Temperature Dependence of Polymer Diffusion in MWCNT/PS Nanocomposites
Temperature Dependence of Polymer Diffusion in MWCNT/PS Nanocomposites
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DOI：
10.1021/ma302517x
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发表时间：
2013-03
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影响因子：
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通讯作者：
Wei-Shao Tung;N. Clarke;Russel C Composto;K. Winey
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文献类型：
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作者：
Wei-Shao Tung;N. Clarke;Russel C Composto;K. Winey
聚合物示踪剂在多壁碳纳米管/聚苯乙烯(PS)纳米复合材料中的扩散随多壁碳纳米管浓度的变化而变化，测量范围从152oC到214oC。在170C下，我们先前报道了示踪剂扩散系数在∼为2wt%MWCNT时出现的最小值；该浓度对应于通过线粘弹性测量的类固体行为的开始。用不含碳纳米管的示踪剂扩散系数(D_0)归一化的纳米复合材料中的示踪剂扩散系数(D)的最小值在较高温度下较浅，即214℃时(D/D_0)min=0.9,152℃时(D/D_0)min=0.6。利用我们的陷阱模型，这意味着在较高温度下，示踪剂扩散平行于和垂直于MWCNT的差异较小。最后，在固定的MWCNT浓度(0.5、2和6wt%)下，示踪剂扩散系数的温度依赖关系符合Williams-Landel-Ferry(WLF)方程，表明聚合物在纳米复合材料中的动力学被捕获。
Polymer tracer diffusion in multiwalled carbon nanotubes (MWCNT)/polystyrene (PS) nanocomposites as a function of MWCNT concentration was measured from 152 to 214 °C. At 170 °C, we previously reported a minimum in the tracer diffusion coefficient that occurs at ∼2 wt % MWCNT; this concentration corresponds to the onset of solidlike behavior as measured by linear viscoelasticity. The minimum in the tracer diffusion coefficient in the nanocomposites (D) normalized by the tracer diffusion coefficient without MWCNTs (D0) is shallower at higher temperatures, namely, (D/D0)min = 0.9 at 214 °C and (D/D0)min = 0.6 at 152 °C. Using our trap model, this implies that the difference between the tracer diffusion parallel and perpendicular to the MWCNT is smaller at higher temperatures. Finally, at fixed MWCNT concentrations (0.5, 2, and 6 wt %) the temperature dependence of the tracer diffusion coefficient follows the Williams–Landel–Ferry (WLF) equation, indicating that polymer dynamics in nanocomposites is captured ...