It has been disclosed for the first time that a cyclodextrin (CD) derivative is able to act as a microcyclic monomer for ring-opening polymerization to produce linear polyglucan. O-Permethylated alpha-, beta-, and gamma -CDs were found to be polymerizable with the aid of a cationic initiator, e.g., Et3O+PF6- in dichloromethane. Interestingly, the more strained monomer (alpha- > beta- > gamma -CD) was less reactive, which is ascribable to the characteristic shape of the CD molecule.