H The-htbn-b-peg Polyurethane Block Copolymers, Micro Phase Separation Behavior And Biomedical Properties

With the development of science and technology as well as the improvement of people's living standards, medical polyurethane industries are undergoing rapid changes. So far, it is still not satisfied although great progress has been made in the biocompatibility and mechanical properties of the medical polyurethanes. Therefore, improving the biocompatibility and mechanical properties of the biomedical PUs becomes a significant issue, and has attracted extensive attention in the past decades. Since microphase separation, surface morphology (for example surface roughness), chemical composition and hydrophilicity influence protein adsorption, biocompatibility, cellular growth and activation; particularly, the unique biomedical properties of PU copolymers are directly related to their special two-phase microstructure. Therefore, some underlying factors influencing the biocompatibility and mechanical properties are explored in depth based on the surface hydrophilic modification of polyurethane copolymers and special two-phase microstructure in this work.Firstly, novel h-HTBN-b-PEG biomedical polyurethanes are synthesized by coupling hydrolytically modified hydroxyl-terminated poly(butadiene-co-acrylonitrile) (h-HTBN) with poly(ethylene glycol) (PEG) together as soft segments, with the help of 1,1-methylene bis-(4-isocyanatocyclohexane) (H12MDI) as a bridging reagent (the hard segment). The PUs with different performances can be prepared by controlling the ratio of the two soft segments (h-HTBN and PEG), the hydrolysis time of HTBN and molecular weight of PEG. The structure of PU copolymers is characterized by Fourier transformation infrared spectrometry (FTIR).Secondly, we have examined micro-phase behavior of the series h-HTBN-b-PEG PU because their thermal-mechanical properties and biocompatibility were affceted by the unique phase structure. The phase behavior of the as-prepared polyether polyurethane (PU) elastomers was investigated by dynamic mechanical analysis (DMA), polarized optical microscope (POM), and atomic force microscopy (AFM). The microphase separation behavior is confirmed to occur between soft and hard segments as well as soft and soft segments as the h-HTBN is incorporated into the PU system, depending on soft-soft and/or soft-hard microdomain composition, molecular weight (MW) of PEG, and hydrolysis time of HTBN. The driving force for this phase separation is mainly due to the formation of inter- and intramolecular hydrogen bonding interaction. The PU-70, PU-50 samples with non-reciprocal composition seem to exhibit larger microphase separation than any other PU ones. The thermal stability and mechanical properties of the copolymers were assessed by gravimetry, scanning electron microscope (SEM), thermal gravity analysis (TGA), and tensile test, respectively. The experimental results indicated that the incorporation of h-HTBN soft segment into PEG as well as low MWof PEG leads to increased thermal and degradable stability based on the intermolecular hydrogen bond interaction. The PU-70 and PU-50 copolymers exhibit better mechanical properties such as high flexibility and high ductility because of their larger microphase separation architecture with the hard domains acting as reinforcing fillers and/or physical crosslinking agents dispersed in the soft segment matrix.Finally, we have studied the hydrophilicity, hemocompatibility, cytotoxicity, and hydrolysis degradation of novel polyurethane (PU) scaffolds for tissue engineering, especially the hydrolysis effect of a soft-segmented component h-HTBN on these properties. These PU copolymers have proved to be highly blood compatible asdemonstrated by hemolysis platelet activation and hydrolysis degradation stability. The hydrolysis modification of HTBN and optimal combination of the two soft segments can remarkably reduce or inhibit platelet activation, adhesion, and aggregation, improving anti-clotting properties. MTT assays have disclosed that the newly developed PU copolymers show component ratio and degree of hydrolysis dependence on the cytotoxicity and proliferation of HEK cells. These are believed to be correlated with the improved surface hydrophilicity as revealed by the surface water absorption and contact angle measurements. The gravimetry and scanning electron microscope (SEM) results show that the PUs exhibit degradation stability.It is expected that low toxic PU biomaterials can be prepared by the hydrolysis modification of HTBN and mediating the constitution of HTBN or h-HTBN and PEG.In a word, we have studied in-depth on the microphase separation behavior, thermal-mechanical properties, hydrophilicity, hemocopatibility and degradation behavior of the series of the newly developed h-HTBN-b-PEG PU scaffolds. The results are excited that the novel PUs are thought to be an important new class of biocompatible materials and can be employed as potential candidates for blood contacting applications.