Polyisobutylene-based polyurethanes. VI. Unprecedented combination of mechanical properties and oxidative/hydrolytic stability by H-bond acceptor chain extenders

Abstract

We describe the design, synthesis, characterization, and testing of novel polyurethanes (PUs) exhibiting unprecedented combinations of outstanding mechanical properties and oxidative/hydrolytic stabilities. This achievement is due to the use of polyisobutylene (PIB) soft segments plus flexible H-bond acceptor chain extenders (HACEs): the PIB imparts superior oxidative/hydrolytic stability and the HACE produces reinforcing H-bonds, which lead to outstanding mechanicals. Oxidative/hydrolytic stability was quantitated by retention of tensile strength and elongation after exposure to nitric acid. PUs containing 60–70% PIB retain their mechanical properties, whereas Carbothane®, Bionate®, and Elast-Eon™, PUs marketed for chemical stability, degrade severely under the same conditions. Various HACEs were identified (e.g., hexaethylene glycol, tripropylene glycol, tributylene glycol, 3,3′-diamino-N-methyl-dipropylamine, etc.) and their effect on mechanical properties was investigated. A PIB- and HACE-containing PU exhibited 29.2 MPa tensile strength, 620% elongation, and 80 Shore A hardness. Properties were analyzed in terms of stress–strain profiles, differential scanning calorimetry traces, dynamic mechanical thermal analysis plots, and oxidative/hydrolytic stability. The properties of various PIB-based rubbers, that is, thermoplastic PUs, SIBSTAR®, and thermoset butyl rubber are compared. The novel PUs are promising candidates for biomaterials and industrial applications where a combination of mechanical properties and oxidative/hydrolytic stability is of the essence. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2361–2371, 2010