Two kinds of inclusion complexes based on poly(propylene oxide) and β-cyclodextrin

It was shown that depending on the phase state of a polymer guest, poly(propylene oxide), two kinds of inclusion complexes with β-cyclodextrin may be prepared. In a homogeneous solution, complex A is obtained, while in the case of emulsion, complex B is synthesized. The compositions of both complexes are independent of the molecular mass of the polymer and correspond to a molar ratio of β-cyclodextrin: poly(propylene oxide) repeat unit: H2O = 1:2:n. The number of water molecules n is 6 and 2 for complexes A and B, respectively. According to X-ray data, complex A has a crystalline structure composed of monoclinic crystals. Complex B forms a columnar mesophase with the hexagonal arrangement of cyclodextrin columns in the base plane. It was discovered that the studied complexes are capable of mutual transitions: upon the annealing of A complexes, a crystal-mesomorphic structure transition takes place simultaneously with the loss of water. The addition of water to the mesomorphic complex B and the subsequent prolonged stirring of a suspension at 5°C are accompanied by the formation of a monoclinic crystalline structure.