School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil Ulsan 44919, Republic of Korea.
Institut für Physik-NMR, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Straβe 7, D-06120 Halle, Germany.
Phys Rev Lett. 2019 Oct 18;123(16):167801. doi: 10.1103/PhysRevLett.123.167801.
Unusual structures and dynamic properties found in polymer nanocomposites (PNCs) are often attributed to immobilized (adsorbed) polymers at nanoparticle-polymer interfaces, which are responsible for reducing the intrinsic incompatibility between nanoparticles and polymers in PNCs. Although tremendous effort has been made to characterize the presence of immobilized polymers, a systematic understanding of the structure and dynamics under different processing conditions is still lacking. Here, we report that the initial dispersing solvent, which is not present after producing PNCs, drives these nonequilibrium effects on polymer chain dynamics at interfaces. Employing extensive small-angle scattering, proton NMR spectroscopy, and rheometry experiments, we found that the thickness of the immobilized layer can be dependent on the initial solvent, changing the structure and the properties of the PNC significantly. In addition, we show that the outcome of the initial solvent effect becomes more effective at particle volume fractions where the immobile layers begin to interact.
聚合物纳米复合材料（PNC）中发现的不寻常结构和动态特性通常归因于纳米粒子-聚合物界面处固定（吸附）的聚合物，这些聚合物负责降低 PNC 中纳米粒子与聚合物之间的固有不相容性。尽管已经做出了巨大的努力来表征固定聚合物的存在，但对于不同加工条件下的结构和动力学的系统理解仍然缺乏。在这里，我们报告说，初始分散溶剂在产生 PNC 后不再存在，这会对界面上聚合物链动力学的非平衡效应产生影响。通过广泛的小角散射、质子 NMR 光谱和流变学实验，我们发现固定层的厚度可以依赖于初始溶剂，从而显著改变 PNC 的结构和性能。此外，我们还表明，在固定层开始相互作用的颗粒体积分数下，初始溶剂效应的结果变得更加有效。
