Wang Dapeng, Chin Huai-Ying, He Chunlin, Stoykovich Mark P, Schwartz Daniel K
Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309, United States.
ACS Macro Lett. 2016 Apr 19;5(4):509-514. doi: 10.1021/acsmacrolett.6b00183. Epub 2016 Apr 4.
Previous studies of polymer motion at solid/liquid interfaces described the transport in the context of a continuous time random walk (CTRW) process, in which diffusion switches between desorption-mediated "flights" (i.e., hopping) and surface-adsorbed waiting-time intervals. However, it has been unclear whether the waiting times represented periods of complete immobility or times during which molecules engaged in a different (e.g., slower or confined) mode of interfacial transport. Here we designed high-throughput, single-molecule tracking measurements to address this question. Specifically, we studied polymer dynamics on either chemically homogeneous or nanopatterned surfaces (hexagonal diblock copolymer films) with chemically distinct domains, where polymers were essentially excluded from the low-affinity domains, eliminating the possibility of significant continuous diffusion in the absence of desorption-mediated flights. Indeed, the step-size distributions on homogeneous surfaces exhibited an additional diffusive mode that was missing on the chemically heterogeneous nanopatterned surfaces, confirming the presence of a slow continuous mode due to 2D in-plane diffusion. Kinetic Monte Carlo simulations were performed to test this model and, with the theoretical in-plane diffusion coefficient of = 0.20 μm/s, we found a good agreement between simulations and experimental data on both chemically homogeneous and nanopatterned surfaces.
先前关于聚合物在固/液界面运动的研究，是在连续时间随机游走（CTRW）过程的背景下描述其输运的，在该过程中，扩散在解吸介导的“飞行”（即跳跃）和表面吸附的等待时间间隔之间切换。然而，尚不清楚这些等待时间是代表完全静止的时期，还是分子进行不同（例如，较慢或受限）界面输运模式的时期。在这里，我们设计了高通量单分子追踪测量来解决这个问题。具体而言，我们研究了聚合物在化学性质均一或具有化学性质不同区域的纳米图案化表面（六方双嵌段共聚物薄膜）上的动力学，在这些表面上，聚合物基本上被排除在低亲和力区域之外，排除了在没有解吸介导飞行的情况下发生显著连续扩散的可能性。实际上，均一表面上的步长分布呈现出一种在化学性质不均匀的纳米图案化表面上不存在的额外扩散模式，证实了由于二维平面内扩散而存在缓慢连续模式。进行了动力学蒙特卡罗模拟以测试该模型，并且在理论平面内扩散系数为 = 0.20 μm/s的情况下，我们发现模拟结果与化学性质均一和纳米图案化表面上的实验数据之间具有良好的一致性。
