Physical properties and enzymatic hydrolysis of poly( L ‐lactide)–TiO 2 composites

Amorphous poly( L ‐lactide) (PLLA) composite films with titanium dioxide (TiO 2 ) particles were prepared by solution‐casting using methylene chloride as a solvent, followed by quenching from the melt. The effects of surface treatment, volume fraction, size, and crystalline type of the TiO 2 particles on the mechanical properties and enzymatic hydrolysis of the composite films were investigated. The tensile strength of the PLLA composite films containing TiO 2 particles except for anatase‐type ones with a mean particle size of 0.3–0.5 μm was lowered and the Young's modulus became higher with increasing the content of TiO 2 particles. The tensile strength of the composite films containing anatase‐type TiO 2 with a mean particle size of 0.3–0.5 μm at contents of 20 wt % or less was almost the same as that of the pure PLLA film. The enzymatic hydrolysis of PLLA matrix was accelerated by the addition of the hydrophilic anatase‐type TiO 2 particles (nontreated or Al 2 O 3 treated) with a mean particle size of 0.3–0.5 μm at relatively high contents such as 20 wt %. On the other hand, the enzymatic hydrolysis of PLLA matrix was inhibited by composite formation with the hydrophobic rutile‐type TiO 2 particles (Al 2 O 3 ‐stearic acid treated, or ZrO 2 ‐Al 2 O 3 ‐stearic acid treated). These results suggest that the mechanical properties and enzymatic hydrolyzability of the PLLA can be controlled by the kind and amount of the added TiO 2 particles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 190–199, 2005