being due to the reduction in conformational freedom of the former material relative to the later
A Nematic to Nematic Transformation Exhibited by a Rod-Like Liquid Crystal
A novel, highly polar rod-like liquid crystal was found to exhibit two distinct nematic mesophases (N and Nx). When studied by microscopy and X-ray scattering experiments, and under applied electric fields, the nematic phases are practically identical. However, calorimetry experiments refute the possibility of an intervening smectic mesophase, and the transformation between the nematic phases was associated with a weak thermal event. Analysis of measured dielectric data, along with molecular properties obtained from DFT calculations, applying the Maier-Meier relationship allowed for the degree of antiparallel pairing of dipoles in both nematic phases to be quantified. Based on the results, we conclude that the onset of the lower temperature phase is driven by the formation of antiparallel molecular associations
Evaluation of 4-alkoxy-40-nitrobiphenyl liquid crystals for use in next generation scattering LCDs
We have prepared nine members of the 4-alkoxy-40-nitrobiphenyl family of liquid crystals and evaluated their thermal behaviour by a combination of polarised optical microscopy, differential scanning calorimetry and small angle X-ray scattering, as well as in single pixel scattering devices for use in backlight free liquid crystal displays (LCDs). Whereas homologues with shorter terminal aliphatic chains are nematogenic, those with longer aliphatic chain lengths exhibit an additional smectic A phase, identified as the subtype SmAD by SAXS with all materials having a D/L ratio (smectic layer spacing divided by molecular length) of 1.4. When doped with 0.1 wt% hexadecyltrimethylammonium perchlorate we observed that the SmAD phase of compound 9 could be switched with a relatively low voltage (58 VRMS, roughly half that required for the analogous nitrile). This apparent reduction in threshold voltage, which occurs as a consequence of switching from a nitrile- to a nitro- group, provides a new impetus to study alternative polar terminal groups when designing host materials for smectic A scattering devices
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