Dramatic improvements in toughness in poly(lactide-co-glycolide) nanocomposites.
Dramatic improvements in toughness in poly(lactide-co-glycolide) nanocomposites.
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DOI：
10.1002/smll.200701231
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发表时间：
2008-05
期刊：
影响因子：
13.3
通讯作者：
Wei Xu;S. Raychowdhury;D. Jiang;H. Retsos;E. Giannelis
中科院分区：
文献类型：
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作者：
Wei Xu;S. Raychowdhury;D. Jiang;H. Retsos;E. Giannelis
聚（丙交酯-共-乙交酯）（PLG）是一种生物相容性和可生物降解的聚合物，通过添加少量表面改性的粘土纳米颗粒可以显着增韧。拉伸试验期间的伸长率从纯聚合物的7%增加到纳米复合材料的210%，伴随着模量的适度增加。相比之下，基于用六甲基二硅氮烷处理的气相二氧化硅的PLG纳米复合材料仅显示出适度的韧性改善。电子显微镜，X-射线散射，流变仪，和介电弛豫谱被用来研究增韧机制。屈服后粘土纳米复合材料发生多重银纹化。小角X射线散射研究表明，显着的粘土纳米粒子的取向沿着拉伸应力方向在变形过程中。粘土纳米复合材料显示出一种新的，缓慢的松弛模式，最有可能是由于界面吸附的PLG链的粘土纳米颗粒的表面上。韧性的急剧增加归因于由粘土纳米颗粒引入的物理交联，这是PLG/二氧化硅纳米复合材料中不存在的机制。物理交联增加了聚合物的脆性断裂强度，因此，通过多次银纹化和剪切屈服触发增韧机制。
Poly(lactide-co-glycolide) (PLG), a biocompatible and biodegradable polymer, is dramatically toughened by adding small amounts of surface modified clay nanoparticles. The elongation during tensile tests increases from 7% for the pure polymer to 210% for the nanocomposite, accompanied with a modest increase in modulus. In contrast, PLG nanocomposites based on fumed silica treated with hexamethyldisilazane show only modest improvements in toughness. Electron microscopy, X-ray scattering, rheometry, and dielectric relaxation spectroscopy are used to investigate the toughening mechanism. Multiple crazing occurs in the clay nanocomposite after yielding. Small angle X-ray scattering studies show significant orientation of the clay nanoparticles along the tensile stress direction during deformation. The clay nanocomposites show a new, slow relaxation mode, most likely due to interfacial adsorbption of PLG chains on the surface of the clay nanoparticles. The dramatic increase in toughness is attributed to physical crosslinks introduced by the clay nanoparticles, a mechanism absent in the PLG/silica nanocomposites. The physical crosslinks increase the brittle fracture strength of the polymer and, consequently, trigger a toughening mechanism via multiple crazing and shear yielding.