Hydrolytic degradation of soybean oil-based shape memory polymer

To improve the need and availability of natural renewable shape memory polymer (SMP) materials in the biomedical field, Epoxidized Soybean Oil Acrylate (AESO) was formulated with IBOA to evaluate its hydrolytic degradation capabilities via Simulated Body Fluids (SBF) absorption. AESO is known for being a natural, biobased, cheap, and readily available renewable resource. By evaluating the hydrolytic degradation capabilities of SMP AESO IBOA, factors suitable for biomedical usage in the human body such as biodegradability and mechanical properties can be assessed. Through the 30 days Absorption test, SMP AESO IBOA has displayed significant SBF absorption capabilities with highest 87.99% SBF uptake. However, both SBF and distilled water absorption curves did not yield a stable plateau and may require longer degradation periods. The water contact angle was less than 90° indicating hydrophilicity. This contradicts AESO’s and IBOA’s hydrophobic nature. Additionally, the absorption test highlighted SMP AESO IBOA to absorb the liquid mediums it is soaked in as weight gain was seen. However, SMP AESO IBOA did not show signs of biodegradation when soaked in SBF and distilled water solution. The Swelling test highlighted the polymer’s retention of its dimension as it did not fluctuate greatly. This retention of shape entails the SMP potential usage in long-term biomedical applications. Soaking SMP AESO IBOA in SBF for up to 15,30 and 60 days for tensile testing, the results achieved after 60 days of soaking was an overall decrease of its mechanical properties such as ultimate tensile strength, elongation at break and toughness. To add on, a hardness test was also done after 93 days and a decrease in hardness value was recorded. The decrease in these mechanical properties show the occurrence of molecular hydrolytic degradation. Soaking SMP AESO IBOA in SBF has thus altered its polymer structure and allow it to display hydrolytic degradation capabilities. This allows the potential for this SMP to be used inside the human body to be evaluated. The study of its toxicity via monomer leaching and biocompatibility via cell culture can be studied to study the safety and usage inside of the human body.Bachelor of Engineering (Mechanical Engineering