Preparation And Characterization Of Poly(diol Citrate)based Biodegradable Elastomer And Its Nanocomposite

Citric acid is one of very important reactive monomersbased on the study of network-based polyestersfor biomedicine, mainly due to its non-toxicity, belonging to human metabolic triacids, and its special molecular structure. The molecular structure of citric acid has three carboxyls, which can form cross-linking among molecular chains and thusform interpenetrating network structure through carboxyl reacting with amino or alcohol. Synthesis of network-based polyester is simple and inexpensive.Also such polysesters possess controllable biodegradability and mechanical properties, which made them have great potentials in tissue engineering. Regulating and modifying the network structure of polyesterscan satisfy various medical needs.So network-based biomaterial polyesters have broad applicational prospects.In this dissertation, Pluronic F127 was introduced intothe network structure of poly(1,8-octanediol-citric acid)(POC) by melt polycondensation toobtainpoly(1,8-octanediol-citric acid)-co-Pluronic F127(POC-co-F127) bioelastomers. And then, the chitin nano-whiskers were loaded into POC-co-F127 matrix to improve the properities of POC-co-F127 elastomers. The main results are as follows:1. POC-co-F127 bioelastomers were prepared by melting polycondensation, and the ratio of Pluronic F127, 1,8-octanediol andcitric acid and crosslinking time were explored. The structure and properties of POC-co-F127 were characterized by FT-IR, DMA, DSC etc.The results showed that Pluronic F127 was successfully introduced into the network architecture of POC; the glass transition temperature(Tg) of POC-co-F127 elastomers was reduced by introducing PluronicF127;The hydrophilicity and degradable rate were also improved; since Pluronic F127 ownsa temperature-sensitivety, POC-co-F127 elastomers also present changable water-swellable ability at certain temperature;the mechanical properties of POC-co-F127 elastomers is better than POC; when the mass fraction of F127 was 20%, the mechanical properties of POC-co-20F127 is thebest;since Pluronic F127 has the feature of blood compatibility, POC-co-F127 elastomers also exhibit blood compatibility.2. CW/POC-co-20F127 nanocomposites were prepared by adding chitin nano-whisker into POC-co-20F127 elastomer. The structure and properties of CW/POC-co-20F127 nanocomposites were characterized by FT-IR, DMA, DSC, XRD etc. The prepolymer of POC-co-20F127 prepared by melt polycondensation of Pluronic F127, citric acid and 1,8-octanediolhas water-soluble properity, and it is possible to achieve uniform mixed aqueous solution of CW and POC-co-20F127 prepolymer. Then by drying and high-temperature curing, CW well dispersed CW/POC-co-20F127 nanocomposites were obtained.The breaking strength and elastic modulus ofCW/POC-co-20F127 nanocompositeswere obviously strengthened. The introdution of CW improved cytotoxicity of POC-co-20F127 elastomer.3. CW/POC-co-20F127 porous scaffolds were prepared by lyophilization technology. The results showed only when CW loading was as high as 15%, the porous structure could be formed; the porous scaffolds showed reversible recovery from compresion, and the maxium compression stress was 241 KPa; the porosity was measured as ~80% and water-absorbability was about 500%; through analyzing the structure of CW and POC-co-20F127 prepolymer in aueous solution, the model of pore-forming mechanism was hypothesized.