in which an n octyl group was introduced into a cyclic molecule was prepared in the same manner as in preparation example 1 except that 4 17 g of n butyl isocyanate was changed to 10 9 g of n octyl isocyanate the introduction rate of the n octyl group in the polyrotaxane pr 5 was 47 part of the reaction solution obtained in preparation example 2 was taken out purified using methanol and acetone in the same manner as in preparation example 2 and dried the resulting polyrotaxane had an introduction rate of an n butyl group of 48 the remaining reaction solution was blended with 50 mg of dibutylhydroxytoluene and stirred at 25 u00b0 c for 15 minutes for dissolution of dibutylhydroxytoluene the resulting solution was then blended with 10 5 g of 2 methacryloyloxyethyl isocyanate stirred at 25 u00b0 c for 30 minutes warmed to 60 u00b0 c and reacted at that temperature for four hours the resulting reaction solution was cooled to 25 u00b0 c added to a large amount of methanol and stirred and subjected to centrifugation for recovery of a precipitate the obtained precipitate was dissolved in a large amount of acetone added to a large amount of methanol and stirred to be precipitated again and subjected to centrifugation for recovery of the precipitate the obtained precipitate was dried to give 115 3 g of polyrotaxane pr 6 in which an n butyl group and a methacryloyl group were introduced into a cyclic molecule the introduction rate of the n butyl group in the polyrotaxane pr 6 was 48 as mentioned above and the introduction rate of the methacryloyl.