Inclusion complexes of alpha-cyclodextrin and (AB)(n) block copolymers

Cyclodextrins thread onto polymer chains to form inclusion complexes, espec ially when the polymer is hydrophobic relative to the solvent. Selective th reading might occur when the polymer architecture contains both hydrophobic and hydrophilic segments. alpha -Cyclodextrin formed crystalline inclusion complexes with (AB)(n) microblock copolymers, where the A block was a line ar alkyl segment containing a single double bond and the B block was an exa ct length segment of poly(ethylene oxide). The complexes were isolated and characterized by solution and solid-state NMR, X-ray diffraction, different ial scanning calorimetry, and thermogravimetric analysis. Each method confi rmed complex formation and showed that the physical properties of the compl exes were distinct from those of its individual components. The X-ray data were consistent with known inclusion complexes having a channel or column c rystal structure. The stoichiometry of the complex formation, 2.3 alpha -cy clodextrin rings per polymer repeat unit, was determined by NMR analysis of the complexes and from an analysis of the inclusion complex yields. The da ta suggest that the inclusion complex stoichiometry is defined by the incre asing insolubility of the polymer-cyclodextrin complex. Solid-state NMR dat a were consistent with a preference for threading onto hydrophobic segments of the (AB)(n) polymer. (C) 2001 John Wiley & Sons, Inc.