Low‐molecular‐weight copolymers composed of <scp>L</scp>‐lactic acid and various <scp>DL</scp>‐hydroxy acids as biodegradable carriers

Abstract

Abstract Biodegradable copolymers of L ‐lactic acid ( L ‐LA) and DL ‐α‐hydroxy acids with relatively low molecular weights, for example L ‐LA/ DL ‐lactic acid ( DL ‐LA), L ‐LA/ DL ‐α‐hydroxybutyric acid ( DL ‐HBA), L ‐LA/ DL ‐α‐hydroxyisovaleric acid ( DL ‐HIVA), and L ‐LA/ DL ‐α‐hydroxyisocaproic acid ( DL ‐HICA), were synthesized by quantitative direct copolycondensation without catalysts at 200°C. The in vitro degradation, which was evaluated by measuring the weight loss of these copolymers in M/15 phosphate buffer solution (pH 7,2) without enzymes at 37°C, is strongly dependent on the kind and molecular weight of these copolymers, resulting in the formation of different degradation patterns such as parabola type ( L ‐LA/ DL ‐HBA system), linear type ( L ‐LA/ DL ‐LA system), and S type ( L ‐LA/ DL ‐HIVA and L ‐LA/ DL ‐HICA systems).