Synthesis and characterization of a new Polylactic acid-Siloxane- Polyethylene oxide organic-inorganic nanocomposite presenting simultaneously high thermal stability, high resistance to degradation and absence of brittleness

This work presents the synthesis, structural investigation and some properties of a new PLA-Siloxane-PEO hybrid presenting covalent bonds between polymers and siloxane nanoparticles.The structural features, thermal properties and chemical stability of this biocompatible system have been studied by Fourier-Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, 29 Si Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (MEV), X-Ray Diffraction (XRD), Small-Angle X-ray Scattering (SAXS), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). SEM and SAXS measurements showed that the siloxane nodes act as crosslinks between the polymer chains promoting miscibility between PLA and PEO. FTIR, Raman XRD, DSC and TGA results evidenced that presence of the siloxane nanoparticles diminishes crystallinity of both polymers and increases their thermal resistance. The same techniques also showed that the high miscibility between polymers in this system enhances PLA thermal stability and prejudices PLA crystallization. Among the absence of brittleness due to the low crystalline character of PLA, this new material exhibits a fantastic resistance to PLA degradation in aqueous medium, attributed both to the presence of the siloxane particles acting as a barrier towards water diffusion and to the hydrophilic PEO segments which may attract water molecules, preventing PLA hydrolysis. All these characteristics open amazing perspective for use of this hybrid material in biological and pharmaceutical applications.本研究报道了一种新型聚乳酸（Polylactic Acid, PLA）-硅氧烷（Siloxane）-聚环氧乙烷（Polyethylene Oxide, PEO）杂化材料的合成、结构表征及其部分性能，该材料中聚合物与硅氧烷纳米粒子之间通过共价键结合。该生物相容性体系的结构特征、热性能及化学稳定性通过以下表征手段开展研究：傅里叶变换红外光谱（Fourier-Transform Infrared Spectroscopy, FTIR）、拉曼光谱（Raman Spectroscopy）、硅-29核磁共振（29Si Nuclear Magnetic Resonance, NMR）、扫描电子显微镜（Scanning Electron Microscopy, MEV）、X射线衍射（X-Ray Diffraction, XRD）、小角X射线散射（Small-Angle X-ray Scattering, SAXS）、热重分析（Thermogravimetric Analysis, TGA）以及差示扫描量热法（Differential Scanning Calorimetry, DSC）。扫描电子显微镜与小角X射线散射测试结果表明，硅氧烷结点作为聚合物链间的交联点，促进了PLA与PEO之间的相容性。FTIR、拉曼光谱、XRD、DSC及TGA结果证实，硅氧烷纳米粒子的存在降低了两种聚合物的结晶度，并提升了其热稳定性。上述表征手段还显示，该体系中聚合物间的高相容性提升了PLA的热稳定性，同时抑制了PLA的结晶过程。鉴于PLA因低结晶度而无脆性问题，该新型材料在水介质中展现出优异的抗PLA降解性能，这一特性可归因于两点：一是硅氧烷粒子作为屏障阻碍水分子扩散，二是亲水的PEO链段可吸附水分子，从而阻止PLA的水解反应。上述所有特性为该杂化材料在生物及医药领域的应用开辟了广阔前景。