Local Viscosity of Interfacial Layers in Polymer Nanocomposites Measured by Magnetic Heating
Local Viscosity of Interfacial Layers in Polymer Nanocomposites Measured by Magnetic Heating
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DOI：
10.1021/acsapm.0c00889
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发表时间：
2020-12
期刊：
影响因子：
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通讯作者：
Di Wu;D. Weiblen;R. Ozisik;Pinar Akcora
中科院分区：
文献类型：
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作者：
Di Wu;D. Weiblen;R. Ozisik;Pinar Akcora
已知聚合物链和纳米颗粒之间的界面吸引力的强度控制聚合物纳米复合材料中链的流动性和粘弹性能。我们选择了磁性纳米颗粒周围的界面层，由两种不同的可混溶聚合物组成，并测量了能量吸收率，因为颗粒在高频交变磁场下旋转时会耗散能量。使用经典的吸收模型从测量的旋转弛豫时间计算局部粘度。局部粘度的变化归因于吸附的聚合物的刚性和它们的界面层的化学不均匀性。最高的粘度测量与灵活的，较短的吸附聚（甲基丙烯酸甲酯）链。聚（丙烯酸甲酯）和高刚性的聚合物，如聚（2-乙烯基吡啶），和聚（双酚A碳酸酯）之间的弱界面允许颗粒容易地旋转在扩散模式，产生最低的粘度，匹配的未缠结的基质聚合物的粘度预测。纳米颗粒周围界面层的化学和动力学不均匀性高度依赖于链的刚性。测量界面聚合物层的局部粘度对于聚合物纳米复合材料中的应力传递、增强和热导率的界面层控制机制是必不可少的。
The strength of interfacial attractions between polymer chains and nanoparticles is known to control the mobility of chains and viscoelastic properties in polymer nanocomposites. We chose the interfacial layers around magnetic nanoparticles to consist of two different miscible polymers and measured the energy absorption rates as particles dissipate energy while they rotate under a high-frequency alternating magnetic field. Local viscosities were calculated from the measured rotational relaxation times using the classical absorption model. The changes in local viscosities were attributed to the rigidity of adsorbed polymers and chemical heterogeneities of their interfacial layers. The highest viscosity was measured with the flexible, shorter adsorbed poly(methyl methacrylate) chains. The weak interphases between poly(methyl acrylate) and highly rigid polymers such as poly(2-vinyl pyridine), and poly(bisphenol A carbonate) allowed particles to rotate easily in a diffusive mode, yielding the lowest viscosity that matched to the viscosity prediction of an unentangled matrix polymer. Chemical and dynamic heterogeneity of interfacial layers around nanoparticles highly depend on the rigidity of chains. Measuring the local viscosity of interfacial polymer layers is essential for interfacial layer-controlled mechanisms of stress transfer, reinforcement, and thermal conductivity in polymer nanocomposites.