The phase transition behavior of the liquid crystal dimer α,ω-bis(4,4'-cyanobiphenyl)nonane (CBC9CB), which has been reported to exhibit a nematic-nematic phase transition, has been investigated by means of high-resolution adiabatic scanning calorimetry. This nematic-nematic phase transition is weakly first-order with a latent heat of 0.24±0.01 kJ kg(-1). Mixtures up to 40 wt % with 4-pentyl-4'-cyanobiphenyl (5CB) liquid crystals have also been investigated, which also show this nematic to nematic phase transition. The transition stays weakly first-order with a decreasing latent heat with increasing concentration of 5CB. For mixtures with more than 40 wt % uniaxial nematic-unknown nematic phase transition was not observed.

It is demonstrated that interactions between nanoparticles and topological defects induce a twist-grain boundary phase in a chiral liquid crystal. The occurrence of this phase, the analogue of the Shubnikov phase in type-II superconductors, is driven by direct interactions between surface-functionalized CdSe quantum dots and screw dislocations. It is shown that, within an adaptive-defect-core-targeting mechanism, nanoparticles of appropriate size and functionalization adapt to qualitatively different cores of topological defects such as disclination lines and screw dislocations. This mechanism enables the effective reduction of the energetically costly, singular defect core volume, while the surrounding phase ordering remains relatively weakly affected. The findings suggest new pathways towards the controlled assembly of superstructures in diverse, symmetry-broken, condensed-matter systems, ranging from nanoparticle-decorated liquid crystals to superconductors.

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A detailed study has been performed for mixtures of octyloxycyanobiphenyl (8OCB) and nonyloxycyanobiphenyl (9OCB) liquid crystals and nine of their mixtures by means of high-resolution adiabatic scanning calorimetry. The isotropic to nematic transitions are weakly first order with latent heat values in the range usually encountered for this transition in other liquid crystals. With the exception of pure 8OCB, for which only an upper limit of 1.8 J  kg(-1) for the latent heat could be established, finite latent heats have been obtained for the nematic to smectic-A transition of all the mixtures and of pure 9OCB. The concentration dependence of their latent heats could be well fitted with a crossover function consistent with a mean-field free-energy expression that has a nonzero cubic term induced by the Halperin-Lubensky-Ma (HLM) coupling between the smectic-A order parameter and the orientational director fluctuations. Clearly first-order transitions with measurable latent heats are found for mole fractions of 9OCB in the mixtures where the effective critical exponent for the specific-heat capacity has substantially lower values than the tricritical one (0.5). This is qualitatively different from what has been observed so far in other liquid-crystal systems and yields strong experimental evidence from a calorimetric experiment for the HLM coupling between the smectic-A order parameter and the director orientation fluctuations.