title: Comparison of two antioxidants for poly(etherurethane urea) in an accelerated in vitro biodegradation system.
abstract: Vitamin E (+/-alpha-tocopherol) was recently investigated as an antioxidant for implanted poly(etherurethane urea) (PEUU) elastomers. In that work, vitamin E prevented chemical degradation of biaxially strained PEUU up to 5 weeks implantation, and prevented pitting and cracking of the PEUU surface for the duration of the 10-week cage implant study. The promising results of the in vivo studies motivated a detailed comparison of vitamin E with Santowhite, the standard antioxidant used in PEUU elastomers. To evaluate vitamin E and Santowhite as antioxidants in PEUU, an accelerated in vitro treatment system was used that mimics the in vivo degradation of PEUUs. Vitamin E was even more effective than Santowhite in preventing pitting and cracking to the biaxially strained PEUU elastomers. The inhibition of ether oxidation was greater with vitamin E than with Santowhite when compared by equivalent concentrations and molar concentrations, respectively. It is hypothesized that the increased effectiveness of vitamin E in this system, compared to Santowhite, is due to differences in antioxidant mechanism(s). Vitamin E is more efficient in preventing PEUU oxidation than Santowhite because its phenoxy radical is more stable and it can terminate more than one chain per vitamin E molecule.
authors.affiliation: Department of Macromolecular Science, Case Western Reserve University, Cleveland, Ohio 44106, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Schubert
authors.forename: M J
authors.initials: MJ
authors.lastname: Wiggins
authors.forename: J M
authors.initials: JM
authors.lastname: Anderson
authors.forename: A
authors.initials: A
authors.lastname: Hiltner
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry*; D002084:Butylated Hydroxytoluene / Q000031:analogs & derivatives* / Q000737:chemistry; D004987:Ethers / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction; D011140:Polyurethanes / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014810:Vitamin E / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D001672:Biocompatible Materials; D004987:Ethers; D011140:Polyurethanes; D014810:Vitamin E; D002084:Butylated Hydroxytoluene; C030594:Santowhite powder; C044690:polyetherurethane urea