Sliding graft copolymer (SGC) is a polyrotaxane (PR) composed of a poly(ethyelene glycol) (PEG) axle and α-cyclodextrins (α-CDs) substituted with polymer graft-chains. We have previously reported a sharp-endothermic phase transition of SGCs, which was expected due to the high mobility of graft chains by the mechanical linkage of PRs. To examine this hypothesis, SGCs with well-defined structures were prepared. PRs consisting of monoazidated α-CD and PEG were grafted with monomethoxy poly(ethylene glycos)s (mPEGs) via click chemistry. The SGC bearing shortest graft chains (mPEG750) did not exhibit endotherm, whereas those with side chains of mPEG2000 and mPEG4000 underwent endothermic phase transition. However, values of the transition temperatures and those of melting enthalpies were lower than those of unmodified mPEGs. Unlike our previous report, the SGCs synthesized here contained densely-packed α-CDs, which were capable of rotational movement but not translational movement. The endothermic peak observed for the present SGC is relatively broader than that observed for our previous SGC, which suggests that the mobility of α-CDs were critical to induce sharp-endothermic phase transition. Display omitted •Sliding graft copolymers with different side chain lengths were synthesized.•The copolymer endotherm temperatures were lower than those of side chain polymers.•The limited motion of side chain grafted rings lowered the copolymer endotherms.