Segmental Diffusion in Attractive Polymer Nanocomposites: A Quasi-Elastic Neutron Scattering Study
Segmental Diffusion in Attractive Polymer Nanocomposites: A Quasi-Elastic Neutron Scattering Study
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DOI：
10.1021/acs.macromol.8b01716
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发表时间：
2019-01-22
期刊：
影响因子：
5.5
通讯作者：
Winey, Karen I.
中科院分区：
文献类型：
--
作者：
Bailey, Eric J.;Griffin, Philip J.;Winey, Karen I.
本文采用准弹性中子散射（QENS）技术，系统地研究了由聚（2-乙烯基吡啶）（P2VP）和直径26 nm的胶体二氧化硅纳米颗粒（NPs）组成的模型吸引聚合物纳米复合材料的片段动力学。与大多数动态测量不同，QENS提供小长度尺度（类似于1nm）和快速时间尺度（类似于1ns）的空间和时间信息，因此在远高于玻璃化转变的温度下。我们发现在这些长度和时间尺度上，即使在平均粒子间距为库恩长度数量级的极端约束下，经典的平移扩散也能很好地描述P2VP段运动。在最高的NP浓度（50 vol %）下，平均段扩散系数随NP浓度的增加而单调降低，近似为5。有趣的是，这种片段动力学的降低非常弱地依赖于P2VP的分子量，从未纠缠态（10 kg/mol）到高度纠缠态（190 kg/mol）。这与在较低温度下有充分记录的分子量对吸引聚合物纳米复合材料段动力学的影响形成对比。
We present a systematic study of segmental dynamics in model attractive polymer nanocomposites comprising poly(2-vinylpyridine) (P2VP) and 26 nm diameter colloidal silica nanoparticles (NPs) using quasi-elastic neutron scattering (QENS). Unlike most dynamic measurements, QENS provides both spatial and temporal information about small length scales (similar to 1 nm) and fast time scales (similar to 1 ns) and therefore at temperatures far above the glass transition. We find that on these length and time scales P2VP segmental motion is well-described by classic translational diffusion even under extreme confinement, where the average interparticle spacing is on the order of the Kuhn length. The average segmental diffusion coefficient decreases monotonically with increasing NP concentration by up to a factor of similar to 5 at the highest NP concentrations (50 vol %). Interestingly, this reduction in segmental dynamics is very weakly dependent on P2VP molecular weight spanning the unentangled (10 kg/mol) to the highly entangled regimes (190 kg/mol). This stands in contrast to the well-documented molecular weight effect on segmental dynamics in attractive polymer nanocomposites at lower temperatures.