Bent-shaped liquid crystal dimers. Influence of the direction of the oxybiphenylenecarboxyl groups on their mesomorphic behavior

Abstract

In order to study what role the direction of the whole mesogenic groups play on their mesomorphic behavior we synthesized a series of bent-shaped dimers in which the mesogens differ in their relative orientation along the long molecular axis of the dimers. A tilted anticlinic smectic mesophase is presented exclusively by the dimer where the mesogens are tethered in a head-to-head fashion. The head-to-tail and tail-to-tail organizations of the mesogens preclude any kind of mesophase formation. The mesomorphic behavior of dimers was characterized by a combination of polarizing optical microscopy, differential scanning calorimetry and computational techniques.

Diphenylanthrylene and diphenylfluorene-based segmented conjugated polymer films as fluorescent chemosensors for nitroaromatics in aqueous solution

“…The films were casted onto carefully leveled quartz, glass, dodecyltrichlorosilane (DTS)-coated glass or polymeric substrates (2.4 cm × 0.8 cm) by spreading over the whole area 0.1 ml of a chloroform solution of the NAC which was first allowed to evaporate slowly in a nitrogen filled chamber and was then kept under vacuum for 12 h at room temperature. We have previously reported the preparation of (DTS)-coated glass substrates by treating the glass substrates first with piranha solution (70% H 2 SO 4 , 30% H 2 O 2 ) and then with DTS in CH 2 Cl 2 [28]. The thickness of cast films was measured in at least five different regions via a UV-visible interferometer (Model F20; Filmetrics, Inc.) operated in reflectance mode with a spot size of ∼0.5 mm.…”