On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

Abstract

Abstract.We investigate the influence of transient or permanent elasticity on liquid phases with octupolar (tetrahedral) order, a question that has never been addressed before. The focus will be on optically isotropic liquid phases with tetrahedral order including the T d phase and the chiral T phase introduced by Fel. It turns out that the presence of both, a network as well as tetrahedral order can lead to the formation of chiral domains of both hands in an optically isotropic fluid due to a completely novel mechanism, thus providing a possible macroscopic explanation for recent experimental observations. We study in detail how elasticity influences the macroscopic dynamics of both, the T d and the T phase. The simultaneous presence of a transient network as well as of octupolar order is shown to lead to completely new crosscoupling phenomena for optically isotropic systems including transient dissipative elastic strains due to temperature gradients.

Spontaneous mirror symmetry breaking in benzil-based soft crystalline, cubic liquid crystalline and isotropic liquid phases

“…With further decrease in the temperature the number of linkages between the clusters increases. Mirror symmetry breaking sets in at the next much sharper transition at 128 °C which we attribute to the transition from the cybotactic to a percolated liquid, after crossing a certain critical density of connectivity between the cybotactic clusters, 6a , 32 thus leading to a long range transmission of the helical twist, and hence, chirality (Iso 1 [ * ] ). In the Iso 1 [ * ] range the connections are transient and at the next transition at 122 °C they become permanent with formation of the Ia 3[combining macron] d phase (or I 23 [ * ] for the shorter homologues, Fig.…”

Dynamic interplay of nematic, magnetic, and tetrahedral order in ferromagnetic nematic phases

“…As a consequence, the ground state might not be homogeneous, resembling the case of added chirality to nematic liquid crystals. In fact these terms are well-known by now to give rise to ambidextrous helicity [14,15,31,32]. In case one can obtain sufficiently large domains of either hand in a ferromagnetic nematic liquid crystal composed of nonchiral constituents, this would form a rather obvious evidence of the presence of tetrahedral order.…”

“…In addition, there were experimental reports indicating the presence of tetrahedral order in another class of compounds, namely ferrocenomesogens [29,30]. Most of these observations and experimental results such as ambidextrous helicity and ambidextrous chirality [16,19,26] and unusual behavior near the isotropic -liquid crystal phase transitions including shifts of the phase transition temperature by up to 10 K linear in electric fields, two optically isotropic phases in magnetic fields and reentrant isotropic phases [17,18,20,23,25,27,28] could be interpreted successully in terms of the occurrence of tetrahedral order [12,14,15,31,32]. In parallel tetrahedral order has been incorporated in the dynamic description of movable and deformable active particles which are used as models for self-propelled microorganisms in biological applications [33][34][35].…”

“…Quite recently there is also growing interest in clarifying various mathematical aspects of tetrahedral order in two and three spatial dimensions [36][37][38]. Last year it has been pointed out [31] that the observed macroscopic chiral * tilen.potisk@uni-bayreuth.de domains in optically isotropic partially fluid systems [39][40][41] can be interpreted naturally in terms of tetrahedral order provided a transient network is assumed. For a recent review of tetrahedral order in liquid crystals we refer to [32].…”

Dissipative versus reversible contributions to macroscopic dynamics: the role of time-reversal symmetry and entropy production

“…Since leftand right-handed helices are equally likely, this is called ambidextrous helicity. Such a phenomenon can even occur in an optically isotropic system, when tetrahedral order is combined with transient elasticity (Brand and Pleiner 2017).…”