Morphology of Block Copolyurethanes. II. FTIR and ESCA Techniques for Studying Surface Morphology

Abstract

Block copolymers form a domain-matrix morphology due to the chemical and steric incompatibilities of the chemically different blocks or segments. The unusual range of the physical and chemical properties associated with block copolyurethanes result from this unique morphological separation. However, multiple (AB)_n block copolymers such as block copolyurethanes may or may not have as complete phase separation as the simpler AB block copolymers. Bulk morphologies of block copolyurethanes have been studied by many investigators during the last decade via electron microscopy (1,2), temperature-modulus (3,4,5) and infrared spectroscopy (6–11). More recent studies have shown the bulk and surface chemical and morphological structures of block copolyurethanes may be quite different, and are affected by both synthetic alterations of the polymeric repeat unit and by fabrication variables (12–15). Since several block copolyurethanes have shown both compatibility and mechanical properties needed for vascular implants, it is important to determine the chemical and morphological structures of these materials. A block copolyetherurethane-urea and associated model compounds and homopolymers have been studied by Fourier Transform Infrared Spectroscopy (FTIR) and Electron Spectroscopy for Chemical Analysis (ESCA) in order to determine the chemical and morphological structures of the surface of the block copolyurethane as compared to the bulk.