Abstract: Highly expandable materials have been developed for filling an aneurysm sac and for sealing of endoluminal devices vessel walls. The expandable materials have appropriate chemical and physical properties to withstand radiation, sterilization, or storage in sterilizing solution, without loss of expandable characteristics. The expandable materials may contain protectants, prophylactic, diagnostic, therapeutic, or imaging agents. The expandable materials form a seal that actively conforms to vascular anatomy sealing any leaks that may occur after device implantation. In one embodiment, the technology is used to prevent leaks associated with abdominal aortic aneurysm (AAA) repair, especially for complex AAA repair.