title: Prevention of oxidative degradation of polyurethane by covalent attachment of di-tert-butylphenol residues.
abstract: Polyurethane (PU) components of cardiovascular devices are subjected to oxidation-initiated surface degradation, which leads to cracking and ultimately device failure. In the present study, we investigated a novel bromoalkylation chemical strategy to covalently attach the antioxidant, di-tert-butylphenol (DBP), and/or cholesterol (Chol) to the PU urethane nitrogen groups to hypothetically prevent oxidative degradation. These experiments compared PU, PU-DBP, PU-Chol, and PU-Chol-DBP. A series of comparative oxidative degradation studies involved exposing PU samples (modified and unmodified) to H2O2-CoCl2 for 15 days at 37 degrees C, to cause accelerated oxidative degradation. The extent and effects of degradation were assessed by attenuated total reflectance Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM), surface contact angle measurements, and mechanical testing. Both the Chol and DBP modification conferred significant resistance to oxidation related changes compared to unmodified PU per FTIR and SEM results. SEM demonstrated cavitation only in unmodified PU. However, contact angle analysis showed significant oxidation-induced changes only in the Chol-modified PU formulations. Most importantly, uniaxial stress-strain testing revealed that only PU-DBP demonstrated bulk elastomeric properties that were minimally affected by oxidation; PU, PU-Chol, PU-Chol-DBP showed marked deterioration of their stress-strain properties following oxidation. In conclusion, these results demonstrate that derivatizing PU with DBP confers significant resistance to oxidative degradation compared with unmodified PU.
authors.affiliation: Division of Cardiology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104-4318, USA.
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Stachelek
authors.forename: Ivan
authors.initials: I
authors.lastname: Alferiev
authors.forename: Hoon
authors.initials: H
authors.lastname: Choi
authors.forename: Chun Wai
authors.initials: CW
authors.lastname: Chan
authors.forename: Brett
authors.initials: B
authors.lastname: Zubiate
authors.forename: Michael
authors.initials: M
authors.lastname: Sacks
authors.forename: Russell
authors.initials: R
authors.lastname: Composto
authors.forename: I-Wei
authors.initials: IW
authors.lastname: Chen
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Levy
mesh_terms: D002073:Butanes / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction; D019800:Phenol / Q000737:chemistry*; D011140:Polyurethanes / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D002073:Butanes; D011140:Polyurethanes; D019800:Phenol