Synthesis, Characterization Of Novel Shape-memory Material

With the development of medical technology, growing number of novel humanizing therapeutic concepts, a new generation of biodegradable implant materials combining degradability with multi-functionalities is needed to be developed. The degradable polymers with shape-memory effect are considered to be potential candidates for the next generation of implant materials. In this thesis, several kinds of degradable polyurethanes and polyesters with shape-memory effect were synthesized. The shape-memory capabilities of these materials have been lucubrated. Firstly, glycolide and D,L-lactide were synthesized from glycolic acid and D,L-lactic acid, respectively. The high purity of glycolide and D,L-lactide was affirmed by fourier transform infrared (FTIR) spectrometry and proton nuclear magnetic resonance (1H-NMR) spectrometry. Secondly, under the protection of nitrogen gas, the star-shaped hydroxy-telechelic cooligoesters (poly(lactide-glycollide), PLGA) were synthesized via ring-opening polymerization at 130℃, using lactide and glycollide as comonomers, pentaerythritol as initiator and dibutyltin oxide (DBTO) as catalyst. The result of hydroxy titration and 1H-NMR reflects the structure of oligomer accorded with design specification. Then, poly(lactide-glycolide) tetracrylate (PLGA-TA) was synthesized by PLGA, acrylic chloride, and triethylamine in the tetrahydrofuran (THF) solvent. The result of FTIR and 1H-NMR shows that the rate of transformation is between 85% and 92%. The rate has reached the design specification. Finally, under the ultraviolet irradiation PLGA-TA and poly(ethylene glycol) dimethacrylate (PEGDMA) had been photopolzmerized to form crosslinked networks with benzil dimethyl ketal as photoinitiator.By the cyclic thermomechanical investigation, we found that the strain recovery rate is very high, while, with increasing the content of glycolide the strain fix rate decreased.At the same test conditions, when the material has high molecular weight, it needs more time to recover the deformed strain; when the material has high content of glycolide, the strain recovery time decreases.By the differential scanning calorimetry investigation, we analyzed the change of glass transformation temperature (Tg). The material prepared from higher molecular weight has lower Tg; the material with high glycolide content and PEGDMA content has lower Tg.