Structure–Property Relationships in Biomedical Thermoplastic Polyurethane Nanocomposites

Abstract

Polyurethanes are excellent potential materials for the construction of implantable medical components due to their exceptional mechanical properties and biocompatibility. Currently, soft silicone materials are employed as insulation for implantable cochlear electrode arrays. Siloxane-based thermoplastic polyurethane (TPU) nanocomposites containing synthetic layered silicates are being investigated as new insulation materials with superior tensile and tear strength and reduced surface tack, potentially allowing for thinner insulation and more intricate electrode designs. In this work, ElastEon E5-325 (Aortech Pty Ltd.) TPU nanocomposites reinforced with 2 and 4 wt % low aspect ratio organo-hectorite and high aspect ratio organo-fluoromica (Lucentite SWN, Somasif ME100, both modified with octadecyltrimethylammonium (ODTMA)) were prepared by a solvent casting technique. The mechanical properties of the resulting nanocomposites were measured by tensile, tear, stress relaxation, and creep testing and morphologically were characterized by DSC, DMTA, XRD, TEM, and strained in situ synchrotron SAXS. We found that the hydrophobic low aspect ratio organohectorite acts as a very potent interfacial compatibilizer. At 2 wt % loading, the resulting nanocomposite displays vastly superior mechanical properties to both soft silicone and ElastEon. In addition to providing 30 nm × 1 nm synthetic nanosilicate reinforcing elements which are readily capable of orientation and reinforcement, these nanosilicates also serve to provide more cohesive hard microdomains and thus creep resistance and dimensional stability. Interestingly, at a higher (4 wt %) loading of organohectorite, gross morphological changes in the TPU microdomain texture are observed, adversely effecting the mechanical properties of the TPU.

Controlled assembly of superparamagnetic iron oxide nanoparticles on electrospun PU nanofibrous membrane: A novel heat-generating substrate for magnetic hyperthermia application

“…Polyurethanes are excellent potential materials for the construction of implantable medical components due to their exceptional mechanical properties and biocompatibility [24][25][26]. Hence, the nanocomposite PU in electrospun form is a promising candidate for polymeric cover of nonvascular stents, which is employed in order to inhibit the overgrowth of malignant tissues that could cause blockage of passageway such as in the case of esophageal cancer [27].…”

Effect of different polyethers on surface and thermal properties of poly(urethane-siloxane) copolymers modified with side-chain siloxane

“…The modification of polyurethanes by siloxane is mostly achieved by introduction of usually linear polydimethylsiloxane into PU backbone as a part of soft segments [4,[6][7][8]. However, the investigations on polyurethanes with other polysiloxane structure have been recently developed [9][10][11][12].…”

Fluoromica nanoparticle cytotoxicity in macrophages decreases with size and extent of uptake

“…1 The addition of layered silicate nanoparticles to different polyurethanes can form nanocomposites with significantly increased tensile strength and breaking strain. 2,3 These nanocomposites have the potential to increase the life span of biomedical devices that suffer from wear in vivo. However, all polyurethanes exhibit some degree of biodegradation, which would lead to the release of nanoparticles at the site of implantation.…”