Shape-Memory Properties of Radiopaque Micro-Composites from Amorphous Polyether Urethanes Designed for Medical Applicati
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Shape-Memory Properties of Radiopaque Micro-Composites from Amorphous Polyether Urethanes Designed for Medical Application J. Cui, K. Kratz and A. Lendlein Center for Biomaterial Development, Institute of Polymer Research, GKSS Research Center Geesthacht GmbH and Berlin-Brandenburg-Center for Regenerative Therapies (BCRT), Kantstrasse 55, 14513 Teltow, Germany ABSTRACT Biocompatible shape-memory polymers are of high significance for application in medical devices or instruments for minimally invasive surgery. To follow the medical device placement or changes in shape of the device in vivo by imaging methods like X-ray techniques, radiopacity of the polymer is required. In this work, we explored the shape-memory properties of radiopaque polymer composites prepared by incorporation of barium sulphate micro-particles in a biomedical grade polyether urethane (PEU) by co-extrusion technique. The filler content was varied from 5 wt% to 40 wt%, which was confirmed by thermal gravimetric analysis (TGA) measurements, while the particle distribution was visualized by scanning electron microscopy (SEM). The thermal and mechanical properties of the composites were investigated by means of dynamic mechanical analysis at varied temperature (DMTA) and tensile tests. The shapememory properties of PEU composites were quantified in cyclic, thermomechanical experiments. A significant increase in Young’s modulus and a decrease in elongation at break were observed for PEU composites with increasing content of BaSO4, while the DMTA results were not affected by incorporation of the fillers. All samples exhibited excellent shape-memory properties with shape fixity rates (Rf) above 98% and values for shape recovery rate (Rr) in the range of 81% to 93%. The maximum stress (σmax) obtained under constant strain recovery conditions increased from 0.6 MPa to 1.4 MPa with raising amount of BaSO4, while the corresponding temperature (Tσ,max) as well as the switching temperature (Tsw) determined under stress-free conditions remained constant for all polymer composites. INTRODUCTION Shape-memory polymers (SMP) have attracted tremendous interest due to their substantial innovation potential in different application areas, e.g. as intelligent implant materials in medicine [1-3] or in smart textiles [4]. An important class of thermoplastic shape-memory polymers are polyurethanes, which have been applied in artificial heart, heart valves, pacemaker connectors, catheters, vascular stents, suture materials and matrices for controlled drug release [5]. For numerous medical applications inside the human body it is necessary to control the device placement by imaging techniques like X-ray. The most common technique to realize Xray contrast properties for polymers is the incorporation of radiopaque fillers like barium sulphate (BaSO4). We explored the fabrication of radiopaque polymer composites from a biocompatible polyether urethane (PEU) with shape-memory capability and BaSO4 micro-particles with various filler contents. The thermal and mecha
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