Polyisobutylene-Based Polyurethanes. II. Polyureas Containing Mixed PIB/PTMO Soft Segments SURESH K. JEWRAJKA, 1 JUNGMEE KANG, 1 GABOR ERDODI, 1 JOSEPH P. KENNEDY, 1 EMEL YILGOR, 2 ISKENDER YILGOR 2 1 Institute of Polymer Science, The University of Akron, Akron, Ohio 44325-3909 2 Department of Chemistry, Koc University, Sariyer 34450, Istanbul, Turkey Received 14 January 2009; accepted 23 February 2009 DOI: 10.1002/pola.23361 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The design, synthesis, characterization, and structure–property behavior of polyureas containing novel soft segments of mixed polyisobutylene (PIB)/poly(tetra- methylene oxide) (PTMO) chains and conventional hard segments is presented. Modest amounts (12%) of PTMO in the soft PIB phase significantly increase both the tensile strength and elongation of the polyureas. These polyureas exhibit not only oxidative/ hydrolytic stabilities far superior to Bionate V R and Elast-Eon V R considered the most oxi- datively stable polyurethanes on the market but also display mechanical properties (29 MPa tensile strength and 200% elongation) approaching those of conventional ther- moplastic polyurethanes. The surfaces of these polyureas are covered/protected by PIB segments, which will lead to excellent biocompatibility. Our results demonstrate that the PTMO segments facilitate stress transfer from the continuous mixed soft phase to the dispersed hard phase, which strengthens and flexibilizes PIB-based polyureas and thus significantly improves elastomeric properties without compromising oxidative and hydrolytic stability. V V C 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2787– 2797, 2009 Keywords: biomaterials; elastomers; hydrolytic/oxidative stability; polyisobutylene; polyurea; polyurethanes INTRODUCTION Commercially available thermoplastic polyure- thanes, polyureas, and polyurethaneureas con- taining polyether or polycarbonate soft segments exhibit a combination of excellent mechanical properties and biocompatibility but rather poor hydrolytic/oxidative/biological stability. 1–4 In con- trast, polydimethylsiloxane-based polyurethanes and polyureas exhibit oxidative- and bio-stabil- ities superior to polyether and polycarbonate- based polyurethanes, 3,5 but only modest mechani- cal properties, and very poor acid/base (hydro- lytic) stability. 6,7 Our first paper in this series concerned the syn- thesis and characterization of polyisobutylene (PIB)-based elastomeric polyureas with unprece- dented hydrolytic and oxidative stability, and promising mechanical properties. 8 We continued research in this area to gain insight into the syn- thesis and structure–property relationship of these rubbers modified with varying amounts of poly (tetramethylene oxide) (PTMO), with the objective of creating new PIB-based polyurethanes exhibit- ing mechanical properties comparable to those of Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 47, 2787–2797 (2009) V V C 2009 Wiley Periodicals, Inc. Correspondence to: J. P. Kennedy (E-mail: josep19@ uakron.edu) 2787