Carbon Nanotubes - Preparation Of Polyurethane-based Composite Materials And Biocompatibility Study

Hemocompatibility has been an important issue of biomedical material research for decades. Once blood contacts with heterogenous materials, many unexpected effects happen, such as blood coagulation, hemolysis and white blood cell denature, which is the result of non-specific adsorption of serum protein molecules, followed by adherence and activation of blood cells. The most serious outcome among all the above are intravascular blood coagulation and thrombosis formation, which would be fatal to the patients. So, being with good anti-coagulant property is crucial necessary for a promising biomedical material.Among all the synthetic polymers, polyurethane (PU) has been an important candidate material applied in artificial organs and medical appliance industry for its relatively acceptable biocompatibility and mechanical properties. But till now, not any of synthetic polymers have properties close to human endothelium. As a result, high dosage or long term anti-coagulation treatments have to take while any artificial material is applied in blood-contact environment, which may cause severe complications to the patients. Numerous of methods have been tried to improve the blood compatibility of synthetic polymers, particularly of PU. Although progresses have been made, there is still none modified PU which can perfectly meet the of the blood compatibility requirement applied in blood system, for example, artificial blood vessels with small diameter (diameter<6mm) has been an occlusion. Still to say, most modifications of PU for hemocompatibility improvement cause adverse effects to its mechanical properties.With the rapid development of nanoscience and technology, inorganic-organic nanocomposite has become a brand new way for functional material development. Carbon materials have been found with excellent hemocompatibility. For example, low temperature isotropic carbon (LTIC) has been used in surface coating for artificial heart valve. Carbon nanotubes (CNTs) is a new member of carbon family. Its wonderful mechanical properties allow it to be perfect enhancement element for composites preparation, as well as to improve the hemocompatibility of polymeric matrice greatly for its pure carbon composition.Based on the sol-gel precipitation in co-organic solvents method established by our laboratory, following research has been conducted and completed in this work:First, the key conditions and parameters in the preparation have been optimized. The original multi walled carbon nanotubes (MWNTs) was purified by concentrated HCL. Ultrasonic assisted mixed strong acids were applied to introduce hydrophilic oxygen-containing functional groups to the sidewalls of MWNTs, which plays important role in the dispersion of MWNTs in water-like organic solvents and formation of homogeneous composite of MWNTs and PU.Second, the physical and chemical properties of MWNT-PU were characterized and analyzed, including measuring the tensile strength and elongation by universal pulling machine, measuring the viscosity of composite solution, analyzing the thermal behaviors and microphase separated structures of MWNTs-PU by DSC, analyzing surface chemical elements and relative contents using XPS. All the results revealed that the introduction of MWNTs to PU matrix could change...