Dynamics of polyrotaxane investigated by neutron spin echo

摘要

The dynamics of a molecular necklace known as polyrotaxane (PR), in which alpha-cyclodextrins (CDs) are threaded into a poly (ethylene glycol) (PEG) chain, was investigated by means of neutron spin echo (NSE) measurements. We observed that threading CDs into PEG slowed down the local dynamics and changed its Q-dependence. A solution of PEG in DMSO-d(6) showed a dynamical crossover from collective diffusion dynamics to the Zimm mode, just as in conventional polymer solutions; however, the motion of PR in DMSO-d(6) was diffusive for the whole Q range. This may be because the persistence length l(p) of PR was much larger than that of PEG and was similar to the mesh size of PR. The diffusive mode in a high Q regime, corresponding to a length scale of less than the l(p) value of PP, contained the mode of the sliding of CDs along a rod-like PEG segment in one dimension.