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Diffusion of Nanoparticles with Activated Hopping in Crowded Polymer Solutions
journal contribution
posted on 2020-04-01, 21:03 authored by Chundong Xue, Xinghua Shi, Yu Tian, Xu Zheng, Guoqing HuA long-distance
hop of diffusive nanoparticles (NPs) in crowded
environments was commonly considered unlikely, and its characteristics
remain unclear. In this work, we experimentally identify the occurrence
of the intermittent hops of large NPs in crowded entangled poly(ethylene
oxide) (PEO) solutions, which are attributed to thermally induced
activated hopping. We show that the diffusion of NPs in crowded solutions
is considered as a superposition of the activated hopping and the
reptation of the polymer solution. Such activated hopping becomes
significant when either the PEO molecular weight is large enough or
the NP size is relatively small. We reveal that the time-dependent
non-Gaussianity of the NP diffusion is determined by the competition
of the short-time relaxation of a polymer entanglement strand, the
activated hopping, and the long-time reptation. We propose an exponential
scaling law τhop/τe ∼ exp(d/dt) to characterize the hopping
time scale, suggesting a linear dependence of the activated hopping
energy barrier on the dimensionless NP size. The activated hopping
motion can only be observed between the onset time scale of the short-time
relaxation of local entanglement strands and the termination time
scale of the long-time relaxation. Our findings on activated hopping
provide new insights into long-distance transportation of NPs in crowded
biological environments, which is essential to the delivery and targeting
of nanomedicines.