Switching of polymerization activity of cinnamoyl-α-cyclodextrin

Abstract

Cinnamoyl α-cyclodextrin (α-CD) has been found to initiate polymerization of δ-valerolactone (δ-VL) to give a polymer in high yield. By the presence of the cinnamoyl group, hydrogen bond was formed between the carbonyl oxygen of δ-VL and the hydroxyl group of CD to activate the monomer, which was observed by FT-IR measurements. However, the cinnamoyl group at the C₃- and C₆-positions of α-CD did not affect the polymerization ability. Only that of the C₂-position showed high polymerization activity. The polymerization activity could be switched by the photoisomerization of the cinnamoyl group attached to the rim of α-CD. Specific monomer recognition and polymerization in the active site of the α-CD cavity was changed by the photoisomerization.