Wu Di, Narayanan Suresh, Li Ruhao, Feng Yi, Akcora Pinar
Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA.
Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA.
Soft Matter. 2023 Apr 12;19(15):2764-2770. doi: 10.1039/d2sm01617f.
The entanglements of dynamically asymmetric polymer layers influence relaxations of nanoparticles in polymer nanocomposites. In this work, the dynamics of polymer-adsorbed and polymer-grafted nanoparticles in a poly(methyl acrylate) matrix polymer was investigated using X-ray photon correlation spectroscopy (XPCS) to understand the role of chain rigidity and chemical heterogeneities in particle dynamics. Locations of dynamic heterogeneities close to nanoparticles and away from particle surfaces were examined with the comparison of adsorbed and grafted nanoparticles. Our results show that the chemical heterogeneities around dispersed nanoparticles transitioned the particle dynamics from Brownian diffusion into hyperdiffusion, and moreover, the high rigidity of chains in the chemically heterogeneous interfacial layers slowed down the particle dynamics. The hyperdiffusion measured both in grafted particles and adsorbed particles was attributed to the dense interfacial mixing of dynamically heterogeneous chains.
动态不对称聚合物层的缠结会影响聚合物纳米复合材料中纳米颗粒的弛豫。在这项工作中，使用X射线光子相关光谱法（XPCS）研究了聚（甲基丙烯酸甲酯）基体聚合物中聚合物吸附和聚合物接枝纳米颗粒的动力学，以了解链刚性和化学不均匀性在颗粒动力学中的作用。通过比较吸附和接枝的纳米颗粒，研究了靠近纳米颗粒和远离颗粒表面的动态不均匀性的位置。我们的结果表明，分散纳米颗粒周围的化学不均匀性使颗粒动力学从布朗扩散转变为超扩散，此外，化学不均匀界面层中链的高刚性减缓了颗粒动力学。接枝颗粒和吸附颗粒中测得的超扩散归因于动态不均匀链的密集界面混合。
