Dielectric spectroscopy on liquid‐crystalline main chain polymers with crossing mesogens

A newly synthesized series of liquid‐crystalline main chain polymers with crossing mesogens is investigated using dielectric spectroscopy. The crossing mesogenic units are endowed with hexyl as well as with CN‐wing groups. We examined the change of mobility of these crossing segments with increasing spacer length in the main chain, the relaxation behaviour at the phase transition nematic‐isotropic and the temperature dependence of the absorption intensity. The main results are: there is an alternation of the dielectric relaxation times with respect to the length of the spacer in such a way that the molecular mobility is raised in case of an odd number of methylene groups in the spacer. The steps in the relaxation frequencies at the clearing temperatures are obviously due to a change in the short‐range order caused by the formation of the nematic structure. Owing to a strong dipol‐dipol interaction between neighbouring segments, a decrease of the absorption intensity with decreasing temperature was observed. Furthermore, apart from the low‐frequency absorption a high‐frequency relaxation process could be monitored.