Study On Synthesis, Structure And Property Of Degradable Polyurethane Copolymers

Degradable polyurethane could improve the mechanical property based on holding degradability of prepolymer to a certain extent, such as aliphatic polyester, poly(ether-ester), and poly(ether-ester amide), etc. Due to its great tunable property, degradable polyurethane could be widely used in many fields, including tissue engineering, drug control and release system, medical plant materials, and so on.To meet various requirements for different application in biomedical materials field, in this dissertation, three kinds of degradable polyurethanes were successfully synthesized by designing their chemical compositions and synthesis techniques. These as-prepared copolymers had various degradability and mechanical property, for example, PE-U copolymers with great mechanical property and low degradation rate, PEE-U and PCEC-U copolymers with lower mechanical property and higher degradation rate, PEEA-U copolymers with great mechanical property and higher degradation rate. And the relationship between their structures and properties was studied in detail.The main work and conclusions were listed as following:1. A series of degradable aliphatic poly(ester urethane) copolymers (PE-U) based onε-caprolactone (ε-CL), adipic acid (AA), 1,6-hexanediol (HD), and toluene diisocyanate (TDI) were synthesized by melt polycondensation method.2. A series of degradable aliphatic poly(ether-ester urethane) copolymers (PEE-U) based onε-caprolactone (ε-CL), adipic acid (AA), 1,6-hexanediol (HD), poly(ethylene glycol) (PEG), and toluene diisocyanate (TDI) were synthesized by melt polycondensation method.3. A series of degradable poly(ether-ester urethane) copolymers (PCEC-U) based onε-caprolactone (ε-CL), poly(ethylene glycol) (PEG), isophorone diisocyanate (IPDI), and 1,4-butanediol (BD) were synthesized by quasi-prepolymer method.4. A series of degradable poly(ether-ester amide urethane) (PEEA-U) copolymers were prepared by melt polymerization fromε-caprolactone(ε-CL), 6-aminocaproic acid (AC), poly(ethylene glycol) (PEG), and toluene diisocyanate (TDI).These copolymers obtained were characterized by ~1H-NMR, FTIR, GPC, DSC, WAXD, and TGA/DTG analysis. The results indicated that the synthesis was successful and controllable, and the chemical composition had great effect on their crystallization behavior, thermal degradation behavior, and the solubility in various solvents.The water absorption in distilled water at 37℃, hydrolytic degradation behavior in PBS solution (pH=4.0, 6.8, 7.4, 9.1) at 37℃, degradation behavior in garden soil, and alkaline degradation behavior in 0.01mol/L or 0.1mol/L NaOH solution at 37℃of these polyurethane copolymers were also investigated, respectively. And the experimental results showed that the copolymer chemical composition in soft segments (such as the content of PEG or PCL, the molecular weight of PEG or PCL block, etc.), the content of hard segments, the reaction time, the macromolecular weight, and the pH value of the degradation medium, had great effect on the water absorption and the hydrolytic degradation behavior of the above polyurethane copolymers.Due to the difference in the chemical composition and structure of these polyurethane copolymers, their mechanical strength and degradation rate were distinctly different. In this dissertation, the applications of these as-prepared copolymers in tissue engineering or drug control and release fields were simply explored according to their various characteristics, respectively. (1) The mean diameters of approximately 40μm BSA loaded PCEC-U microspheres were prepared by W/O/W emulsion solvent evaporation method.(2) The degradable PEEA-U fibers were prepared by the melt spinning method. For the same kind of degradable fibers, with the increase in drawing ratio, the mechanical strength increased, but the elongation at break decreased accordingly.(3) The degradable n-HA/PEEA-U-E composite films were prepared by solvent casting method through simulating composition of natural bone tissue. The structure and property of n-HA/PEEA-U-E composites were investigated through TEM, FTIR, XRD, SEM and EDX analysis. And the effect of composites on the growth of osteoblast cultured in virtro was primarily studied so as to evaluate its osteoblast-compatibility and potential to be used as biomaterials. The results showed that PEEA-U-E copolymers and n-HA/PEEA-U-E composites were not cytotoxic to osteoblast and were a kind of promising materials in clinical use.In conclusion, the study on synthesis, structure and property of three kinds of degradable polyurethane copolymers in this dissertation, provided some experimental basis on seeking new economical components, and environment kindly synthesis techniques, and improving general property of degradable polyurethane copolymers. And these would have basic effect to a certain extent on exploiting application potential of degradable polyurethane copolymers in biomedical fields.