| Biodegradable polymers bear the brunt of modern and new material development and research since they are discovered and used in the late 20 th century. Thanks to the their flexibility and variety of molecular structure, accessible monomers, easy adjustment and optimization of synthesis process, biodegradable polymers are widely used in a series of industry and sectors such as biomaterials, artificial organs, prosthesis, tissue engineering, medical scaffold. Polyurethane as one of the polymer family, bears additional advantages of light-weight, quick manufacture, rich variety and has been utilized in auto industry, furniture and textile realm. With the modern technology evolving and larger demand of diverse-functioning materials, biodegradable polyurethane attracts the attention of researchers for developing new biodegradable materials since it has inherent degradable ester bonds in their structure. This paper discusses and focuses on the following issues of biodegradable polyurethane. First, the remaining and varing effects of biodegradable poly-glycol such as polylactic acid(PLA), polycaprolactone(PCL), Polypropylenecarbonate(PPC), polyethylene glycol adipate(PBA), Polytetrahydrofuran diol(PTMG) as the main sources of polyurethane synthesis on their final polyurethane products; Secondly, the effect of chain extender 2,2-Bishydroxymethylbutyric Acid(DMPA) and small molecular glycol 1,4 butanediol on several degradable performances and their modulating effect; Thirdly, the biodegradability analysis the influence factor study of polyurethane’s degree of cross linkage and molecular weight; Fourthly, the influences of choices of polyglycol on biocompatibility and enzymolysis of polyurethanes. According to these tests and study above, this paper gives some advice and enlightenment of preparing and synthesizing various sorts of polyurethanes with diverse degrading patterns and speeds. Finally this paper gives following conclusions:1. Hydrolysis characteristics of different kinds of polyglycol-polyurethanes in PBS buffering solution substantially depend on density of ester bonds on the macromolecules and surrounding molecular structures. The denser of the ester bonds and looser of their surrounding molecular structure, the easier hydrolysis ability polyurethane possess. For instances, PBA-PU and PPC-PU have higher hydrolysis degree than PTMG-PU because they have comparatively more ester bonds less hydrogen bonds in their macromolecule while PTMG-PU is much tighter in macromolecule structure and has larger numbers of hydrogen bonds.2. Under the same choice of poly-glycol, polyurethane’s micro phase separation degree, cross linkage as well as crystallinity degree can be modified with using different ratios of chain extender(DMPA) and hard-segment additive(BDO). Experiments show that higher ratio usage of chain extender in synthesis can enhance the polyurethane’s molecular cross linkage degree and slights foster its hydrolysis while its biodegradability ability is reduced. More usage of BDO can definitely enlarge polyurethane’s micro phase separation and thus create larger proportions of crystallinity causing decreasing biodegradability while hydrolysis almost unaltered.3. Experiments also find that the choice of poly-glycol in the synthesis of polyurethanes ultimately decides the biocompatibility and enzymolysis among which PCL-PU and PLLA-PU show satisfactory biocompatibility and greater enzymolysis than their counterparts. Besides, Bone cell compatibility test(almmarblue) indicates that PCL-PU and PLLA-PU also boosts the growth of cell’s reproduction by supporting a matrix surface holding the biomass.4. By the method of molecular modification, polyurethane’s general mechanic proper can be flexible by adding silicone oil grafting to the macro-molecule which can improve heat resistance and modulus to a certain extent. In addition, PEG can also be used to copolymerize the polyurethane gaining a higher degree of both hydrolysis and biodegradability. |
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