Dielectric relaxation and the mobility of mesogenic groups in cholesterol-containing liquid crystalline polymers containing spacers of various lengthsстатья
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Дата последнего поиска статьи во внешних источниках: 29 апреля 2021 г.
Аннотация:Dielectric relaxation processes occurring in LC polymers containing mesogenic cholesterol groups in the side chains have been investigated within the temperature range from −170–+230°C and in the frequency range from 0.06–1000 kHz. At low temperatures it was found that for all the polymers under study there are three regions in which tan δ goes through a maximum, and these regions are assigned to local forms of motion of two COO groups in side chains. At high temperatures the dielectric loss region that is not frequency dependent determines the temperature of transition to the isotropic state. The two relaxation processes detected in the region of the mesomorphic state near the glass transition temperature Tg have high activation energy values, and structural transitions were observed. Possible mechanisms of these phenomena are discussed.