Materials and Manufacturing

Medical device developers have had a very limited choice of implant materials for highly demanding applications such as insulation for pacing leads, long term in-dwelling catheters, synthetic polymer heart valves and coronary vascular grafts. All of these applications require polymers that have excellent biostability, good mechanical strength and high resistance to fatigue, abrasion and tear.

Traditionally, silicone rubber was the material of first choice, because of its excellent biostability, despite shortcomings in the other material properties. Polyurethane, which is a generic name for a very large family of synthetic polymers, has emerged as the principal alternative to silicone rubber because of superior mechanical properties. These properties are attributable to the fact that polyurethanes are polymers that comprise a combination of both soft and hard segments. Unfortunately, early success was followed by disappointment, as the flexible versions of polyurethane did not have adequate biostability. The principal problem has been the degradation of the soft segment of the polyurethane.

Many families of polyurethanes, named Elasteon, were developed and are now licensed exclusively to Elastomedic. Elasteon, is an improvement on conventional polyurethane in that it has a reduced number of the susceptible chemical groups

manufacture and method of making and implanting material made of a polyolefin star or linear copolymer are disclosed in which the polyolefin copolymer is biostable and crack-resistant when implanted in vivo. The polyolefin copolymer is the reaction product of a rubbery component which when homopolymerized produces a polymer having a low level of hardness, and a hardening component which when homopolymerized produces a polymer having a high level of hardness. The polyolefin copolymer is elastomeric, has a hardness intermediate the low and high levels of hardness, and has a backbone in which the majority of polymer linkages along the copolymer chain are alternating quaternary and secondary carbon atoms.