Polyurethane: A Versatile Scaffold for Biomedical Applications

Polyurethanes (PUs) are one of the most versatile and explored polymeric materials in which the urethane groups are the major repeating unit and can be synthesized by reacting di or polyisocyanates (hard segments) with di or polyols (soft segments) via catalyzed polymerization process [1]. A broad range of PU with variety of physical and mechanical properties can be tuned just by changing the ratio of soft and hard segments [2]. Thus, it consists of two phase structure in which the hard segments are embedded into the soft segments. Using different ratios of hard/soft segments, it can be fabricated according to their need of applications in rubber, fibers, films, paints, coatings, elastomers, foams, gels etc. [3] These many forms of PUs available to date are simple improvements of the invention of Dr. Otto Bayer and his coworkers in the 1930s [4]. The continuous improvements in the polyurethane made them a suitable and promising material for the incorporation in widespread applications. For the decades, it has been used in the field of biomedical due to their well-known properties such as good durability, high tensile strength, fatigue resistance, excellent biodegradability and biocompatibility [5]. Among the polymers like, silicone, polyvinyl chloride (PVC), polyethylene and poly tetra fluoro ethylene (PTFE), PUs are widely used in medical application due to their superior bio and hemo compatibility. On account of this very characteristic property, they have extensively been used in catheters, heart valves, vascular grafts, prostheses and blood coagulating devices [6].