Chremos Alexandros, Douglas Jack F
Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Ann Phys. 2017 May;529(5). doi: 10.1002/andp.201600342. Epub 2017 Mar 23.
The properties of materials largely reflect the degree and character of the localization of the molecules comprising them so that the study and characterization of particle localization has central significance in both fundamental science and material design. Soft materials are often comprised of deformable molecules and many of their unique properties derive from the distinct nature of particle localization. We study localization in a model material composed of soft particles, hard nanoparticles with grafted layers of polymers, where the molecular characteristics of the grafted layers allow us to "tune" the softness of their interactions. Soft particles are particular interesting because spatial localization can occur such that density fluctuations on large length scales are suppressed, while the material is disordered at intermediate length scales; such materials are called "disordered hyperuniform". We use molecular dynamics simulation to study a liquid composed of polymer-grafted nanoparticles (GNP), which exhibit a reversible self-assembly into dynamic polymeric GNP structures below a temperature threshold, suggesting a liquid-gel transition. We calculate a number of spatial and temporal correlations and we find a significant suppression of density fluctuations upon cooling at large length scales, making these materials promising for the practical fabrication of "hyperuniform" materials.
材料的性质在很大程度上反映了构成它们的分子的局域化程度和特征，因此颗粒局域化的研究和表征在基础科学和材料设计中都具有核心意义。软材料通常由可变形分子组成，它们的许多独特性质源于颗粒局域化的独特性质。我们研究了一种由软颗粒、带有聚合物接枝层的硬纳米颗粒组成的模型材料中的局域化，其中接枝层的分子特性使我们能够“调节”它们相互作用的柔软度。软颗粒特别有趣，因为可能会发生空间局域化，从而抑制大长度尺度上的密度涨落，而材料在中间长度尺度上是无序的；这种材料被称为“无序超均匀”材料。我们使用分子动力学模拟来研究由聚合物接枝纳米颗粒（GNP）组成的液体，这些颗粒在低于温度阈值时会可逆地自组装成动态聚合物GNP结构，这表明存在液-凝胶转变。我们计算了一些空间和时间相关性，发现冷却时在大长度尺度上密度涨落会受到显著抑制，这使得这些材料有望用于“超均匀”材料的实际制造。
