Distinct layered structure with density modulation in solid phase formed from B2 phase of banana molecules

Microbeam resonant x-ray scattering from bromine-substituted bent-core liquid crystals

We studied the local layer structure in the B2 phase of bromine-substituted bent-core liquid crystals in the cell geometry using microbeam resonant x-ray scattering. In the homochiral state of B2 phase, the 3/2 order satellite peak was observed only when the incident x-ray energy is at the K absorption edge of bromine. This result clearly indicates that the B2 homochiral domain forms two-layer superlattice in adjacent layers, the same as in the rodlike Sm-C(A) phase. The work reports on microbeam resonant x-ray scattering experiment from the local layer of the bent-core liquid crystal in the device geometry. Moreover, we can say that bromine is also useful for the analysis of the superstructure of soft materials using resonant x-ray scattering.

Structural study of a bent-core liquid crystal showing the B1-B2 transition

An experimental study of the B1-B2 transition is carried out in a bent-core liquid crystal. The study is essentially based on x-ray measurements as a function of temperature. The B1-B2 transition is extremely unusual and implies a deep structural change from a columnar phase to a lamellar phase. We have found that the B1 phase in our compound is similar to the so-called B1 reversed phase, with an additional splay of the polarization in the columns. On approaching the B2 phase the width of the cross section of the columns increases. The transition is clearly first order, with a large hysteresis though the enthalpy content is very small. A possible mechanism for the transition is briefly sketched.