Study On Poly(carbonate Urethane)s With Properties Of Shape-memory And Biostability

With the development of medical technology, and the appearance of new medical materials, the requirement of biostable materials is growing. The poly(carbonate urethane)s (PCU) are considered to be potential candidates for the next generation of implant materials with biostability and security for human. In this thesis, serials of crosslinked PCU with different ratio were synthesized, and mechanical properties, shape-memory effects and degradation behavior in PBS solution were studied.PCU was synthesized by solution two-step polymerization. Polyhexamethylene carbonate diols (PHMCD) were used as soft segments, isophorone diisocyanate (IPDI) and trihydroxylmethylene propane (TMP) as hard segments. The structure of polymer synthesized was analyzed by ATR Fourier-transform (ATR-FTIR) spectroscopy, which indicated that PCU had the structure of IPDI and PHMCD, respectively, and the amido formyl ester in polyurethanes. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) were used to characterize the thermal properties and the microphase separated structure, which affirmed that the glass transition temperatures (T_g) of PCU networks increased significantly with the increase of the molar ratio of NCO/OH and OH₁/OH₂ in the networks, and decreased with the increase of the molecular of soft segment. Besides that, the melting temperature (T_m) of PCU networks decreased with the increase of the molar ratio of NCO/OH. The initial zero gravity temperature and the temperature of maximum mass-loss rate decreased with the increase of the molar ratio of NCO/OH and OH1/OH2 in the networks.From the analysis of mechanical properties, break elongation of PCU decreased with the increase of the molar ratio of NCO/OH, while tensile stress increased significantly. From the investigation of shape-memory effect of PCU, all of R_f was close to 100 %, which showed PCU had good shape-memory effect. And the analysis of volumetric swelling degree and gel content of PCU showed that crosslinked degrees and gel content rose with hard segment content, but volumetric swelling degree decreased accordingly.Additionally, biodegradation behaviors of PCU were investigated in vitro by water absorption, weight loss and mechanical properties during the degradation of PCU film, which showed that PCU had better biostability, and their weight losses were not exceeded 0.6 % after 9 weeks in vitro. The mechanical properties of PCU2-151510 didn't change clearly, while PCU2-181510 changed largely during the degradation time. However, break elongation of PCU2-181510 was even near to 550 % and tensile stress exceeded 40 MPa after 8 weeks in vitro, which displayed better mechanical properties and biostability, while break elongation was 604 % and tensile stress was 56.6 MPa. At last, ATR-FTIR was also used to investigate chemical structures of degraded PCU films. The result showed that the frequency and intensity of absorbing has not changed obviously, which indicated that PCU had good biostability.