Dielectric relaxation of liquid-crystalline polyrotaxane

A new supramolecular system, liquid-crystalline polyrotaxane (LCPR), has been recently prepared by introduction of 4-cyano-4′-n-pentylbiphenyl (5CB) groups to the cyclic molecules of a polyrotaxane (PR) consisting of polyethylene glycol (PEG) and α-cyclodextrin (α-CD). Here we measured and compared the dielectric relaxations of PR and LCPR in solid state to investigate molecular motions of α-CD in PR and LCPR. It was found that PR exhibited a single relaxation mode while LCPR had two modes. These results suggested that the relaxation mode in PR would be due to the sliding fluctuation of α-CD along the axis chain and that the other mode in LCPR should arise from the rotational fluctuation of α-CD modified by 5CB.