Synthesis of bile acid, poly (ε-Caprolactone) and ʟ-Lysine diisocyanate ethyl ester based polyurethanes and investigation of their biodegradability properties

In today's developing world, the need for bio-based materials shows an increasing trend. The necessity of these bio-based materials has substantially increased, making them one of the broadly utilized materials over numerous applications. In this regard, polyurethanes and polyactones are emerging as suitable candidates and are currently finding applications in a variety of fields, from the packaging and food industries to medical and pharmaceutical applications. On the other hand, bile acids are natural compounds that play an important biological role in the body. Therefore, they are preferred candidates as building blocks of biocompatible and degradable polymers. In addition, the presence of ʟ-lysine diisocyanate ethyl ester, which is a biocompatible and non-toxic diisocyanate in the structure of the material to be obtained, may give a different perspective depending on the application to be used. For all these aforementioned reasons, combining bile acid, poly (ε-caprolactone) and ʟ-lysine diisocyanate ethyl ester under the same skeleton will result in the emergence of a fully biobased polyurethane. In this thesis, a series of environmentally friendly polyurethane (PU) films were successfully synthesized. For this purpose, ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) in the presence of cholic acid (CA) initiator, step-growth polymerization (SGP) between achieved CA based poly (ε-caprolactone) (CA-PCL) and ʟ-Lysine diisocyanate ethyl ester (ʟ-LDI), and solution casting method were used, respectively. The effect of using different feeding ratios of ε-CL monomer (CA:ε-CL=1:60, 1:75 and 1:90, by mole) on the properties of PUs were investigated in detail by fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopies, gel permeation chromatography (GPC), water contact angle (WCA) measurements, thermogravimetric and differential scanning calorimetry analyses (TGA and DSC) and mechanical tests, respectively. Moreover, biodegradation tests in the absence or presence of porcine pancreatic lipase were conducted to determine the degradation behaviors of resulted PURs. It was found that a higher proportion of ε-CL repeating units in the PU backbone caused the improvement in hydrophobicity, thermal and mechanical properties, while leading to the deterioration in degradation behavior. Furthermore, biodegradation studies revealed that CA-PCL-PUs were more degradable in both hydrolytic and enzymatic media compared to PCL-PU synthesized without CA. The results of this thesis study proved to CA, PCL and ʟ-LDI based biodegradable PU films have great potential for application in particularly tissue engineering and wound dressing.