Synthesis and characterization of biocompatible polyurethanes functionalized by chitin and curcumin

Abstract

Polyurethanes belong to synthetic class of polymers and their tailor made properties make them a suitable candidate for biomedical applications. Their properties can be tuned by the careful selection of monomers e.g., isocyanates, polyols and chain extenders. In this present project, set of thermoset and thermoplastic polyurethane elastomers have been synthesized and characterized by using different analytical tools. In first part, thermoset polyurethane elastomers were synthesized by step growth polymerization through reaction of chitin, toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) and hydroxy terminated polybutadiene (HTPB) and extended with 1,4-butanediol and curcumin. Twenty different samples of thermoset polyurethane elastomers have been synthesized by varying the diisocyanate and molecular weight of HTPB. In next step, chemical structure of synthesized polyurethanes was confirmed by solid state nuclear magnetic resonance spectroscopy (SS1HNMR) and Fourier transform infrared spectroscopy (FTIR) techniques. FTIR spectroscopy was employed for studying structural features of polyurethane blends which confirmed 1,4 butanediol (1,4-BDO) and curcumin incorporation within polyurethane matrix. Thermal stability of PU blends was evaluated by thermogravimetric analysis (TGA) which revealed that upto 240oC, all samples of polyurethane were stable and their degradation occurred at 300oC. X-ray diffractometry analysis was used for determination of crystallinity and results indicated that polyurethane samples were semi crystalline and no significant difference in crystallinity index has been noted by varying the nature of diisocyanate and molecular weight of HTPB. SEM analysis was conducted to study the surface features of polyurethanes extended with chain extenders and results revealed their incorporation into polyurethane matrix and surface was transformed from homogenous to heterogeneous. Hydrophobicity/hydrophilicity of synthesized polyurethanes was tested through water absorption capacity (%) and contact angle measurement which showed that HTPB based polyurethanes were hydrophobic. Antibacterial activity was measured using agar diffusion method which revealed outstanding antibacterial property against selected bacterial strains. Therefore, antioxidant, antibacterial and hemolytic activities of purposed polyurethane elastomers were improved by curcumin incorporation. Reliable results were obtained through present study inferred that both 1,4-BDO and curcumin successfully incorporated in polymeric chains with significant effect on morphological and thermal aspects. A significant difference in biological response has been noted by increasing the molecular weight of HTPB. In the second part, ten samples of thermoplastic polyurethanes were prepared by compounding extrusion process and to confirm the purposed structure of polyurethanes, FTIR spectroscopic investigation was carried out. Crystallinity pattern of thermoplastic polyurethanes was confirmed by the XRD and immiscibility of blended thermoplastic polyurethanes was examined by SEM which suggested the incorporation of nanoclay-chitosan-curcumin, individually and together in a blend and starch-chitosan individually and in a blend into the PUs matrix. Biological behaviour was evaluated by using some biological test (e.g. antibacterial, antioxidant and hemolytic) to observe the biocompatibility of thermoplastic polyurethanes. The biological properties were found to be improved by the addition of curcumin along with chitosan in comparison to starch along with chitosan. Overall, it was concluded that PUs synthesized in second part can be used as non-absorbable sutures in biomedical field.