Synthesis and characterization of bile acid, poly (epsilon-caprolactone) and (L)-lysine diisocyanate ethyl ester based polyurethanes and investigation of their biodegradability properties

Abstract

A series of environmentally friendly polyurethane (PU) films are successfully synthesized. For this purpose, ringopening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) in the presence of cholic acid (CA) initiator, step-growth polymerization between achieved CA based poly (epsilon-caprolactone) (CA-PCL) and L-Lysine diisocyanate ethyl ester (L-LDI), and solution casting method were used, respectively. The effect of using different feeding ratios of epsilon-CL monomer (CA:epsilon-CL = 1:60, 1:75 and 1:90, by mole) on the properties of PUs are investigated in detail by fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (H-1 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 are conducted to determine the degradation behaviors of resulted PURs. It has been found that a higher proportion of epsilon-CL repeating units in the PU backbone cause the improvement in hydrophobicity, thermal and mechanical properties, while leading to the deterioration in degradation behavior. Furthermore, biodegradation studies have led to conclude that CA-PCL-PUs are more degradable in both hydrolytic and enzymatic media compared to PCL-PU synthesized without CA. This study proved to CA, PCL and L-LDI based biodegradable PU films have great potential for application in particularly tissue engineering and wound dressing.