Exhibition of Soft and Tenacious Characteristics Based on Liquid Crystal Formation by Introduction of Cholesterol Groups on Biodegradable Lactide Copolymer

Cholesterol side-functionalized poly(depsipeptide- co- dl-lactide) (PGD- dl-LA-(cholesterol) n ) and poly(depsipeptide) (PGD-(cholesterol) n) were prepared as novel biodegradable liquid crystalline (LC) polymers. These polymer films exhibited different LC phases depending on the cholesterol unit content in the polymers. The thermodynamic stability of these LC phases was quite high, and PGD-(cholesterol) n film exhibited continuous LC phases up to 202 degrees C. The resulting cholesterol LC phases were indicated to act as physical cross-linking points to form noncovalent network structures among the polymer chains. Therefore, PGD- dl-LA-(cholesterol) n film exhibited a rubbery and stretchy nature at 37 degrees C due to physical cross-linking points based on cholesterol LC phase well-dispersed in the film. The cholesterol side-group effects leading to rubbery character and hydrolytic resistance reported herein are rather unique. The biodegradable LC material exhibiting a soft and tenacious nature is a promising candidate for a new class of implant biomaterials used with dynamic organs of the body such as the heart and blood vessels.