Biodegradable poly(l-lactide)-grafted α-cyclodextrin copolymer displaying specific dye absorption by host-guest interactions

A biodegradable graft copolymer (CD-g-PLLA) composed of α-cyclodextrin (α-CD) and poly(l-lactide) (PLLA) was synthesized by the ring-opening polymerization of L-LA using mostly trimethylsilylated α-CD (TMS-α-CD) as an initiator. TEM measurements of the CD-g-PLLA film showed a nanoscale lamellar-type microphase-separated structure in the most of the film. In contrast, an irregular phase-separated structure was observed in the TMS-CD-g-PLLA film, suggesting that the hydroxyl groups in CD-g-PLLA governed the formation of the lamellar structure, likely because of their important roles in intra- and/or intermolecular hydrogen bonding. The CD-g-PLLA film was mechanically tenacious but soft, and it showed reduced PLLA crystallinity, high transparency, and accelerated hydrolytic degradation. The CD-g-PLLA film served as a host for various dye compounds based on specific host-guest interactions of the α-CDs.