The preparation of star polymers bearing seven linear poly(ε-caprolactone) arms linked to a β-cyclodextrin (β-CD) core is described. The hydroxyl groups at C6 of β-CD were selectively protected with a tert-butyldimethylsilyl (TBDMS) group, and then the remaining hydroxyl groups at C2 and C3 were subsituted with a benzyloxy group. The TBDMS groups were removed to give a cyclodextrin derivative 3 with seven free primary hydroxyl groups. The controlled ring-opening polymerization of ε-caprolactone (ε-CL) was carried out using the multifunctional initiator 3 with stannous octoate (Sn(Oct)2) as the catalyst to obtain a star-shaped poly(ε-CL) (4). After the polymerization proceeded sufficiently, the addition of another portion of ε-CL to the system afforded 4 with longer arm length. Debenzylation of 4 was successfully achieved by catalytic hydrogenolysis on Pd(OH)2/C to produce a star-shaped poly(ε-CL) with a hydrophilic moiety of β-CD as the core.
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