Organic-inorganic hybrid brushes comprised of macrocyclic oligomeric silsesquioxane (MOSS) and poly(epsilon-caprolactone) (PCL) were synthesized via the ring-opening polymerization of epsilon-caprolactone (CL) with cis-hexa[(phenyl) (2-hydroxy-ethylthioethyldimethylsiloxy)]cyclohexasiloxane as the initiator The MOSS macromer bearing hydroxyl groups was synthesized via the thiol-ene radical addition reaction between cis-hexa[(phenyl)(vinyldimethylsiloxy)]cyclohexasiloxane and beta-mercaptoethanol. The organic-inorganic PCL cyclic brushes were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). These MOSS-PCL, brushes were then used to prepare the supramolecular inclusion complexes with alpha-cyclodextrin (alpha-CD). The X-ray diffraction (XRD) indicates that the organic-inorganic inclusion complexes (ICs) have a channel-type crystalline structure. It is noted that the molar ratios of CL unit to alpha-CD for the organic-inorganic ICs are quite dependent on the lengths of the PCL chains bonded to the silsesquioxane macrocycle. While the PCL chains were short, the efficiency of inclusion complexation was significantly decreased. The decreased efficiency could be attributed to the repulsion of the adjacent PCL chains bonded to the silsesquioxane macrocycle and the restriction of the bulky silsesquioxane macrocycle oil the motion of PCL chains; this effect is pronounced with decreasing the length of the PCL chains. (C) 2009 Wiley Periodicals. Inc. J Polym Sci Part A. Polym Chem 47. 6894-6907, 2009