Structure Dependent Chemical and Biological Interactions of Poly(urethane urea)s

Doctoral thesis, 2002

Poly(urethane urea)s, PUURs, are widely used in both industrial and biological applications because of excellent physical and mechanical properties and good biocompatibility in a variety of applications. Both the processing and the tailoring of specific properties of PUUR demand great knowledge of structure-property relationships. In the present work, the effect of structural changes in the soft and the hard segments that build up the polymer backbone have been investigated with respect to hydrogen bonding and phase separation. The soft segment length and chemical structure were varied. In the hard segment chain extenders of different lengths were used and lateral substituents were introduced. In addition, methods to prevent and disrupt hydrogen bond formation were investigated. Initial in vivo and in vitro studies of one of the PUURs, PUUR-1,3-DAP, were performed to study biocompatibility. The length of the soft segment structure affected the phase separation. The longer the soft segment the more phase separated polymer. Small changes in the chain extender structure affected the hard segment to form ordered arrays induced by hydrogen bonding. The molecular factors that influence this array formation are the internal mobility and the steric interactions of the hard segment. The hydrogen bonding between the polymer chains can also be prevented by addition of solubilizing salts. The in vivo implantation studies of PUUR-1,3-DAP fibres showed good compatibility with host tissue. Further, in vitro studies of PUUR-1,3-DAP indicated cell-material responses as good as that for polystyrene and titanium. The results presented in this thesis demonstrate the importance to understand structure dependent interactions of PUURs for the development of novel PUUR materials with tailored chemical and physical properties. The understanding may also be essential for the interpretation of the biological response to these materials.