Supramolecular Inclusion Complexes of a Star Polymer Containing Cholesterol End-Capped Poly(?-caprolactone) Arms with ?-Cyclodextrin

Abstract

A novel hexa-armed and star-shaped polymer containing cholesterol end-capped poly(epsilon-caprolactone) arms emanating from a phosphazene core (N3P3-(PCL-Chol)(6)) was synthesized by a combination of ring-opening polymerization and click chemistry techniques. For this purpose, the terminal OH groups of the synthesized precursor (N3P3-(PCL-OH)(6)) were converted into -Chol through a series of reaction. Both N3P3-(PCL-OH)(6) and N3P3-(PCL-Chol)(6) were then employed in the preparation of supramolecular inclusion complexes (ICs) with -cyclodextrin (-CD). The latter formed ICs with -CD in higher yield. The host-guest stoichiometry (epsilon-CL:-CD, mol:mol) in the ICs of N3P3-(PCL-Chol)(6) was found to be 1.2. The formation of supramolecular ICs of N3P3-(PCL-Chol)(6) with -CD was confirmed by using Fourier transform infrared (FTIR) and H-1 nuclear magnetic resonance (NMR) spectroscopic methods, wide-angle X-ray diffraction (WAXD), and thermal analysis techniques. WAXD data showed that the obtained ICs with N3P3-(PCL-Chol)(6) had a channel-type crystalline structure, indicating the suppression of the original crystallization of N3P3-(PCL-Chol)(6) in -CD cavities. Moreover, the thermal stabilities of ICs were found to be higher than those of the free star polymer and -CD. Furthermore, the surface properties of N3P3-(PCL-Chol)(6) and its ICs with -CD were investigated by static contact angle measurements. The obtained results proved that the wettability of N3P3-(PCL-Chol)(6) successfully increased with the formation of its ICs with -CD. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3406-3420