Synthesis, characterization and ex vivo evaluation of polydimethylsiloxane polyurea-urethanes.

A series of segmented polydimethylsiloxane (PDMS) polyurea-urethanes was synthesized based on hexane diisocyanate modified polyether-PDMS soft segments. The hard segments consisted of 4,4'-methylene diphenylene diisocyanate, which was chain extended with 1,4-butanediol. The effect of chemical composition of the polyether-PDMS soft segments on the extent of phase separation, physical properties and surface properties was studied using a variety of techniques including dynamic mechanical analysis, tensile testing, X-ray photoelectron spectroscopy (XPS) and contact angle analysis. The polymers were also evaluated for their blood-contacting properties in a canine ex vivo model. The PDMS polyurea-urethanes containing polyether-PDMS soft segments showed three distinct phases: a PDMS-rich phase, a polyol soft segment-rich phase and a hard segment-rich phase. The tensile strength and modulus of these materials were not significantly lower compared to a polymer without PDMS in the soft segment. XPS revealed the surface enrichment of the hydrophobic PDMS component at the air-solid interface. Dynamic contact angle measurements indicated that the PDMS-based polyurea-urethanes possessed a hydrophobic surface in water. The PDMS polyurea-urethanes showed lower adherent platelet and fibrinogen deposition compared to a polymer without PDMS in the soft segment. Varying the amount of PDMS in the soft segment of these polymers did not reveal significant differences in their blood-contacting properties.