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-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，该材料的聚合物链与硅氧烷纳米粒子之间以共价键结合。针对该生物相容性体系的结构特征、热性能与化学稳定性，本研究采用傅里叶变换红外光谱（Fourier-Transform Infrared Spectroscopy, FTIR）、拉曼光谱（Raman Spectroscopy）、29Si核磁共振（29 Si 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）开展了系统表征。扫描电子显微镜与小角X射线散射测试结果表明，硅氧烷结点可作为聚合物链间的交联点，促进PLA与PEO之间的相容性。傅里叶变换红外光谱、拉曼光谱、X射线衍射、差示扫描量热法及热重分析的结果证实，硅氧烷纳米粒子的引入可降低两种聚合物的结晶度，并提升其热稳定性。上述表征技术还发现，该体系中聚合物间的高相容性可增强PLA的热稳定性，并抑制其结晶过程。除了因PLA低结晶度而具备无脆性的特性外，该新型材料还展现出优异的水溶液中PLA降解抗性：这一特性一方面源于硅氧烷粒子可作为水扩散的屏障，另一方面则归功于亲水的PEO链段能够吸附水分子，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。