Poly(ethylene oxide)/silica nanocomposites: Structure and rheology
Poly(ethylene oxide)/silica nanocomposites: Structure and rheology
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DOI：
10.1021/la026338j
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发表时间：
2002-12-24
期刊：
影响因子：
3.9
通讯作者：
Archer, LA
中科院分区：
文献类型：
--
作者：
Zhang, Q;Archer, LA
以窄分子量分布的聚氧化乙烯（PEO）为原料，研究了聚合物-颗粒和颗粒-颗粒相互作用对纳米复合材料粘弹性能的影响。纳米复合材料是使用“冷冻干燥”方法制备的，以保证二氧化硅的均匀分散。用原子力显微镜相衬成像表征了二氧化硅纳米球的分散状态，用机械流变仪研究了这些材料在熔融状态下的弛豫动力学和粘弹性能。线性粘弹性数据表明，在低振荡频率下，颗粒体积分数0低至2%，大大低于理论逾渗阈值（φ类似于30%）的固体状响应的过渡。纳米粒子的体积分数，表面化学，和PEO分子量都被发现强烈影响纳米复合材料的结构和动力学。一个填料网络机制，其中纳米级的二氧化硅颗粒周围的固定化壳的PEO是由大得多的聚合物分子桥接，提出来解释我们的观察。
The effects of polymer-particle and particle-particle interactions on viscoelastic properties of nanocomposite materials are investigated using narrow molecular weight distribution poly(ethylene oxide) (PEO) containing isotropic silica nanospheres. Nanocomposites are prepared using a "freeze-drying" method to guarantee homogeneous dispersion of silica. The dispersion state of silica nanospheres is characterized by atomic force microscopy phase contrast imaging, and mechanical rheometry is used to study relaxation dynamics and viscoelastic properties of these materials in the melt state. Linear viscoelastic data indicate a transition to a solidlike response at low oscillation frequencies for particle volume fractions 0 as low as 2%, dramatically lower than the theoretical percolation threshold (phi similar to 30%). Nanoparticle volume fraction, surface chemistry, and PEO molecular weight are all found to strongly influence nanocomposite structure and dynamics. A filler networking mechanism, wherein nanosized silica particles surrounded by an immobilized shell of PEO are bridged by much larger polymer molecules, is proposed to explain our observations.