Synthesis And Properties Of Biodegradable Thermoplastic Composite Materials Based On Chitosan Oligosaccharide For Medical Applications

Chitosan oligosaccharide (CSO) is a kind of natural polymer with goodbiodegradability, biocompatibility and bioactivity. Polycaprolactone (PCL) is a kind ofsynthetic polymer with excellent biodegradability, biocompatibility and drug permeability.Biological materials based on CSO were prepared with CSO and PCL, they will be ofimportant scientific reference value and great application prospect, and they should beapplicable for biodegradable medical material, drug delivery carrier and tissue engineering.The main contents and results list below:1. Phthaloyl chitosan oligosaccharide precursor (PHCSO) was prepared through thereaction of Phthalic anhydride with the amino group of CSO in a solvent of N, N dimethylformamide (DMF). The results showed that the solubility of PHCSO had been improved inDMF, DMSO and Pyridine. XRD and DSC indicated that PHCSO changed the originalcrystal structure of CSO, and formed a new type of crystal structure. TGA indicated thatthe decomposition temperature of PHCSO was higher than that of CSO. SEM indicatedthat the ball structure of CSO had been changed and the surface morphology of PHCSObecame lamellar.2. The phthaloyl chitosan oligosaccharide-g-polycaprolactone (PHCSO-g-PCL) wassynthesized by coupling the hydroxyl group using direct method via the ring-opening graftcopolymerization of ε-caprolactone onto the backbone of PHCSO and indirect method ofacid functional group of PCL reacting with PHCSO in the presence of stannous octoatecatalyst. The regioselective graft modification of CSO could be done through this methodof graft polymerization. It was found that the graft content of PCL in the graft copolymerincreased with increasing the mole ratio of ε-caprolactone to PHCSO. GPC confirmed themolecular weight distribution by indirect method was narrow. DSC results showed thatPHCSO-g-PCL (4ml ε-CL) was thermoplastic, its melting temperature was58.82℃. TGAanalysis showed that the thermoplastic graft copolymer had a high thermal stability, Thetemperature at5%weight loss of PHCSO-g-PCL (4ml ε-CL) was265℃. XRD analysisshowed that PHCSO-g-PCL was a crystalline graft copolymer. 3. A kind of thermoplastic copolymer of PHCSO-g-PCL-b-MPEG was synthesizedusing EDC·HCl as an activator, PHCSO as precursor and MPEG-b-PCL-COOH blockcopolymers. The grafting reaction route could not only implement the regioselective graftmodification of CSO, but also realizing the control of molecular weight and graft site.1HNMR indicated that molecular weight of MPEG-b-PCL block copolymer increased withthe increasing of the mole ratio of ε-caprolactone. GPC confirmed that the molecularweight distribution of MPEG-b-PCL, MPEG-b-PCL-COOH and PHCSO-g-PCL-b-MPEGwere narrow. DSC and TGA results showed that the crystallinity and thermal degradationtemperature of MPEG-b-PCL, MPEG-b-PCL-COOH and PHCSO-g-PCL-b-MPEG wereboth decreased gradually.4. PHCSO-g-PCL/PCL binary blends were prepared using solution blending, theirweight ratio were0:100、10:90、20:80、30:70、40:60、50:50and100:0, respectively.Biodegradable blending materials of LDPE/PHCSO-g-PCL/PCL were prepared using meltblending with LDPE and PHCSO-g-PCL/PCL of quality ratio (40/60), their weight ratiowere100:0、95:5、90:10、85:15and80:20. DSC showed that the compatibility of binarysolution blends (PHCSO-g-PCL/PCL) was the best when its weight ratio was40:60; Themechanical property test showed that the tensile strength of biodegradable blendingmaterials of LDPE/PHCSO-g-PCL/PCL increased with increasing the content ofPHCSO-g-PCL/PCL, however the elongation at break decreased, When the weight ratio ofLDPE/binary blends was85:15, tensile strength and elongation at break were the highest.TGA analysis showed that the thermal degradation temperature ofLDPE/PHCSO-g-PCL/PCL blending materials gradually reduced with increasing thecontent of PHCSO-g-PCL/PCL.