Synthesis and Characterization of Shape Memory Polymer Foams with Improved Mechanical Properties

Abstract

Vascular aneurysms are a significant source of morbidity and mortality, affecting 3 to 5 million Americans annually. Current treatments often require either highly invasive strategies to surgically occlude the aneurysm or endovascular occlusion via metal coils. While endovascular coils are safer, there are distinct limitations to this treatment path, including a lack of stable blood clot formation and a risk of the coil intruding into the arteries. Endovascular coils that are integrated with shape memory polymers (SMPs) have the potential to improve occlusion and reduce coil risks; however, there are some limitations on mechanical performance and homogeneity of SMP physical properties. To address this issue, SMP foams were synthesized using the monomer diethanolamine (DEA) in place of triethanolamine (TEA) to provide the mechanical properties required for medical device applications. The incorporation of DEA was confirmed spectroscopically, as demonstrated by the urethane peak that is the hallmark of this chemistry and the urea peak associated with the DEA-isocyanate reaction. The utility of the DEA foam was demonstrated via mechanical testing and shape recovery analysis, in comparison to the TEA SMP formulation. DEA foams had a comparable modulus, or stiffness, and an increased toughness compared to the control. Preliminary shape recovery experiments indicate that the incorporation of DEA increases the rate of recovery compared to that of the control. This work presents the utility of DEA in SMPs to improve mechanical toughness and enable the production of safer medical devices for use in aneurysm treatment.