生物可降解聚胺酯形狀記憶彈性體之性質分析與機制

Abstract

在形狀記憶材料中，擁有生物可降解特性的溫感性形狀記憶彈性體在生醫應用上有相當大的潛力。本篇研究中，形狀記憶彈性體是利用poly(-caprolactone) (PCL) oligodiol 和 poly(L-lactic acid) (PLLA) oligodiol兩種軟鏈段以不同比例調整鏈段結晶度，並最佳化形狀記憶性質最好的形狀記憶聚胺酯。一系列的聚胺酯透過差式掃描量熱儀(differential scanning calorimeter,DSC)、X-ray繞射( X-ray diffraction ,XRD)和小角度散射( small angle X-ray scattering,SAXS)分析聚胺酯的結晶。接著，更進一步結合拉力機和原位即時小角/廣角散射(in situ SAXS/WAXS)分析聚胺酯在形狀記憶過程中不同狀態下的結晶行為，並解釋形狀記憶的機制。在2D SAXS圖上的菱形表示順向結晶的生成，有助於固定形狀，並進一步說明恢復是依靠非晶鏈段的彈性。38 wt% PCL 和 25 wt% PLLA組成的聚胺酯能夠在37°C的水中達到恢復率近100%。此外，形狀記憶聚胺酯也有良好的內皮細胞存活率和較低的血小板活化程度。

Thermally induced shape memory is an attractive feature of certain functional materials. Among the shape memory polymers, shape memory elastomers (SMEs) especially those with biodegradability have great potential in the biomedical field. In this study, we prepared waterborne biodegradable polyurethane SME based on poly(-caprolactone) (PCL) oligodiol and poly(L-lactic acid) (PLLA) oligodiol as the mixed soft segments. The ratio of the soft segments in polyurethanes was optimized for shape memory behavior. The thermally induced shape memory mechanism of the series of polyurethanes was clarified using differential scanning calorimeter (DSC), X-ray diffraction (XRD), and small angle X-ray scattering (SAXS). In particular, the in situ SAXS measurements combined with shape deformation processes were employed to examine the stretch-induced (oriented) crystalline structure of the polyurethanes and to elucidate the unique mechanism for shape memory properties. The polyurethane with optimized PLLA crystalline segments showed a diamond-shape two-dimensional SAXS pattern after being stretched, which gave rise to better shape fixing and shape recovery. The shape memory behavior was further tested in 37°C water. The biodegradable polyurethane comprising 38 wt% PCL segments and 25 wt% PLLA segments and synthesized at a relatively lower temperature by the waterborne procedure showed ~100% shape recovery in 37°C water. The biodegradable polyurethane SME also demonstrated good endothelial cell viability as well as low platelet adhesion/activation. We conclude that the waterborne biodegradable polyurethane SME possesses a unique thermally induced shape memory mechanism and may have potential applications in making shape memory biodegradable stents or scaffolds.