Jiao Yang, Akcora Pinar
Department of Chemical Engineering & Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Oct;90(4):042601. doi: 10.1103/PhysRevE.90.042601. Epub 2014 Oct 17.
Polystyrene-grafted iron oxide nanoparticles have been shown to phase separate into ordered morphologies of strings, well-dispersed particles, and spherical aggregates at low graft densities in polymer matrices. In this work, small-angle neutron scattering experiments are performed to reveal the role of grafted chain conformation on nanoparticle assemblies. We demonstrate that chains grafted at low densities follow Gaussian statistics at any dispersion states. These results suggest that grafted chains are not distorted but remain Gaussian when particles are aggregated into strings. Small-angle x-ray and neutron scattering results show that matrix chains do not influence the formation of strings, but have a significant impact on the size and internal structure of aggregated particles. We conclude that spherical aggregates of nanoparticles with low polymer graft densities are akin to interpenetrating networks in which free matrix chains bridge the fractals of particles and control the cluster density.
已表明，在聚合物基质中，低接枝密度下的聚苯乙烯接枝氧化铁纳米颗粒会相分离成有序的形态，如链状、分散良好的颗粒和球形聚集体。在这项工作中，进行了小角中子散射实验，以揭示接枝链构象对纳米颗粒组装体的作用。我们证明，低密度接枝的链在任何分散状态下都遵循高斯统计。这些结果表明，当颗粒聚集成链时，接枝链不会变形，而是保持高斯状态。小角X射线和中子散射结果表明，基质链不影响链的形成，但对聚集颗粒的尺寸和内部结构有显著影响。我们得出结论，低聚合物接枝密度的纳米颗粒球形聚集体类似于互穿网络，其中自由基质链桥接颗粒的分形并控制簇密度。
